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  • 1.
    Gustavson, Stefan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    2D Shape Rendering by Distance Fields2012In: OpenGL Insights: OpenGL, OpenGL ES, and WebGL community experiences / [ed] Patrick Cozzi and Christophe Riccio, CRC Press, 2012, 173-182 p.Chapter in book (Other academic)
    Abstract [en]

    We present a method for real time rendering of anti-aliased curved contours, combining recent results from research on distance transforms and modern GPU shading using GLSL. The method is capable of rendering glyphs and symbols of very high quality at arbitrary levels of magnification and minification, and it is both versatile and easy to use.

  • 2.
    Engelson, Vadim
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    3D graphics and Modelica: an integrated approach2000In: Linköping Electronic Articles in Computer and Information Science, ISSN 1401-9841, Vol. 5, no 9Article in journal (Refereed)
    Abstract [en]

    The Modelica standard library and available Modelica tools contain some facilities for specification of 3D geometry and 3D graphics. Geometry and graphics is associated with physical objects included in simulated Modelica models. However, important graphics properties are missing from this model. In particular, physical objects cannot change their shape (geometry) and rendering features (graphics) dynamically. The physics of simulation, is often not affected by geometry of physical objects. For instance, a body is often approximated by its center of mass under certain conditions. Either simple predefined shapes or specifications of geometry via external files are used. The last facility leads to separation between the model and the corresponding graphics and geometry. Our proposal is to integrate 3D geometric and graphical features with Modelica models of physical objects. The 3D graphics information is specified explicitly via annotations containing certain graphics primitives or using instances from a specially designed geometry class library. The motivation, syntax and implementation outline for this approach are discussed in this report.

  • 3.
    Johansson, Erik
    Linköping University, Department of Electrical Engineering.
    3D Reconstruction of Human Faces from Reflectance Fields2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    Human viewers are extremely sensitive to the appearanceof peoples faces, which makes the rendering of realistic human faces a challenging problem. Techniques for doing this have continuously been invented and evolved since more than thirty years.

    This thesis makes use of recent methods within the area of image based rendering, namely the acquisition of reflectance fields from human faces. The reflectance fields are used to synthesize and realistically render models of human faces.

    A shape from shading technique, assuming that human skin adheres to the Phong model, has been used to estimate surface normals. Belief propagation in graphs has then been used to enforce integrability before reconstructing the surfaces. Finally, the additivity of light has been used to realistically render the models.

    The resulting models closely resemble the subjects from which they were created, and can realistically be rendered from novel directions in any illumination environment.

  • 4.
    Lång, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    3D Teleconferencing: The construction of a fully functional, novel 3D Teleconferencing system2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report summarizes the work done to develop a 3D teleconferencing system, which enables remote participants anywhere in the world to be scanned in 3D, transmitted and displayed on a constructed 3D display with correct vertical and horizontal parallax, correct eye contact and eye gaze. The main focus of this report is the development of this system and especially how to in an efficient and general manner render to the novel 3D display. The 3D display is built out of modified commodity hardware and show a 3D scene for observers in up to 360 degrees around it and all heights. The result is a fully working 3D Teleconferencing system, resembling communication envisioned in movies such as holograms from Star Wars. The system transmits over the internet, at similar bandwidth requirements as concurrent 2D videoconferencing systems.

  • 5.
    Ernvik, Aron
    Linköping University, Department of Electrical Engineering.
    3D visualization of weather radar data2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    There are 12 weather radars operated jointly by smhi and the Swedish Armed Forces in Sweden. Data from them are used for short term forecasting and analysis. The traditional way of viewing data from the radars is in 2D images, even though 3D polar volumes are delivered from the radars. The purpose of this work is to develop an application for 3D viewing of weather radar data.

    There are basically three approaches to visualization of volumetric data, such as radar data: slicing with cross-sectional planes, surface extraction, and volume rendering. The application developed during this project supports variations on all three approaches. Different objects, e.g. horizontal and vertical planes, isosurfaces, or volume rendering objects, can be added to a 3D scene and viewed simultaneously from any angle. Parameters of the objects can be set using a graphical user interface and a few different plots can be generated.

    Compared to the traditional 2D products used by meteorologists when analyzing radar data, the 3D scenes add information that makes it easier for the users to understand the given weather situations. Demonstrations and discussions with meteorologists have rendered positive reactions. The application will be installed and evaluated at Arlanda airport in Sweden.

  • 6.
    Persson, Anders
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    3D volume rendering helical CT cholangiography2002In: 3rd Int'l Workshop on Multislice CT 3D Imaging Virtual Endoscopy, Rom, juni 2002,2002, 2002Conference paper (Refereed)
  • 7.
    Persson, Anders
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    3D volume rendering helical CT cholangiography. A new method to visualise normal and obstructed bile ducts.2002In: The Museum of Medical History, Stockholm, maj 2002,2002, 2002Conference paper (Refereed)
  • 8.
    Persson, Anders
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    3D-Volume-Rendering Helical CT cholangiography (Rome, June6-8, 2002; Springer Verlag)2002In: Syllabus 3rd international workshop on:Multislice CT, 3D Imaging, virtual endoscopy, Linköping: Linköpings universitet , 2002, 107-109 p.Chapter in book (Other academic)
  • 9.
    Höst, Gunnar E.
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Schönborn, Konrad J.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A Case-Based Study of Students' Visuohaptic Experiences of Electric Fields around Molecules: Shaping the Development of Virtual Nanoscience Learning Environments2013In: Education Research International, ISSN 2090-4002, E-ISSN 2090-4010, Vol. 2013, 194363Article in journal (Refereed)
    Abstract [en]

    Recent educational research has suggested that immersive multisensory virtual environments offer learners unique and exciting knowledge-building opportunities for the construction of scientific knowledge. This paper delivers a case-based study of students’ immersive interaction with electric fields around molecules in a multisensory visuohaptic virtual environment. The virtual architecture presented here also has conceptual connections to the flourishing quest in contemporary literature for the pressing need to communicate nanoscientific ideas to learners. Five upper secondary school students’ prior conceptual understanding of electric fields and their application of this knowledge to molecular contexts, were probed prior to exposure to the virtual model. Subsequently, four students interacted with the visuohaptic model while performing think-aloud tasks. An inductive and heuristic treatment of videotaped verbal and behavioural data revealed distinct interrelationships between students’ interactive strategies implemented when executing tasks in the virtual system and the nature of their conceptual knowledge deployed. The obtained qualitative case study evidence could serve as an empirical basis for informing the rendering and communication of overarching nanoscale ideas. At the time of composing this paper for publication in the current journal, the research findings of this study have been put into motion in informing a broader project goal of developing educational virtual environments for depicting nanophenomena.

  • 10.
    Sultana, Kishwar
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    ul Hasan, Kamran
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Alvi, N, H.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Klason, P.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A comparative study of the electrodeposition and the aqueous chemical growth techniques for the utilization of ZnO nanorods on p-GaN for white light emitting diodes2011In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 49, no 1, 32-42 p.Article in journal (Refereed)
    Abstract [en]

    Vertically well aligned zinc oxide nanorods (ZnO NRs) were grown on p-GaN by electrodeposition (ED) and aqueous chemical growth (ACG) techniques and the structures were employed to fabricate white light emitting diodes (LEDs). Room temperature current voltage (IV), photoluminescence (PL), and electroluminescence (EL) measurements were performed to investigate and compare both LEDs. In general, the IV characteristics and the PL spectra of both LEDs were rather similar. Nevertheless, the EL of the ED samples showed an extra emission peak shoulder at 730 nm. Moreover, at the same injection current, the EL spectrum of the ED light emitting diode showed a small UV shift of 12 nm and its white peak was found to be broader when compared to the ACG grown LED. The broadening of the EL spectrum of the LED grown by ED is due to the introduction of more radiative deep level defects. The presented LEDs have shown excellent color rendering indexes reaching a value as high as 95. These results indicate that the ZnO nanorods grown by both techniques possess very interesting electrical and optical properties but the ED is found to be faster and more suitable for the fabrication of white LEDs.

  • 11.
    Ek, Joel
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    A Data-Parallel Graphics Pipeline Implemented in OpenCL2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report documents implementation details, results, benchmarks and technical discussions for the work carried out within a master’s thesis at Linköping University. Within the master’s thesis, the field of software rendering is explored in the age of parallel computing. Using the Open Computing Language, a complete graphics pipeline was implemented for use on general processing units from different vendors. The pipeline is tile-based, fully-configurable and provides means of rendering visually compelling images in real-time. Yet, further optimizations for parallel architectures are needed as uneven work loads drastically decrease the overall performance of the pipeline.

  • 12.
    Henriksson, Ola
    Linköping University, Department of Science and Technology.
    A Depth of Field Algorithm for Realtime 3D Graphics in OpenGL2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    The company where this thesis was formulated constructs VR applications for the medical environment. The hardware used is ordinary dektops with consumer level graphics cards and haptic devices. In medicin some operations require microscopes or cameras. In order to simulate these in a virtual reality environment for educational purposes, the effect of depth of field or focus have to be considered.

    A working algorithm that generates this optical occurence in realtime, stereo rendered computer graphics is presented in this thesis. The algorithm is implemented in OpenGL and C++ to later be combined with a VR application simulating eye-surgery which is built with OpenGL Optimizer.

    Several different approaches are described in this report. The call for realtime stereo rendering (~60 fps) means taking advantage of the graphics hardware to a great extent. In OpenGL this means using the extensions to a specific graphic chip for better performance, in this case the algorithm is implemented for a GeForce3 card.

    To increase the speed of the algorithm much of the workload is moved from the CPU to the GPU (Graphics Processing Unit). By re-defining parts of the ordinary OpenGL pipeline via vertex programs, a distance-from-focus map can be stored in the alpha channel of the final image with little time loss.

    This can effectively be used to blend a previously blurred version of the scene with a normal render. Different techniques to quickly blur a renderedimage is discussed, to keep the speed up solutions that require moving data from the graphics card is not an option.

  • 13.
    Solli, Martin
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A Font Search Engine for Large Font Databases2011In: ELCVIA Electronic Letters on Computer Vision and Image Analysis, ISSN 1577-5097, Vol. 10, no 1, 24-41 p.Article in journal (Refereed)
    Abstract [en]

    A search engine for font recognition is presented and evaluated. The intended usage is the search in very large font databases. The input to the search engine is an image of a text line, and the output is the name of the font used when rendering the text. After pre-processing and segmentation of the input image, a local approach is used, where features are calculated for individual characters. The method is based on eigenimages calculated from edge filtered character images, which enables compact feature vectors that can be computed rapidly. In this study the database contains 2763 different fonts for the English alphabet. To resemble a real life situation, the proposed method is evaluated with printed and scanned text lines and character images. Our evaluation shows that for 99 % of the queries, the correct font name can be found within the five best matches.

  • 14.
    Klein, Richard
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, The Tema Institute, Centre for Climate Science and Policy Research . Linköping University, Faculty of Arts and Sciences. Stockholm Environment Institute, Sweden.
    Juhola, Sirkku
    University of Helsinki, Finland; Aalto University, Finland .
    A framework for Nordic actor-oriented climate adaptation research2014In: Environmental Science and Policy, ISSN 1462-9011, E-ISSN 1873-6416, Vol. 40, 101-115 p.Article in journal (Refereed)
    Abstract [en]

    The past ten years have seen a substantial increase in research on climate change adaptation, but a large gap remains between adaptation research and action. Adaptation researchers have either failed to demonstrate the relevance of their findings to practitioners and policymakers, or stakeholders have based their views and decisions on other kinds of information. In addition, in sectors such as agriculture, forestry, nature conservation, urban planning, water management and energy supply, adaptation has been studied separately from mitigation, which contradicts the reality of many practitioners. This paper identifies five bottlenecks to the use of adaptation research in adaptation practice and policy. These bottlenecks have gone unnoticed because the traditional framing of adaptation does not adequately consider the notion of agency, often rendering stakeholder interactions ineffective. Knowledge and use of actor-oriented theory when analysing and discussing adaptation needs and options could serve to find ways to overcome the bottlenecks and narrow the gap between research and action. The paper presents a novel framework for actor-oriented adaptation research that is being conducted within the Nordic Centre of Excellence for Strategic Adaptation Research (NORD-STAR). It frames climate adaptation as addressing both the impacts of climate change and the consequences of climate policy. Two methodological approaches - modelling and visualisation, and policy analysis - are applied to three thematic issues: land-use change, energy transitions, and insurance and finance.

  • 15.
    Eklund, Anders
    et al.
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Friman, Ola
    Fraunhofer Mevis, Bremen, Germany.
    Andersson, Mats
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Knutsson, Hans
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    A GPU accelerated interactive interface for exploratory functional connectivity analysis of FMRI data2011In: Image Processing (ICIP), 2011, IEEE , 2011, 1589-1592 p.Conference paper (Refereed)
    Abstract [en]

    Functional connectivity analysis is a way to investigate how different parts of the brain are connected and interact. A common measure of connectivity is the temporal correlation between a reference voxel time series and all the other time series in a functional MRI data set. An fMRI data set generally contains more than 20,000 within-brain voxels, making a complete correlation analysis between all possible combinations of voxels heavy to compute, store, visualize and explore. In this paper, a GPU-accelerated interactive tool for investigating functional connectivity in fMRI data is presented. A reference voxel can be moved by the user and the correlations to all other voxels are calculated in real-time using the graphics processing unit (GPU). The resulting correlation map is updated in real-time and visualized as a 3D volume rendering together with a high resolution anatomical volume. This tool greatly facilitates the search for interesting connectivity patterns in the brain.

  • 16.
    Mensmann, Jörg
    et al.
    University of Münster, Germany.
    Ropinski, Timo
    University of Münster, Germany.
    Hinrichs, Klaus
    University of Münster, Germany.
    A GPU-Supported Lossless Compression Scheme for Rendering Time-Varying Volume Data2010In: VG'10 Proceedings of the 8th IEEE/EG international conference on Volume Graphics, IEEE , 2010, 109-116 p.Conference paper (Refereed)
    Abstract [en]

    Since the size of time-varying volumetric data sets typically exceeds the amount of available GPU and main memory, out-of-core streaming techniques are required to support interactive rendering. To deal with the performance bottlenecks of hard-disk transfer rate and graphics bus bandwidth, we present a hybrid CPU/GPU scheme for lossless compression and data streaming that combines a temporal prediction model, which allows to exploit coherence between time steps, and variable-length coding with a fast block compression algorithm. This combination becomes possible by exploiting the CUDA computing architecture for unpacking and assembling data packets on the GPU. The system allows near-interactive performance even for rendering large real-world data sets with a low signal-to-noise-ratio, while not degrading image quality. It uses standard volume raycasting and can be easily combined with existing acceleration methods and advanced visualization techniques.

  • 17.
    Hendeby, Gustaf
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Hol, Jeroen
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Karlsson, Rickard
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Graphics Processing Unit Implementation of the Particle Filter2007Report (Other academic)
    Abstract [en]

    Modern graphics cards for computers, and especially their graphics processing units (GPUs), are designed for fast rendering of graphics. In order to achieve this GPUs are equipped with a parallel architecture which can be exploited for general-purpose computing on GPU (GPGPU) as a complement to the central processing unit (CPU). In this paper GPGPU techniques are used to make a parallel GPU implementation of state-of-the-art recursive Bayesian estimation using particle filters (PF). The modifications made to obtain a parallel particle filter, especially for the resampling step, are discussed and the performance of the resulting GPU implementation is compared to one achieved with a traditional CPU implementation. The resulting GPU filter is faster with the same accuracy as the CPU filter for many particles, and it shows how the particle filter can be parallelized.

  • 18.
    Hendeby, Gustaf
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Hol, Jeroen
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Karlsson, Rickard
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Graphics Processing Unit Implementation of the Particle Filter2007In: Proceedings of the 15th European Statistical Signal Processing Conference, European Association for Signal, Speech, and Image Processing , 2007, 1639-1643 p.Conference paper (Refereed)
    Abstract [en]

    Modern graphics cards for computers, and especially their graphics processing units (GPUs), are designed for fast rendering of graphics. In order to achieve this GPUs are equipped with a parallel architecture which can be exploited for general-purpose computing on GPU (GPGPU) as a complement to the central processing unit (CPU). In this paper GPGPU techniques are used to make a parallel GPU implementation of state-of-the-art recursive Bayesian estimation using particle filters (PF). The modifications made to obtain a parallel particle filter, especially for the resampling step, are discussed and the performance of the resulting GPU implementation is compared to one achieved with a traditional CPU implementation. The resulting GPU filter is faster with the same accuracy as the CPU filter for many particles, and it shows how the particle filter can be parallelized.

  • 19.
    Fries, Jakob
    et al.
    Linköping University, Department of Electrical Engineering, Computer Engineering.
    Johansson, Simon
    Linköping University, Department of Electrical Engineering, Computer Engineering.
    A Modular 3D Graphics Accelerator for FPGA2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A modular and area-efficient 3D graphics accelerator for tile based rendering in FPGA systems has been designed and implemented. The accelerator supports a subset of OpenGL, with features such as mipmapping, multitexturing and blending. The accelerator consists of a software component for projection and clipping of triangles, as well as a hardware component for rasterization, coloring and video output. Trade-offs made between area, performance and functionality have been described and justified. In order to evaluate the functionality and performance of the accelerator, it has been tested with two different applications.

  • 20.
    Samini, Ali
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    A perspective geometry approach to user-perspective rendering in hand-held video see-through augmented reality2014In: VRST '14 Proceedings of the 20th ACM Symposium on Virtual Reality Software and Technology, SPRINGER-VERLAG BERLIN , 2014, 207-208 p.Conference paper (Refereed)
    Abstract [en]

    Video see-through Augmented Reality (V-AR) displays a video feed overlaid with information, co-registered with the displayed objects. In this paper we consider the type of V-AR that is based on a hand-held device with a fixed camera. In most of the VA-R applications the view displayed on the screen is completely determined by the orientation of the camera, i.e., the device-perspective rendering; the screen displays what the camera sees. The alternative method is to use the relative pose of the user's view and the camera, i.e., the user-perspective rendering. In this paper we present an approach to the user perspective V-AR using 3D projective geometry. The view is adjusted to the user's perspective and rendered on the screen, making it an augmented window. We created and tested a running prototype based on our method.

  • 21.
    Fall, Andreas
    et al.
    Department of Fiber Technology, KTH.
    Lindström, Stefan B
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    Sprakel, Joris
    Wågberg, Lars
    Department of Fiber Technology, KTH.
    A physical cross-linking process of cellulose nanofibril gels with shear-controlled fibril orientation2013In: Soft Matter, ISSN 1744-683X, Vol. 9, 1852-1863 p.Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils constitute the smallest fibrous components of wood, with a width of approximately 4 nm and a length in the micrometer range. They consist of aligned linear cellulose chains with crystallinity exceeding 60%, rendering stiff, high-aspect-ratio rods. These properties are advantageous in the reinforcement components of composites. Cross-linked networks of fibrils can be used as templates into which a polymer enters. In the semi-concentrated regime (i.e. slightly above the overlap concentration), carboxy methylated fibrils dispersed in water have been physically cross-linked to form a volume-spanning network (a gel) by reducing the pH or adding salt, which diminishes the electrostatic repulsion between fibrils. By applying shear during or after this gelation process, we can orient the fibrils in a preferred direction within the gel, for the purpose of fully utilizing the high stiffness and strength of the fibrils as reinforcement components. Using these gels as templates enables precise control of the spatial distribution and orientation of the dispersed phase of the composites, optimizing the potentially very large reinforcement capacity of the nanofibrils.

  • 22.
    Abrahamsson, Lars
    Linköping University, Department of Electrical Engineering.
    A portal based system for indoor environs2006Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    The purpose of this thesis is to document the development of the graphics part of an extremely pluggable game engine/lab environment for a course in advanced game programming. This thesis is one out of five, and concerns indoor, realtime computer 3D graphics. It covers state-of-the-art techniques such as GLSL - the OpenGL Shading Language - and more well known techniques such as portal based rendering.

  • 23.
    Bakos, Niklas
    Linköping University, Department of Science and Technology.
    A Prototype For An Interactive And Dynamic Image-Based Relief Rendering System2002Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    In the research of developing arbitrary and unique virtual views from a real- world scene, a prototype of an interactive relief texture mapping system capable of processing video using dynamic image-based rendering, is developed in this master thesis. The process of deriving depth from recorded video using binocular stereopsis is presented, together with how the depth information is adjusted to be able to manipulate the orientation of the original scene. When the scene depth is known, the recorded organic and dynamic objects can be seen from viewpoints not available in the original video.

  • 24.
    Johansson, Jimmy
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Cooper, Matthew
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    A screen space quality method for data abstraction2008In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, Vol. 27, no 3, 1039-1046 p.Article in journal (Refereed)
    Abstract [en]

    The rendering of large data sets can result in cluttered displays and non-interactive update rates, leading to time consuming analyses. A straightforward solution is to reduce the number of items, thereby producing an abstraction of the data set. For the visual analysis to remain accurate, the graphical representation of the abstraction must preserve the significant features present in the original data. This paper presents a screen space quality method, based on distance transforms, that measures the visual quality of a data abstraction. This screen space measure is shown to better capture significant visual structures in data, compared with data space measures. The presented method is implemented on the GPU, allowing interactive creation of high quality graphical representations of multivariate data sets containing tens of thousands of items. © 2008 The Eurographics Association and Blackwell Publishing Ltd.

  • 25.
    Persson, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lindblom, Maria
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Jackowski, Christian
    Institute of Legal Medicine, University of Zürich, Schweiz.
    A state-of-the-art pipeline for postmortem CT and MRI visualization: from data acquisition to interactive image interpretation at autopsy2011In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 52, no 5, 522-536 p.Article, review/survey (Refereed)
    Abstract [en]

    The importance of autopsy procedures leading to the establishment of the cause of death is well-known. A recent addition to the autopsy work flow is the possibility of conducting postmortem imaging, in its 3D version also called virtual autopsy (VA), using multidetector computed tomography (MDCT) or magnetic resonance imagining (MRI) data from scans of cadavers displayed with direct volume rendering (DVR) 3D techniques. The use of the data and their workflow are presented. Data acquisition was performed and high quality data-sets with submillimeter precision were acquired. New data acquisition techniques such as dualenergy CT (DECT) and quantitative MRI, then were implemented and provided additional information. Particular findings hardly visualized in conventional autopsy can rather easy be seen at the full body CT, such as air distribution, e.g. pneumothorax, pneumopericardium, air embolism, and wound channels. MRI shows natural deaths such as myocardial infarctions. Interactive visualization of these 3D data-sets can provide valuable insight into the corpses and enables non-invasive diagnostic procedures. In postmortem CT imaging, not being limited by a patient depending radiation dose limit the data-sets can, however, be generated with such a high resolution that they become difficult to handle in today’s archive retrieval and interactive visualization systems, specifically in the case of full body scans. To take full advantage of these new technologies the postmortem workflow needs to be tailored to the demands and opportunities that the new technologies allow.

  • 26.
    Samini, Ali
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    A study on improving close and distant device movement pose manipulation for hand-held augmented reality2016In: VRST '16 Proceedings of the 22nd ACM Conference on Virtual Reality Software and Technology, ACM Press, 2016, 121-128 p.Conference paper (Refereed)
    Abstract [en]

    Hand-held smart devices are equipped with powerful processing units, high resolution screens and cameras, that in combination makes them suitable for video see-through Augmented Reality. Many Augmented Reality applications require interaction, such as selection and 3D pose manipulation. One way to perform intuitive, high precision 3D pose manipulation is by direct or indirect mapping of device movement.

    There are two approaches to device movement interaction; one fixes the virtual object to the device, which therefore becomes the pivot point for the object, thus makes it difficult to rotate without translate. The second approach avoids latter issue by considering rotation and translation separately, relative to the object's center point. The result of this is that the object instead moves out of view for yaw and pitch rotations.

    In this paper we study these two techniques and compare them with a modification where user perspective rendering is used to solve the rotation issues. The study showed that the modification improves speed as well as both perceived control and intuitiveness among the subjects.

  • 27.
    Jönsson, Daniel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Sundén, Erik
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Ropinski, Timo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A Survey of Volumetric Illumination Techniques for Interactive Volume Rendering2014In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, Vol. 33, no 1, 27-51 p.Article in journal (Refereed)
    Abstract [en]

    Interactive volume rendering in its standard formulation has become an increasingly important tool in many application domains. In recent years several advanced volumetric illumination techniques to be used in interactive scenarios have been proposed. These techniques claim to have perceptual benefits as well as being capable of producing more realistic volume rendered images. Naturally, they cover a wide spectrum of illumination effects, including varying shading and scattering effects. In this survey, we review and classify the existing techniques for advanced volumetric illumination. The classification will be conducted based on their technical realization, their performance behaviour as well as their perceptual capabilities. Based on the limitations revealed in this review, we will define future challenges in the area of interactive advanced volumetric illumination.

  • 28.
    Samini, Ali
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Lundin Palmerius, Karljohan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    A User Study on Touch Interaction for User-Perspective Rendering in Hand-Held Video See-Through Augmented Reality2016In: Augmented Reality, Virtual Reality, and Computer Graphics: Third International Conference, AVR 2016, Lecce, Italy, June 15-18, 2016. Proceedings, Part II, Springer, 2016, 304-317 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a user study on touch interaction with hand-held Video See-through Augmented Reality (V-AR). In particular, the commonly used Device Perspective Rendering (DPR) is compared with User Perspective Rendering (UPR) with respect to both performance and user experience and preferences. We present two user study tests designed to mimic the tasks that are used in various AR applications.

    Looking for an object and selecting when it’s found, is one of the most used tasks in AR software. Our first test focuses on comparing UPR and DPR in a simple find and selection task. Manipulating the pose of a virtual object is another commonly used task in AR. The second test focuses on multi-touch interaction for 6 DoF object pose manipulation through UPR and DPR.

  • 29.
    Eilertsen, Gabriel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Larsson, Per
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Unger, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A versatile material reflectance measurement system for use in production2011In: Proceedings of SIGRAD 2011. Evaluations of Graphics and Visualization — Efficiency, Usefulness, Accessibility, Usability, November 17–18, 2011, KTH, Stockholm, Sweden, Linköping University Electronic Press, 2011, 69-76 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we present our developed bidirectional reflectance distribution capturing pipeline. It includes a constructed gonioreflectometer for reflectance measurements, as well as extensive software for operation, data visualization and parameter fitting of analytic models. Our focus is on the flexible user interface, aimed at material appearance creation for computer graphics, and targeted both for production and research employment.

    Key challenges have been in providing a user friendly and effective software for functioning in a production environment, abstracting the details of the calculations involved in the reflectance capturing and fitting. We show how a combination of well-tuned tools can make complex processes such as reflectance calibration, measurement and fitting highly automated in a fast and easy work-flow, from material scanning to model parameters optimized for use in rendering. At the same time, the developed software provides a modifiable interface for detailed control. The importance of having good reflectance visualizations is also demonstrated, where the software plotting tools are able to show vital details of a reflectance distribution, giving valuable insight in to a materials properties and a models accuracy of fit to measured data, on both a local and global level.

  • 30.
    Kratz, Andrea
    et al.
    Zuse Institute Berlin.
    Meier, Björn
    Zuse Institue Berlin.
    Hotz, Ingrid
    Zuse Institue Berlin.
    A Visual Approach to Analysis of Stress Tensor Fields2011In: Scientific Visualization: Interactions, Features, Metaphors, Dagstuhl Follow-Ups, ISSN 1868-8977, Vol. 2, 188-211 p.Article in journal (Refereed)
    Abstract [en]

    We present a visual approach for the exploration of stress tensor fields. In contrast to common tensor visualization methods that only provide a single view to the tensor field, we pursue the idea of providing various perspectives onto the data in attribute and object space. Especially in the context of stress tensors, advanced tensor visualization methods have a young tradition. Thus, we propose a combination of visualization techniques domain experts are used to with statistical views of tensor attributes. The application of this concept to tensor fields was achieved by extending the notion of shape space. It provides an intuitive way of finding tensor invariants that represent relevant physical properties. Using brushing techniques, the user can select features in attribute space, which are mapped to displayable entities in a three-dimensional hybrid visualization in object space. Volume rendering serves as context, while glyphs encode the whole tensor information in focus regions. Tensorlines can be included to emphasize directionally coherent features in the tensor field. We show that the benefit of such a multi-perspective approach is manifold. Foremost, it provides easy access to the complexity of tensor data. Moreover, including well-known analysis tools, such as Mohr diagrams, users can familiarize themselves gradually with novel visualization methods. Finally, by employing a focus-driven hybrid rendering, we significantly reduce clutter, which was a major problem of other three-dimensional tensor visualization methods. 

  • 31.
    Löw, Joakim
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kronander, Joel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Ynnerman, Anders
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Unger, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    ABC - BRDF Models for Accurate and Efficient Rendering of Glossy Surfaces2013In: Eurographics 24th Symposium on Rendering: Posters, 2013Conference paper (Other academic)
    Abstract [en]

    Glossy surface reflectance is hard to model accuratley using traditional parametric BRDF models. An alternative is provided by data driven reflectance models, however these models offers less user control and generally results in lower efficency. In our work we propose two new lightweight parameteric BRDF models for accurate modeling of glossy surface refllectance, one inspired by Rayleigh-Rice theory for optically smooth surfaces and one inspired by microfacet-theory. We base our models on a thourough study of the scattering behaviour of measured reflectance data from the MERL database. The study focuses on two key aspects of BRDF models, parametrization and scatter distribution. We propose a new scattering distributuion for glossy BRDFs inspired by the ABC model for surface statistics of optically smooth surfaces. Based on the survey we consider two parameterizations, one based on micro-facet theory using the halfway vector and one inspired by the parametrization for the Rayleigh-Rice BRDF model considering the projected devaition vector. To enable efficent rendering we also show how the new models can be approximatley sampled for importance sampling the scattering integral.

  • 32.
    Lindemann, Florian
    et al.
    University of Munster.
    Ropinski, Timo
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    About the Influence of Illumination Models on Image Comprehension in Direct Volume Rendering2011In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 17, no 12, 1922-1931 p.Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a user study in which we have investigated the influence of seven state-of-the-art volumetric illumination models on the spatial perception of volume rendered images. Within the study, we have compared gradient-based shading with half angle slicing, directional occlusion shading, multidirectional occlusion shading, shadow volume propagation, spherical harmonic lighting as well as dynamic ambient occlusion. To evaluate these models, users had to solve three tasks relying on correct depth as well as size perception. Our motivation for these three tasks was to find relations between the used illumination model, user accuracy and the elapsed time. In an additional task, users had to subjectively judge the output of the tested models. After first reviewing the models and their features, we will introduce the individual tasks and discuss their results. We discovered statistically significant differences in the testing performance of the techniques. Based on these findings, we have analyzed the models and extracted those features which are possibly relevant for the improved spatial comprehension in a relational task. We believe that a combination of these distinctive features could pave the way for a novel illumination model, which would be optimized based on our findings.

  • 33.
    Cervin, Albert
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Adaptive Hardware-accelerated Terrain Tessellation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis report, a scheme for adaptive hardware terrain tessellation is presented. The scheme uses an offline processing approach where a height map is analyzed in terms of curvature and the result is stored in a resource called density map. This density map is then bound as a resource to the hardware tessellation stage and used to bias the tessellation factor for a given edge. The scheme is implemented inside FrostbiteTM2 by EATM DICETM and produces good results while making the heightfield rendering more efficient. The performance gain can be used to increase the rendering detail, allowing for better visual appearance for the terrain mesh. The scheme is currently implemented for hardware tessellation but could also be used for software terrain mesh generation. The implementation works satisfactory and produces good results with a reasonable speed.

  • 34.
    Zeitler, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Adaptive rendering of celestial bodies in WebGL2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report covers theory and comparison of techniques for rendering massive scale 3D geospa- tial planet data in a web browser. It also presents implementation details of a few of these tech- niques in WebGL and Javascript, using the Three.js [1] 3D library. The thesis project is part of the implementation of Unitea, a web based education platform for interactive astronomy visualizations. Unitea is a derivative of Uniview, which is a fulldome interactive simulation of the universe. A major part of this thesis is dedicated to the implementa- tion of Hierarchical Level of Detail (HLOD) modules for Three.js based on the theory presented by T. Ulrich [2] and later generalized by Cozzi and Ring [3]. HLOD techniques are dynamic level of detail algorithms that represent the surface of objects as accurately as possible from a certain viewing angle. By using space partitioning tree-structures, view based error metrics and culling techniques detailed representations of the objects (in this case planets) can be efficiently rendered in real-time. The modules developed provide a general-purpose library for rendering planets (or other spher- ical objects) with dynamic level of detail in Three.js. The library also features connections to online web map services (WMS) and tile services.

  • 35.
    Ljung, Patric
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Adaptive Sampling in Single Pass, GPU-based Raycasting of Multiresolution Volumes2006In: Proceedings Eurographics/IEEE International Workshop on Volume Graphics 2006, Boston, USA, 2006, 39-46 p.Conference paper (Other academic)
    Abstract [en]

    This paper presents a novel direct volume rendering technique for adaptive object- and image-space sampling density of multiresolution volumes. The raycasting is implemented entirely on the GPU in a single pass fragment program which adapts the sampling density along rays, guided by block resolutions. The multiresolution volumes are provided by a transfer function based level-of-detail scheme adaptively loading large out-of-core volumes. Adaptive image-space sampling is achieved by gathering projected basic volume block statistics for screen tiles and then allocating a level-of-detail for each tile. This combination of techniques provides a significant reduction of processing requirements while maintaining high quality rendering.

  • 36.
    Åström, Freddie
    et al.
    Heidelberg Collaboratory for Image Processing Heidelberg University Heidelberg, Germany.
    Felsberg, Michael
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Scharr, Hanno
    BG-2: Plant Sciences Forschungszentrum Jülich 52425, Jülich, Germany.
    Adaptive sharpening of multimodal distributions2015In: Colour and Visual Computing Symposium (CVCS), 2015 / [ed] Marius Pedersen and Jean-Baptiste Thomas, IEEE , 2015, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    In this work we derive a novel framework rendering measured distributions into approximated distributions of their mean. This is achieved by exploiting constraints imposed by the Gauss-Markov theorem from estimation theory, being valid for mono-modal Gaussian distributions. It formulates the relation between the variance of measured samples and the so-called standard error, being the standard deviation of their mean. However, multi-modal distributions are present in numerous image processing scenarios, e.g. local gray value or color distributions at object edges, or orientation or displacement distributions at occlusion boundaries in motion estimation or stereo. Our method not only aims at estimating the modes of these distributions together with their standard error, but at describing the whole multi-modal distribution. We utilize the method of channel representation, a kind of soft histogram also known as population codes, to represent distributions in a non-parametric, generic fashion. Here we apply the proposed scheme to general mono- and multimodal Gaussian distributions to illustrate its effectiveness and compliance with the Gauss-Markov theorem.

  • 37. Srinivasan, Seshadri
    et al.
    Ljung, Patric
    Linköping University, Department of Science and Technology, Media and Information Technology. Siemens Corporation.
    McDermott, Bruce A
    Smith-Casem, Merv Mencias
    Adaptive volume rendering for ultrasound color flow diagnostic imaging2013Patent (Other (popular science, discussion, etc.))
  • 38.
    Junker, Johan
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Plastic Surgery, Hand Surgery and Burns. Linköping University, Faculty of Health Sciences.
    Sommar, Pehr
    Linköping University, Department of Clinical and Experimental Medicine, Plastic Surgery, Hand Surgery and Burns. Linköping University, Faculty of Health Sciences.
    Skog, Mårten
    Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Johnson, Hans
    Department of Surgery, Section of Plastic Surgery and Burn Center, Haukeland University Hospital, Bergen , Norway.
    Kratz, Gunnar
    Linköping University, Department of Clinical and Experimental Medicine, Plastic Surgery, Hand Surgery and Burns. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Sinnescentrum, Department of Plastic Surgery, Hand surgery UHL.
    Adipogenic, Chondrogenic and Osteogenic Differentiation of ClonallyDerived Human Dermal Fibroblasts2010In: Cells Tissues Organs, ISSN 1422-6405, E-ISSN 1422-6421, Vol. 191, no 2, 105-118 p.Article in journal (Refereed)
    Abstract [en]

    The apparent need of an autologous cell source for tissueengineering applications has led researchers to explore thepresence of cells with stem cell plasticity in several humantissues. Dermal fibroblasts (FBs) are easy to harvest, expandin vitro and store, rendering them plausible candidates forcell-based therapies. The aim of the present study was toobserve the effects of adipogenic, chondrogenic and osteogenicinduction media on the phenotype of human FBs.Human preadipocytes obtained from fat tissue have beenproposed as an adult stem cell source with suitable characteristics,and were used as control cells in regard to their differentiationpotential. Routine staining, immunohistochemicalanalysis and alkaline phosphatase assay were employed,in order to study the phenotypic shift. FBs were shown topossess multilineage potential, giving rise to fat-, cartilageandbone-like cells. To exclude contaminant progenitor cellsor cell fusion giving rise to tissue with adipocyte-, chondrocyte-and osteoblast-like cells, single-cell cloning was performed.Single-cell-cloned FBs (sccFBs) displayed a similardifferentiation potential as primary-culture FBs. The pres-ence of ‘stem-cell-specific’ surface antigens was analyzedusing flow cytometry. The results reveal that sccFBs haveseveral of the markers associated with cells exhibiting stemcell plasticity. The findings presented here are corroboratedby the findings of other groups, and suggest the use of humandermal FBs in cell-based therapies for the reconstructionof fat, cartilage and bone.

  • 39.
    Silén, Charlotte
    et al.
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Kvist, Joanna
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Health Sciences.
    Nylander, Eva
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Fyrénius, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Clinical Physiology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Advanced 3D visualization in student-centred medical education2008In: Medical teacher, ISSN 0142-159X, E-ISSN 1466-187X, Vol. 30, no 5, e115-e124 p.Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Healthcare students have difficulties achieving a conceptual understanding of 3D anatomy and misconceptions about physiological phenomena are persistent and hard to address. 3D visualization has improved the possibilities of facilitating understanding of complex phenomena. A project was carried out in which high quality 3D visualizations using high-resolution CT and MR images from clinical research were developed for educational use. Instead of standard stacks of slices (original or multiplanar reformatted) volume-rendering images in the quicktime VR format that enables students to interact intuitively were included. Based on learning theories underpinning problem based learning, 3D visualizations were implemented in the existing curricula of the medical and physiotherapy programs. The images/films were used in lectures, demonstrations and tutorial sessions. Self-study material was also developed. AIMS: To support learning efficacy by developing and using 3D datasets in regular health care curricula and enhancing the knowledge about possible educational value of 3D visualizations in learning anatomy and physiology. METHOD: Questionnaires were used to investigate the medical and physiotherapy students' opinions about the different formats of visualizations and their learning experiences. RESULTS: The 3D images/films stimulated the students will to understand more and helped them to get insights about biological variations and different organs size, space extent and relation to each other. The virtual dissections gave a clearer picture than ordinary dissections and the possibility to turn structures around was instructive. CONCLUSIONS: 3D visualizations based on authentic, viable material point out a new dimension of learning material in anatomy, physiology and probably also pathophysiology. It was successful to implement 3D images in already existing themes in the educational programs. The results show that deeper knowledge is required about students' interpretation of images/films in relation to learning outcomes. There is also a need for preparations and facilitation principles connected to the use of 3D visualizations.

  • 40.
    Hadwiger, Markus
    et al.
    VRVis Research Center, Vienna, Austria.
    Ljung, Patric
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Siemens Corporate Research, Princeton, USA.
    Rezk Salama, Christof
    University of Siegen, Germany.
    Ropinski, Timo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. University of M¨unster, Germany.
    Advanced illumination techniques for GPU volume raycasting2008In: ACM Siggraph Asia 2008 Courses, 2008, 1-11 p.Conference paper (Refereed)
    Abstract [en]

    Volume raycasting techniques are important for both visual arts and visualization. They allow an efficient generation of visual effects and the visualization of scientific data obtained by tomography or numerical simulation. Thanks to their flexibility, experts agree that GPU-based raycasting is the state-of-the art technique for interactive volume rendering. It will most likely replace existing slice-based techniques in the near future. Volume rendering techniques are also effective for the direct rendering of implicit surfaces used for soft body animation and constructive solid geometry.

    The lecture starts off with an in-depth introduction to the concepts behind GPU-based ray-casting to provide a common base for the following parts. The focus of this course is on advanced illumination techniques which approximate the physically-based light transport more convincingly. Such techniques include interactive implementation of soft and hard shadows, ambient occlusion and simple Monte-Carlo based approaches to global illumination including translucency and scattering. With the proposed techniques, users are able to interactively create convincing images from volumetric data whose visual quality goes far beyond traditional approaches. The optical properties in participating media are defined using the phase function. Many approximations to the physically based light transport applied for rendering natural phenomena such as clouds or smoke assume a rather homogenous phase function model. For rendering volumetric scans on the other hand different phase function models are required to account for both surface-like structures and fuzzy boundaries in the data. Using volume rendering techniques, artists who create medical visualization for science magazines may now work on tomographic scans directly, without the necessity to fall back to creating polygonal models of anatomical structures.

  • 41.
    Hadwiger, Markus
    et al.
    VRVis Research Center, Vienna, Austria.
    Ljung, Patric
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Siemens Corporate Research, Princeton, USA.
    Rezk-Salama, Christof
    University of Siegen, Germany.
    Ropinski, Timo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. University of Münster, Germany.
    Advanced Illumination Techniques for GPU-Based Volume Raycasting2009Other (Other academic)
    Abstract [en]

    Volume raycasting techniques are important for both visual arts and visualization. They allow an efficient generation of visual effects and the visualization of scientific data obtained by tomography or numerical simulation. Thanks to their flexibility, experts agree that GPU-based raycasting is the state-of-the art technique for interactive volume rendering. It will most likely replace existing slice-based techniques in the near future. Volume rendering techniques are also effective for the direct rendering of implicit surfaces used for soft body animation and constructive solid geometry.

    The lecture starts off with an in-depth introduction to the concepts behind GPU-based ray-casting to provide a common base for the following parts. The focus of this course is on advanced illumination techniques which approximate the physically-based light transport more convincingly. Such techniques include interactive implementation of soft and hard shadows, ambient occlusion and simple Monte-Carlo based approaches to global illumination including translucency and scattering. With the proposed techniques, users are able to interactively create convincing images from volumetric data whose visual quality goes far beyond traditional approaches. The optical properties in participating media are defined using the phase function. Many approximations to the physically based light transport applied for rendering natural phenomena such as clouds or smoke assume a rather homogenous phase function model. For rendering volumetric scans on the other hand different phase function models are required to account for both surface-like structures and fuzzy boundaries in the data. Using volume rendering techniques, artists who create medical visualization for science magazines may now work on tomographic scans directly, without the necessity to fall back to creating polygonal models of anatomical structures.

  • 42.
    Lindemann, Florian
    et al.
    University of Münster, Germany.
    Ropinski, Timo
    University of Münster, Germany.
    Advanced Light Material Interaction for Direct Volume Rendering2010In: VG'10 Proceedings of the 8th IEEE/EG international conference on Volume Graphics, IEEE , 2010, 101-108 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we present a heuristic approach for simulating advanced light material interactions in the context of interactive volume rendering. In contrast to previous work, we are able to incorporate complex material functions, which allow to simulate reflectance and scattering. We exploit a common representation of these material properties based on spherical harmonic basis functions, to combine the achieved reflectance and scattering effects with natural lighting conditions, i. e., incorporating colored area light sources. To achieve these goals, we introduce a modified SH projection technique, which is not just tailored at a single material category, but adapts to the present material. Thus, reflecting and scattering materials as assigned trough the transfer function can be captured in a unified approach. We will describe the required extensions to the standard volume rendering integral and present an approximation which allows to realize the material effects in order to achieve interactive frame rates. By exploiting a combination of CPU and GPU processing, we are able to modify material properties and can change the illumination conditions interactively. We will demonstrate the outcome of the proposed approach based on renderings of real-world data sets and report the achieved computation times.

  • 43.
    Felekidis, Dimitrios
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Advanced Visualization Techniques for Laparoscopic Liver Surgery2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Laparoscopic liver surgery is mainly preferred over the traditional open liver surgery due to its unquestionable benefits. This type of surgery is executed by inserting an endoscope camera and the surgical tools inside the patient’s body through small incisions. The surgeons perform the operation by watching the video transmitted from the endoscope camera to high-resolution monitors. The location of the tumors and cysts is examined before and during the operation by the surgeons from the pre-operative CT scans displayed on a different monitor or on printed copies making the operation more difficult to perform.

    In order to make it easier for the surgeons to locate the tumors and cysts and have an insight for the rest of the inner structures of the liver, the 3D models of the liver’s inner structures are extracted from the preoperative CT scans and are overlaid on to the live video stream transmitted from the endoscope camera during the operation, a technique known as virtual X-ray. In that way the surgeons can virtually look into the liver and locate the tumors and cysts (focus objects) and also have a basic understanding of their spatial relation with other critical structures. The current master thesis focuses on enhancing the depth and spatial perception between the focus objects and their surrounding areas when they are overlaid on to the live endoscope video stream. That is achieved by placing a cone on the position of each focus object facing the camera. The cone creates an intersection surface (cut volume) that cuts the structures that lay in it, visualizing the depth of the cut and the spatial relation between the focus object and the intersected structures. The positioning of the cones is calculated automatically according to the center points of the focus objects but the sizes of the cones are user defined with bigger sizes revealing more of the surrounding area. The rest of the structures that are not part of any cut volume are not discarded but handled in such way that still depict their spatial relation with the rest of the structures. Different rendering results are presented for a laparoscopic liver test surgery in which a plastic liver model was used. The results include different presets of the cut volumes’ characteristics. Additionally, the same technique can be applied on the 3D liver’s surface instead of the live endoscope image and provide depth and spatial information. Results from that case are also presented.

  • 44.
    Felekidis, Dimitrios
    et al.
    Scientific Visualization Group , Linköping University, Sweden.
    Steneteg, Peter
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Ropinski, Timo
    Visual Computing Group, Ulm University.
    Advanced visualization techniques for laparoscopic liver surgery2015In: Proceedings of SIGRAD 2015: June 1st and 2nd, Stockholm, Sweden / [ed] Christopher E. Peters, Lars Kjelldahl, Stockholm: Svenska föreningen för grafisk databehandling , 2015, 28-31 p.Conference paper (Refereed)
    Abstract [en]

    In order to make it easier for the surgeons to locate tumors during a laparoscopic liver surgery, and to form a mental image of the remaining structures, the 3D models of the liver’s inner structures are extracted from a preoperative CT scan and are overlaid onto the live video stream obtained during surgery. In that way the surgeons can virtually look into the liver and locate the tumors (focus objects) and also have a basic understanding of their spatial relation with other critical structures. Within this paper, we present techniques for enhancing the spatial comprehension of the focus objects in relation to their surrounding areas, while they are overlaid onto the live endoscope video stream. To obtain an occlusion-free view while not destroying the context, we place a cone on the position of each focus object facing the camera. The cone creates an intersection surface (cut volume) that cuts the structures, visualizing the depth of the cut and the spatial relation between the focus object and the intersected structures. Furthermore, we combine this technique with several rendering approaches, which have proven to be useful for enhancing depth perception in other scenarios.

  • 45.
    Bernhardsson, Susanne
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    Advancing evidence-based practice in primary care physiotherapy: Guideline implementation, clinical practice, and patient preferences2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Research on physiotherapy treatment interventions has increased dramatically in the past 25 years and it is a challenge to transfer research findings into clinical practice, so that patients benefit from effective treatment. Development of clinical practice guidelines is a potentially useful strategy to implement research evidence into practice. However, the impact of guideline implementation in Swedish primary care physiotherapy is unknown. To achieve evidence-based practice (EBP), research evidence should be integrated with clinical expertise and patient preferences, but knowledge is limited about these factors in Swedish primary care physiotherapy.

    The overall aim of this thesis was to increase understanding of factors of importance for the implementation of EBP in Swedish primary care physiotherapy. Specific aims were: to translate and adapt a questionnaire for the measurement of EBP and guidelines; to investigate physiotherapists’ attitudes, knowledge and behaviour related to EBP and guidelines; to examine clinical practice patterns; to evaluate the effects of a tailored guideline implementation strategy; and to explore patients’ preferences for physiotherapy.

    The thesis comprises four studies (A-D), reported in five papers. In Study A, a questionnaire for the measurement of EBP and guidelines was translated, cross-culturally adapted, and tested for validity (n=10) and reliability (n=42). Study B was a cross-sectional study in which this questionnaire was used to survey primary care physiotherapists in the county council Region Västra Götaland (n=271). In Study C, a strategy for the implementation of guidelines was developed and evaluated, using the same questionnaire (n=271 at baseline, n=256 at follow-up), in a prospective controlled trial. The strategy was based on an implementation model, was tailored to address the determinants of guideline use identified in Study B, and comprised several components including an educational seminar. Study D was an exploratory qualitative study of patients with musculoskeletal disorders (n=20), using qualitative content analysis.

    The validity and reliability of the questionnaire was found to be satisfactory. Most physiotherapists have a positive regard for EBP and guidelines, although these attitudes are not fully reflected in the reported use of guidelines. The most important determinants of  guideline use were considering guidelines important to facilitate practice and knowing how to integrate patient preferences with guidelines. The tailored, multi-component guideline implementation significantly affected awareness of, knowledge of, and access to guidelines. Use of guidelines was significantly affected among those who attended an implementation seminar. Clinical practice for common musculoskeletal conditions included interventions supported by evidence of various strengths as well as interventions with insufficient research evidence. The most frequently reported interventions were advice and exercise therapy. The interviewed patients expressed trust and confidence in the professionalism of physiotherapists and in the therapists’ ability to choose appropriate treatment, rendering treatment preferences subordinate. This trust seemed to foster active engagement in their physiotherapy.

    In conclusion: The adapted questionnaire can be used to reliably measure EBP in physiotherapy. The positive attitudes found do not necessarily translate to guideline use, due to several perceived barriers. The tailored guideline implementation strategy used can be effective to reduce barriers and contribute to increased use of guidelines. The clinical practice patterns identified suggest that physiotherapists rely both on research evidence and their clinical expertise when choosing treatment methods. Patients’ trust in their physiotherapist’s competence and preference for active engagement in their therapy need to be embraced by the clinician and, together with the therapist’s clinical expertise, integrated with guideline use in the clinical decision making. Further research is needed on how the EBP components and different knowledge sources can be integrated in physiotherapy practice, as well as on implementation effects on patient outcomes.

    List of papers
    1. Measuring Evidence-Based Practice in Physical Therapy: Translation, Adaptation, Further Development, Validation, and Reliability Test of a Questionnaire
    Open this publication in new window or tab >>Measuring Evidence-Based Practice in Physical Therapy: Translation, Adaptation, Further Development, Validation, and Reliability Test of a Questionnaire
    2013 (English)In: Physical Therapy, ISSN 0031-9023, E-ISSN 1538-6724, Vol. 93, no 6, 819-832 p.Article in journal (Refereed) Published
    Abstract [en]

    Background. Evidence-based practice (EBP) and evidence-based clinical practice guidelines are becoming increasingly important in physical therapy. For the purpose of meeting the goals of designing, implementing, and evaluating strategies to facilitate the development of more EBP in primary care physical therapy, a valid and reliable questionnaire for measuring attitudes, knowledge, behavior, prerequisites, and barriers related to EBP and guidelines is needed. less thanbrgreater than less thanbrgreater thanObjective. The 3 objectives of this study were: (1) to translate and cross-culturally adapt a questionnaire to a Swedish primary care context for the purpose of measuring various aspects of EBP and guidelines in physical therapy, (2) to further develop the questionnaire to examine more aspects of guidelines, and (3) to test the validity and reliability of the adapted Swedish questionnaire. less thanbrgreater than less thanbrgreater thanDesign. This was an instrument development study with validity and reliability testing. less thanbrgreater than less thanbrgreater thanMethods. A previously used questionnaire about EBP was translated and cross-culturally adapted to a Swedish primary care physical therapy context. Additional items were constructed. A draft version was pilot tested for content validity (n=10), and a revised version was tested for test-retest reliability (n=42). The percentage of agreement between the 2 tests was analyzed. less thanbrgreater than less thanbrgreater thanResults. The development process resulted in a first questionnaire draft containing 48 items. The validation process resulted in a second draft with acceptable content validity and consisting of 38 items. The test-retest analysis showed that the median percentage of agreement was 67% (range=41%-81%). After removal or revision of items with poor agreement, the final questionnaire included 31 items. less thanbrgreater than less thanbrgreater thanLimitations. Only face validity and content validity were tested. less thanbrgreater than less thanbrgreater thanConclusions. The final translated and adapted questionnaire was determined to have good face and content validity and acceptable reliability for measuring self-reported attitudes, knowledge, behavior, prerequisites, and barriers related to EBP and guidelines among physical therapists in primary care settings.

    Place, publisher, year, edition, pages
    American Physical Therapy Association (APTA), 2013
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-95503 (URN)10.2522/ptj.20120270 (DOI)000319546800010 ()
    Available from: 2013-07-05 Created: 2013-07-05 Last updated: 2015-11-09
    2. Determinants of Guideline Use in Primary Care Physical Therapy: A Cross-Sectional Survey of Attitudes, Knowledge, and Behavior
    Open this publication in new window or tab >>Determinants of Guideline Use in Primary Care Physical Therapy: A Cross-Sectional Survey of Attitudes, Knowledge, and Behavior
    Show others...
    2014 (English)In: Physical Therapy, ISSN 0031-9023, E-ISSN 1538-6724, Vol. 94, no 3, 343-354 p.Article in journal (Refereed) Published
    Abstract [en]

    Background. Understanding of attitudes, knowledge, and behavior related to evidence-based practice (ESP) and use of evidence-based clinical practice guidelines in primary care physical therapy is limited. Objectives. The objectives of this study were: (1) to investigate self-reported attitudes, knowledge, behavior, prerequisites, and barriers related to EBP and guideline use among physical therapists in primary care and (2) to explore associations of self-reported use of guidelines with these social cognitive factors along with demographic and workplace characteristics. Design. This was a cross-sectional survey. Methods. A web-based survey of 419 physical therapists in primary care in western Sweden was performed. Multiple logistic regression analysis was performed to examine factors associated with guideline use. Results. The response rate was 64.7%. Most respondents had positive attitudes toward EBP and guidelines: 90% considered EBP necessary, and 96% considered guidelines important. Approximately two thirds reported confidence in finding and using evidence. One third reported being aware of guidelines. Thirteen percent knew where to find guidelines, and only 9% reported having easy access to guidelines. Fewer than half reported using guidelines frequently. The most important barriers to using guidelines were lack of time, poor availability, and limited access to guidelines. Young age and brief work experience were associated with positive attitudes toward EBP. A postgraduate degree was associated with higher application of EBP. Positive attitudes, awareness of guidelines, considering guidelines to facilitate practice, and knowing how to integrate patient preferences with guideline use were associated with frequent use of guidelines. Limitations. Data were self-reported, which may have increased the risk of social.desirability bias. Conclusions. Use of guidelines was not as frequent as could be expected in view of the positive attitudes toward EBP and guidelines among physical therapists. Awareness of and perceived access to guidelines were limited. The identified determinants can be addressed when developing guideline implementation strategies.

    Place, publisher, year, edition, pages
    American Physical Therapy Association (APTA), 2014
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-106033 (URN)10.2522/ptj.20130147 (DOI)000332351300008 ()
    Available from: 2014-04-17 Created: 2014-04-17 Last updated: 2015-11-09
    3. Evaluation of a tailored, multi-component intervention for implementation of evidence-based clinical practice guidelines in primary care physical therapy: a non-randomized controlled trial.
    Open this publication in new window or tab >>Evaluation of a tailored, multi-component intervention for implementation of evidence-based clinical practice guidelines in primary care physical therapy: a non-randomized controlled trial.
    Show others...
    2014 (English)In: BMC Health Services Research, ISSN 1472-6963, Vol. 14, no 1, 105- p.Article in journal (Refereed) Published
    Abstract [en]

    BACKGROUND:

    Clinical practice guidelines are important for transmitting research findings into practice and facilitating the application of evidence-based practice (EBP). There is a paucity of knowledge about the impact of guideline implementation strategies in primary care physical therapy. The aim of this study was to evaluate the effect of a guideline implementation intervention in primary care physical therapy in western Sweden.

    METHODS:

    An implementation strategy based on theory and current evidence was developed. A tailored, multi-component implementation intervention, addressing earlier identified determinants, was carried out in three areas comprising 28 physical therapy practices including 277 physical therapists (PTs) (intervention group). In two adjacent areas, 171 PTs at 32 practices received no intervention (control group). The core component of the intervention was an implementation seminar with group discussions. Among other components were a website and email reminders. Data were collected at baseline and follow-up with a web-based questionnaire. Primary outcomes were the self-reported awareness of, knowledge of, access to, and use of guidelines. Secondary outcomes were self-reported attitudes toward EBP and guidelines. Analyses were performed using Pearson's χ2 test and approximative z-test.

    RESULTS:

    168 PTs (60.6%) in the intervention group and 88 PTs (51.5%) in the control group responded to the follow-up questionnaire. 186/277 PTs (67.1%) participated in the implementation seminars, of which 97 (52.2%) responded. The proportions of PTs reporting awareness of (absolute difference in change 20.6%, p = 0.023), knowledge where to find (20.4%, p = 0.007), access to (21.7%, p < 0.001), and frequent use of (9.5%, NS) guidelines increased more in the intervention group than in the control group. The proportion of PTs reporting frequent guideline use after participation in the implementation seminar was 15.2% (p = 0.043) higher than the proportion in the control group. A higher proportion considered EBP helpful in decision making (p = 0.018). There were no other significant differences in secondary outcomes.

    CONCLUSIONS:

    A tailored, theory- and evidence-informed, multi-component intervention for the implementation of clinical practice guidelines had a modest, positive effect on awareness of, knowledge of, access to, and use of guidelines, among PTs in primary care in western Sweden. In general, attitudes to EBP and guidelines were not affected.

    Place, publisher, year, edition, pages
    BioMed Central, 2014
    Keyword
    Implementation; Physical therapy; Evidence-based practice; Practice guidelines
    National Category
    Physiotherapy
    Identifiers
    urn:nbn:se:liu:diva-105610 (URN)10.1186/1472-6963-14-105 (DOI)000333535400002 ()24589291 (PubMedID)
    Available from: 2014-03-28 Created: 2014-03-28 Last updated: 2015-11-09
    4. Clinical practice in line with evidence?: A survey among primary care physiotherapists in western Sweden
    Open this publication in new window or tab >>Clinical practice in line with evidence?: A survey among primary care physiotherapists in western Sweden
    Show others...
    2015 (English)In: Journal of Evaluation In Clinical Practice, ISSN 1356-1294, E-ISSN 1365-2753, Vol. 21, no 6, 1169-1177 p.Article in journal (Refereed) Published
    Abstract [en]

    Rationale, aims and objectives

    Evidence-based practice is becoming increasingly important in primary care physiotherapy. Clinical practice needs to reflect current best evidence and be concordant with evidence-based clinical guidelines. There is limited knowledge about therapeutic interventions used in primary care physiotherapy in Sweden. The objectives were to examine preferred treatment interventions reported by publicly employed physiotherapists in primary care for three common musculoskeletal disorders (low back pain, neck pain and subacromial pain), the extent to which these interventions were supported by evidence, and associations with demographic variables.

    Methods

    419 physiotherapists in primary care in western Sweden were surveyed using a validated web-based questionnaire.

    Results

    The survey was completed by 271 respondents (65%). Median number of interventions reported was 7 (range 1–16). The most common treatment interventions across the three conditions were advice on posture (reported by 82–94%), advice to stay active (86–92%), and different types of exercise (65–92%). Most of these interventions were supported by evidence. However, interventions with insufficient evidence, such as advice on posture, TENS and aquatic exercise, were also used by 29–96%. Modalities such as laser therapy and ultrasound were sparingly used (<5%), which is in line with evidence. For neck pain, use of evidence-based interventions was associated with gender and for subacromial pain, with work experience.

    Conclusions

    Advice and exercise therapy were the interventions most frequently reported across the three diagnoses, illustrating an active treatment strategy. While most reported interventions are supported by evidence, interventions with unclear or no evidence of effect were also used to a high extent.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2015
    Keyword
    clinical practice, evidence, evidence-based practice, interventions, physical therapy, treatment
    National Category
    Health Care Service and Management, Health Policy and Services and Health Economy Family Medicine
    Identifiers
    urn:nbn:se:liu:diva-122555 (URN)10.1111/jep.12380 (DOI)000371414500032 ()25988993 (PubMedID)
    Note

    Funding agencies: local Research and Development Board for Gothenburg and Sodra Bohuslan; Linkoping University

    Available from: 2015-11-09 Created: 2015-11-09 Last updated: 2016-07-14Bibliographically approved
    5. “In the physio we trust”: A qualitative study on patients’ preferences for physiotherapy
    Open this publication in new window or tab >>“In the physio we trust”: A qualitative study on patients’ preferences for physiotherapy
    2017 (English)In: Physiotherapy Theory and Practice, ISSN 0959-3985, E-ISSN 1532-5040, Vol. 33, no 7, 535-549 p.Article in journal (Refereed) Published
    Abstract [en]

    Background: Patient preferences are suggested to be incorporated in clinical decision making, but little is known about preferences for physiotherapy treatment of patients with musculoskeletal pain. This study aimed to explore preferences regarding physiotherapy treatment and participation in decision making, of patients who seek primary care physiotherapy for pain in the back, neck or shoulder.

    Methods: A qualitative study set in an urban physiotherapy clinic in Sweden. Individual, semi-structured interviews were conducted with a purposeful sample of 20 individuals who sought physiotherapy for back, neck or shoulder pain. The interviews were digitally recorded, transcribed verbatim and analysed with qualitative content analysis.

    Results: An overarching theme, embracing six categories, was conceptualised: Trust in the physiotherapist fosters active engagement in therapy. Most informants preferred active treatment strategies such as exercise and advice for self-management, allowing them to actively engage in their therapy. Some preferred passive treatments, primarily acupuncture (because they had heard that it works well) or massage therapy (because “it feels good”). Preferences were consistent across the three musculoskeletal conditions. Key influencers on treatment preferences were previous experiences and media. All informants wanted to be involved in the clinical decision making, but to varying extents. Some expressed a preference for an active role and wanting to share decisions while others were content with a passive role. Expectations for a professional management were reflected in trust and confidence in physiotherapists’ skills and competence, expectations for good outcomes, and believing that treatment methods should be evidence-based.

    Conclusions: Trust in the physiotherapist’s ability to choose appropriate treatment and confidence in the professional skills and competence of physiotherapists, as well as a desire to participate in clinical decision making, fostered active engagement in physiotherapy. Preferences for particular interventions were subordinate, although a preference for active treatments dominated. Preferences for active engagement need to be embraced by the physiotherapist. Awareness of these preferences can facilitate clinical decision making and contribute to increased quality of care for patients with musculoskeletal pain.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2017
    Keyword
    Physical therapy, patient preferences, shared decision making, primary care, guidelines
    National Category
    Physiotherapy Public Health, Global Health, Social Medicine and Epidemiology
    Identifiers
    urn:nbn:se:liu:diva-122556 (URN)10.1080/09593985.2017.1328720 (DOI)000403937700003 ()
    Note

    Funding agencies: Local Research and Development Board for Gothenburg; Local Research and Development Board for Sodra Bohuslan

    Previous status of this publication was Manuscript

    Available from: 2015-11-09 Created: 2015-11-09 Last updated: 2017-07-07Bibliographically approved
  • 46.
    Jansson, Joel
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Ambient Occlusion for Dynamic Objects and Procedural Environments2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In computer graphics, lighting is an important area. To simulate shadows from area light sources, indirect lighting and shadows from indirect light, a class of algorithms commonly known as global illumination algorithms can be used. Ambient occlusion is an approximation to global illumination that can emulate shadows from area light sources and shadows from indirect light, giving very soft shadows. For real-time applications, ambient occlusion can be precomputed and stored in maps or per vertex. However, that can only be done with good results if the geometry is static. Therefore, a number of methods that can handle more or less dynamic scenes have been introduced in the recent years.

    In this thesis, a collection of ambient occlusion methods for dynamic objects and procedural environments will be described. The main contribution is the introduction of a novel method that handles ambient occlusion for procedural environments. Another contribution is a description of an implementation of Screen Space Ambient Occlusion (SSAO).

    SSAO is an algorithm that calculates approximate ambient occlusion in real-time by using the depths of surrounding pixels. It handles completely dynamic scenes with good performance.

    The method for procedural environments handles the scenario where a number of building blocks are procedurally assembled at run-time. The idea is to precompute an ambient occlusion map for each building block where the self-occlusion is stored. In addition, an ambient occlusion grid is precomputed for each block to accommodate the inter-block occlusion. At run-time, after the building blocks have been assembled, the ambient occlusion from the grids is blended with the ambient occlusion from the maps to generate new maps, valid for the procedural environment. Following that, the environment can be rendered with high quality ambient occlusion at almost no cost, in the same fashion as for a static environment where the ambient occlusion maps can be completely precomputed.

  • 47.
    Mensmann, Jörg
    et al.
    University of Münster, Germany.
    Ropinski,, Timo
    University of Münster, Germany.
    Hinrichs, Klaus
    University of Münster, Germany.
    An Advanced Volume Raycasting Technique using GPU Stream Processing2010In: Computer Graphics Theory and Applications, GRAPP 2010, 2010, 190-198 p.Conference paper (Other academic)
    Abstract [en]

    GPU-based raycasting is the state-of-the-art rendering technique for interactive volume visualization. The ray traversal is usually implemented in a fragment shader, utilizing the hardware in a way that was not originally intended. New programming interfaces for stream processing, such as CUDA, support a more general programming model and the use of additional device features, which are not accessible through traditional shader programming. In this paper we propose a slab-based raycasting technique that is modeled specifically to use these features to accelerate volume rendering. This technique is based on experience gained from comparing fragment shader implementations of basic raycasting to implementations directly translated to CUDA kernels. The comparison covers direct volume rendering with a variety of optional features, e.g., gradient and lighting calculations. Our findings are supported by benchmarks of typical volume visualization scenarios. We conclude that new stream processing models can only gain a small performance advantage when directly porting the basic raycasting algorithm. However, they can be advantageous through novel acceleration methods which use the hardware features not available to shader implementations.

  • 48.
    Hammarström, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Ali, Malik M
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Mishra, Rajesh
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Salagic, Belma
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Svensson, Samuel
    AstraZeneca RandD.
    Tengvall, Pentti
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    An Auto-Catalytic Surface for Conformational Replication of Amyloid Fibrils-Genesis of an Amyloid World?2011In: Origins of life and evolution of the biosphere, ISSN 0169-6149, E-ISSN 1573-0875, Vol. 41, no 4, 373-383 p.Article in journal (Refereed)
    Abstract [en]

    Amyloid fibrils are composed of self assembled stacked peptide or protein molecules folded and trapped in a stable cross-beta-sheet conformation. The amyloid fibrillation mechanism represents an intriguing self-catalyzed process rendering replication of a molecular conformational memory of interest for prebiotic chemistry. Herein we describe how a solid surface can be rendered auto-catalytic for fibrillation of a protein solution. We have discovered that a hydrophobic silicon or glass surface can be made to continuously fibrillate solutions of insulin monomers under stressed conditions (pH 1.6, 65 degrees C). It was found that the surface acts as a platform for the formation of nascent seeds that induce fibril replication on and at the surface. This autocatalytic effect stems from a layer a few insulin molecules thick representing an oligomeric layer of misfolded, conformationally trapped, insulin molecules that rapidly through epitaxial growth catalyze the rate determining step (nucleation) during fibril replication. This autocatalytic layer is generated by the protein-solid surface interaction and conformational changes of the adsorbed protein during exposure at the air-water interface. The resulting autocatalytic surface thus both initiates local conformational molecular self-replication and acts as a reservoir for fibril seeds budding off into solution spreading fibril replication entities to the surrounding medium. The possibility of catalysis of the conformational replication process by minute amounts of nucleation sites located on a recruiting surface can evade the issue of dramatic concentration dependence of amyloidogenesis.

  • 49.
    Eriksson, Oskar
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Rydkvist, Emil
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    An in-depth analysis of dynamically rendered vector-based maps with WebGL using Mapbox GL JS2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The regular way of displaying maps in a web browser is by downloading raster images from a server and lay them side by side to make up a map. If any information on the map is changed, new images has to be downloaded, it cannot be done on the client. The introduction of WebGL opens up a whole new world of delivering advanced graphics content to the end user in a web browser. Utilizing this technology for displaying maps means only the source data is sent to the web browser where the map gets rendered using the device's GPU. This adds a number of benefits such as the ability of changing map appearance on the client, add new features to the map and often less data transfer. It however sets higher expectations of the client device's hardware as it needs to render the map at a high enough frame rate to not appear slow and unresponsive. This thesis investigates a framework for client side map rendering in a web browser, Mapbox GL JS, with focus on performance. It shows how map source data can be generated as well as its corresponding style rules are constructed with performance in mind. It provides benchmarking results of different map data sets with different detail intensity and shows that a device with good GPU performance is needed for an acceptable user experience. It also shows that lowering the amount of rendered detail does not necessarily result in better performance.

  • 50.
    Shen, Li
    et al.
    Image and Pattern Analysis Laboratory, Department of Computer and Information Science, University of Massachusetts.
    Gaob, Ling
    Angiogenesis Research Center, Departments of Radiology and Cardiology, Dartmouth Medical School, Lebanon.
    Zhuang, Zhenwu
    Angiogenesis Research Center, Departments of Radiology and Cardiology, Dartmouth Medical School, Lebanon.
    De Muinck, Ebo
    Angiogenesis Research Center, Departments of Radiology and Cardiology, Dartmouth Medical School, Lebanon.
    Huang, Heng
    Dartmouth Experimental Visualization Laboratory, Department of Computer Science, Dartmouth College, Hanover.
    Makedon, Fillia
    Dartmouth Experimental Visualization Laboratory, Department of Computer Science, Dartmouth College, Hanover.
    Pearlman, Justin
    Angiogenesis Research Center, Departments of Radiology and Cardiology, Dartmouth Medical School, Lebanon.
    An interactive 3D visualization and manipulation tool foreffective assessment of angiogenesis and arteriogenesis usingcomputed tomographic angiography2005In: Progress in Biomedical Optics and Imaging, ISSN 1605-7422, Vol. 5744, no II, 848-858 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents IVM, an Interactive Vessel Manipulation tool that can help make effective and efficient assessment

    of angiogenesis and arteriogenesis in computed tomographic angiography (CTA) studies. IVM consists

    of three fundamental components: (1) a visualization component, (2) a tracing component, and (3) a measurement

    component. Given a user-specified threshold, IVM can create a 3D surface visualization based on it. Since

    vessels are thin and tubular structures, using standard isosurface extraction techniques usually cannot yield

    satisfactory reconstructions. Instead, IVM directly renders the surface of a derived binary 3D image. The image

    volumes collected in CTA studies often have a relatively high resolution. Thus, compared with more complicated

    vessel extraction and visualization techniques, rendering the binary image surface has the advantages of being

    effective, simple and fast. IVM employs a semi-automatic approach to determine the threshold: a user can adjust

    the threshold by checking the corresponding 3D surface reconstruction and make the choice. Typical tracing

    software often defines ROIs on 3D image volumes using three orthogonal views. The tracing component in IVM

    takes one step further: it can perform tracing not only on image slices but also in a 3D view. We observe that

    directly operating on a 3D view can help a tracer identify ROIs more easily. After setting a threshold and tracing

    an ROI, a user can use IVM’s measurement component to estimate the volume and other parameters of vessels

    in the ROI. The effectiveness of the IVM tool is demonstrated on rat vessel/bone images collected in a previous

    CTA study.

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