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  • 1. Ahmad, Tausif
    et al.
    Gooran, Sasan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Hybrid Color Halftoning2010Conference paper (Refereed)
  • 2.
    Bang, Magnus
    et al.
    Linköping University, Department of Computer and Information Science.
    Ragnemalm, Eva L.Linköping University, Department of Computer and Information Science.
    Persuasive Technology: Design for Health and Safety2012Conference proceedings (editor) (Refereed)
  • 3.
    Chien, Trinh Van
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, Faculty of Science & Engineering. Sungkyunkwan University, South Korea.
    Dinh, Khanh Quoc
    ungkyunkwan Univ, Sch Elect & Comp Engn, Seoul, South Korea.
    Jeon, Byeungwoo
    Sungkyunkwan Univ, Sch Elect & Comp Engn, Seoul, South Korea.
    Burger, Martin
    University of Munster, Germany.
    Block compressive sensing of image and video with nonlocal Lagrangian multiplier and patch-based sparse representation2017In: Signal processing. Image communication, ISSN 0923-5965, E-ISSN 1879-2677, Vol. 54, 93-106 p.Article in journal (Refereed)
    Abstract [en]

    Although block compressive sensing (BCS) makes it tractable to sense large-sized images and video, its recovery performance has yet to be significantly improved because its recovered images or video usually suffer from blurred edges, loss of details, and high-frequency oscillatory artifacts, especially at a low subrate. This paper addresses these problems by designing a modified total variation technique that employs multi-block gradient processing, a denoised Lagrangian multiplier, and patch-based sparse representation. In the case of video, the proposed recovery method is able to exploit both spatial and temporal similarities. Simulation results confirm the improved performance of the proposed method for compressive sensing of images and video in terms of both objective and subjective qualities.

    The full text will be freely available from 2019-03-02 14:23
  • 4.
    Eilertsen, Gabriel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Mantiuk, Rafal
    University of Cambridge.
    Unger, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Real-time noise-aware tone mapping2015In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, ISSN 0730-0301, Vol. 34, no 6, 198:1-198:15 p., 198Article in journal (Refereed)
    Abstract [en]

    Real-time high quality video tone mapping is needed for manyapplications, such as digital viewfinders in cameras, displayalgorithms which adapt to ambient light, in-camera processing,rendering engines for video games and video post-processing. We propose a viable solution for these applications by designing a videotone-mapping operator that controls the visibility of the noise,adapts to display and viewing environment, minimizes contrastdistortions, preserves or enhances image details, and can be run inreal-time on an incoming sequence without any preprocessing. To ourknowledge, no existing solution offers all these features. Our novelcontributions are: a fast procedure for computing local display-adaptivetone-curves which minimize contrast distortions, a fast method for detailenhancement free from ringing artifacts, and an integrated videotone-mapping solution combining all the above features.

  • 5.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Physical Model of the Slide Guitar: An Approach Based on Contact Forces2012In: Proceedings of Audio Engineering Society Convention 132, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper we approach the synthesis of the slide guitar, which is a particular play mode of the guitar where continuous tuning of the tones is achieved by sliding a metal orglass piece, the bottleneck, along thestrings on the guitar neck side. The bottleneck constitues a unilateral constraint for the string vibration.Dynamics is subject to friction, scraping, textured displacement and collisions. The presented model is physically inspired and is based on a dynamic model of friction, together with a geometrical model of the textured displacements and a model for collisions of the string with the bottlenck. These models are suitablefor implementation in a digital waveguide computational scheme for the 3D vibration of the string, where continuous pitch bending is achieved by allpass filters to approximate fractional delays, friction is captured by nonlinear state-space systems in the slide junction and textured displacements by signal injection at avariable point in the waveguide.

  • 6.
    Evangelista, Gianpaolo
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Physical Model of the String-Fret Interaction2011In: Proc. of Digital Audio Effect Conf., 2011, 345-351. p.Conference paper (Refereed)
    Abstract [en]

    In this paper, a model for the interaction of the strings with the frets in a guitar or other fretted string instruments is introduced. In the two-polarization representation of the string oscillations it is observed that the string interacts with the fret in different ways. While the vertical oscillation is governed by perfect or imperfect clamping of the string on the fret, the horizontal oscillation is subject to friction of the string over the surface of the fret. The proposed model allows, in particular, for the accurate evaluation of the elongation of the string in the two modes, which gives rise to audible dynamic detuning. The realization of this model into a structurally passive system for use in digital waveguide synthesis is detailed. By changing the friction parameters, the model can be employed in fretless instruments too, where the string directly interacts with the neck surface.

  • 7.
    Evangelista, Gianpaolo
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Smith III, Julius Orion
    CCRMA, Stanford University, California, USA.
    Structurally Passive Scattering Element for Modeling Guitar Pluck Action2010In: Proc. of Digital Audio Effect Conf., Graz, Austria, 2010, 10-17 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we propose new models for the plucking interaction of the player with the string for use with digital waveguide simulation of guitar. Unlike the previously presented models, the new models are based on structurally passive scattering junctions,which have the main advantage of being properly scaled for use infixed-point waveguide implementations and of guaranteeing stability independently of the plucking excitation. In a first model we start from the Cuzzucoli-Lombardo equa-tions [1], within the Evangelista-Eckerholm [2] propagation formulation, in order to derive the passive scattering junction by means of bilinear transformation. In a second model we start from equations properly modeling the finger compliance by means of a spring. In a third model we formalize the interaction in terms ofdriving impedances. The model is also extended using nonlinear (feathering) compliance models.

  • 8.
    Flinke, Johan
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Utvärdering och testning av ett bildbehandlingsprogram för volymberäkning av mat i nutritionsforskning2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Vid ett forskningsarbete som bedrivs om barnfetma finns det ett intresse av att säkerställa den mängd mat som deltagarna konsumerar. För att komma runt problematiken med felbedömningar kring det faktiska födointaget har det tagits fram ett program som med hjälp av stereoskopisk bildbehandling ska kunna göra volymberäkningar baserade på fotografier av deltagarnas måltider. På så sätt elimineras den felmarginal som den mänskliga faktorn kan stå för genom att låta en dator ta fram den exakta mängden föda som konsumerats och det ger även en ökad möjlighet att lagra den insamlade datamängden för framtida studier.

    Det här arbetet syftar till att evaluera programmet FoodIQ som tagits fram speciellt för detta ändamål. Även om programmet har levererats och tagits i bruk, så har det ännu inte gjorts några omfattande tester som kan verifiera att programmet klarar av att mäta volymer korrekt. Huvuddelen av det här arbetet har bestått i att genomföra ett stort antal volymberäkningar för att på så sätt kunna få en uppfattning om programmets grad av noggrannhet.

    De slutsatser som kunde dras var att även om programmet visar upp en stor potential så lider det av några allvarliga brister som gör att det i dagsläget inte fungerar som det är tänkt. I den här rapporten kommer det att redogöras en del kring programmets användarvänlighet samt funktionalitet . Det kommer även att presenteras resultatet av de tester som genomfördes där syftet var att försöka ta reda på vilka faktorer som avgör huruvida en volymmätning fungerar som det är tänkt eller inte.   

  • 9.
    Fritz, Jenny
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Utveckling av ett verktyg för produktkataloggenerering2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Today, product catalogs are published and distributed by a large share of retail companies.However, the process of catalog production can be both time consuming and resource heavy.The purpose of this thesis has been to find a solution to that problem. This was done byresearching different needs and demands regarding catalog production which was then followedby implementation of a software tool that could accomodate those needs. The goal was toautomatically produce a product catalog in PDF format out of an existing product database.A pilot study showed that despite differences in existing catalog layouts, there still aresome common elements such as product image and price. This was used as a basis during theimplementation in which it was assumed that a product database, no matter the type of datasource, always contains specific information elements to be published. To allow for differentlayouts of a product catalog, a separate template handler was implemented. The purposeof this was to give the user an opportunity to configure for instance text field placements,image dimensions and which background images to use - all in favor of individual needs andoppinions.To reach the goals the scope of the project was extended and during spring 2013 it wasfinalized with the desired functionalities. Despite this, a whole lot of possibilities regardingfurther development can be seen, especially since the need of a more efficient process of catalogproduction seems to exist.

  • 10.
    Glansberg, Sven
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, The Institute of Technology.
    Presentation av reservdelskatalog med modellbaserat konstruktionsunderlag: En fallstudie av Saabs konceptutveckling för teknikinformation till stridsflygplanet Gripen NG2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the military aerospace industry, product data management in the product lifecycle, and development of logistics support are key areas that affect management of requirements and costs. The most recent strategy for these challenges is model-based definition (MBD). The discipline of technical communication has yet to explore and exploit the potential of MBD. Expected benefits include better ways of presenting illustrations and more efficient methodologies for production.

    This problem was investigated through a case study of the concept development of technical communication for Saab's fighter aircraft Gripen NG. The study focused on the illustrated parts catalog and its use. This work contributes with a model that describes four design levels for information systems, where presentation is the one in focus. In addition, comparable practices for management of MBD data were investigated in the case.

    The study found that the technical communication department is facing a transition from document-based management to development of information systems. Furthermore, three proposals for the next generation of parts catalogs are discussed. Two conclusions were reached. First, a lack of knowledge regarding the use of the parts catalog makes it difficult to assess new ways of presentation. And second, the improvements made in methodology and presentation in other MBD applications of the product life cycle are not immediately transferable to the parts catalog. Hence, suggestions for future research and work are presented.

  • 11.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Context Dependent Color Halftoning in Digital Printing2000In: IS&Ts PICS Conference 2000, The Society for Imaging Science and Technology , 2000, 242-246 p.Conference paper (Other academic)
  • 12.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Context Dependent Color Halftoning with Color Matching2001In: Proceedings of the Technical Association of the Graphic Arts, TAGA, 2001, Technical Association of the Graphic Arts , 2001, 304-317 p.Conference paper (Other academic)
  • 13.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Halftoning and Color Noise2001In: Ninth Color Imaging Conference: Color Science and Engineering: Systems, Technologies, and Applications, The Society for Imaging Science and Technology , 2001, 148-188 p.Conference paper (Other academic)
    Abstract [en]

    A frequency modulated color halftoning algorithm is presented in this paper.Unlike the normal approach of halftoning a color image,in which the color separations of the original image are halftoned independently,the original color image is halftoned in a context dependent manner.The strategy to reduce color noise and gain control over color gamut is to prevent dot-on-dot printing as much as possible. The color shifts that might occur because of this dot-off-dot printing strategy have to be compensated before halftoning. This transformation uses some data for the printer with which the halftoned color image is supposed to be printed. The experiments verify that the color noise is notably smaller in the images that are halftoned by the proposed method compared to the images halftoned using the normal approach of halftoning color images.The method also offers the possibility of treating the color separations of the original image differently if needed.For example,the yellow separation should be treated differently from the other separations, because the yellow dots are less visible than the other color dots when they are printed on a white paper.Two criteria for objectively measuring the quality of the produced results are also discussed.

  • 14.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Hybrid Halftoning in Flexography2003In: Proceedings of the Technical Association of the Graphic Arts, TAGA, Technical Association of the Graphic Arts , 2003Conference paper (Other academic)
  • 15.
    Gooran, Sasan
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Color Halftoning in Digital Printing1999Conference paper (Other academic)
  • 16.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    High-speed first- and second-order frequency modulated halftoning2015In: Journal of Electronic Imaging (JEI), ISSN 1017-9909, Vol. 24, no 2Article in journal (Refereed)
    Abstract [en]

    Halftoning is a crucial part of image reproduction in print. First-order FM halftones, in which the single dots are stochastically distributed, is widely used in printing technologies, such as inkjet, that are able to stably print isolated dispersed dots. Printers, such as laser printers, that utilize electrophotographic technology are not able to stably print the isolated dots and therefore use clustered-dot halftones. Periodic clustered-dot, i.e. AM, halftones are commonly used in this type of printers but they suffer from undesired periodic interference pattern called moiré. An alternative solution is to use second-order FM halftones in which the clustered dots are stochastically distributed. The iterative halftoning techniques, that usually result in well-formed halftones, are operating on the whole input image and require extensive computations and thereby are very slow when the input image is large. In this paper, we introduce a method to generate image independent threshold matrices for first and second-order FM halftoning. The first-order threshold matrix generates well-formed halftone patterns and the second-order FM threshold matrix can be adjusted to produce clustered-dots of different size, shape and alignment. Using predetermined and image independent threshold matrices makes the proposed halftoning method a point-by-point process and thereby very fast.

  • 17.
    Gooran, Sasan
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Near-optimal model-based halftoning technique with dot gain1998In: SPIE Volume 3308 - Very High Resolution and Quality Imaging III, SPIE - International Society for Optical Engineering, 1998Conference paper (Other academic)
    Abstract [en]

    We present a novel halftoning technique for transformation of continuous tone images into binary halftoned separations. The algorithm is based on a successive assessment of the near optimum sequence of positions to render. The impact of each rendered point is fed back to the process as a distribution function thereby influencing the following evaluations. The distribution function is not constant over the density range. In order to be able to separate the dots adequately in the highlights the 'width or radius' of the distribution has to be made larger than in the mid-tones. The human visual system and the effect of dot gain are also taken into account in this algorithm. The notion of incremental dot gain is introduced. Since the series of positions to render are not known in advance the final necessary dot gain compensation is impossible to assess. However the incremental dot gain can be computed in advance for each configuration of dots and taken into account in the process of generating the output. Some aspects of the process have certain resemblance with error distribution based algorithms. However the raster scanning sequence of rendering the output points in usual error diffusion algorithms is completely different from the image dependent traversal described in this paper.

  • 18.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Yang, Li
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Basics of tone reproduction2015In: Handbook of Digital Imaging / [ed] Michael Kriss, Wiley , 2015Chapter in book (Refereed)
    Abstract [en]

     There is no doubt that printing has been one of the most important technological inventions for

    human civilization. Books, magazines, news papers, and so on have been printed for different

    purposes such as distributing knowledge, thoughts, and news and commercializing products.

    Tone reproduction for images has been one of the challenging parts of the printing technology

    because the printing devices are restricted to a few color inks, whereas the original image

    may consist of millions of color tones. In this chapter, the basics of the tone reproduction

    are introduced. We begin with a brief history of halftoning and a short introduction of digitalization.

    It is followed by the description on visual acuity of human visual system and its

    relationship with the screen resolution. Then the basic and general concepts of tone reproduction,

    such as screen frequency, print resolution, screen angle and Moiré pattern, and dot gain

    are described and illustrated. Dot gain is only briefl y described and illustrated in this chapter as

    it is thoroughly discussed in Physical Evaluation of the Quality of Color Halftone . Finally,

    technologies for color reproduction and color halftoning are discussed.

  • 19.
    Gooran, Sasan
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yang, Li
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Frequency Modulated Halftoning and Dot Gain2004In: Proceedings of the Technical Association of the Graphic Arts, TAGA, Technical Association of the Graphic Arts , 2004Conference paper (Other academic)
  • 20.
    Gooran, Sasan
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Österberg, Mats
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Kruse, Björn
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Hybrid Halftoning: A novel Algorithm for Using Multiple Halftoning Technologies1996Conference paper (Refereed)
    Abstract [en]

    The rendering quality in halftoning is a critical issue. The quality aspects are more important in some images than in others. The quality of skin tone rendering of halftoned images generated by frequency modulated (FM) halftoning techniques differs from those generated by conventional halftoning techniques. Some judge the conventional halftoning techniques as superior in smoothly varying tones whereas frequency modulated halftoning techniques excel in heavily textured images. This paper describes an algorithm that can incorporate both technologies simultaneously. The technique is an iterative optimization of the binary halftone image with respect to the differences between the original and the halftoned images. The performance of the algorithm can be controlled by the nature of the original state of the iteration. The algorithm can in effect accommodate any type of halftone that can be described by a threshold matrix.

  • 21.
    Guo, Jun
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Further development of shaders for realistic materials and global illumination effects2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Shader programming is important for realistic material and global illumination real-time rendering, especially in 3D industrial fields nowadays, more and more customers of Visual Components Oy, a Finnish 3D software company have been found to be no longer only content with the correct simulation result, but also the result of realistic real-time rendering. This thesis project will provide a deep research on real world material classification, property definition and global illumination techniques in industrial fields. On the other hand, the Shader program for different materials and global illumination techniques are also created according to the classification and definition in this thesis work. Moreover, an external rendering tool Redway3D is evaluated as the reference and regarded as the considerable solution in the future development work.

  • 22.
    Gustafsson Coppel, Ludovic
    et al.
    Gjøvik University College, Norway.
    Le Moan, Steven
    Technical University of Darmstadt, Germany.
    Zitinski Elias, Paula
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Slavuj, Radovan
    Gjøvik University College, Norway.
    Hardeberg, Jon Yngve
    Gjøvik University College, Norway.
    Next generation printing - Towards spectral proofing2014Conference paper (Other academic)
  • 23.
    Günther, David
    et al.
    Saarbrücken, Germany.
    Reininghaus, Jan
    Zuse Institute Berlin, Germany.
    Wagner, Huber
    Lojasiewicza 6, Krakow, Poland .
    Hotz, Ingrid
    Zuse Institute Berlin, Germany.
    Efficient Computation of 3D Morse-Smale Complexes and Persistent Homology using Discrete Morse Theory2012In: The Visual Computer, ISSN 0178-2789, E-ISSN 1432-2315, Vol. 28, no 10, 959-969 p.Article in journal (Refereed)
    Abstract [en]

    We propose an efficient algorithm that computes the Morse–Smale complex for 3D gray-scale images. This complex allows for an efficient computation of persistent homology since it is, in general, much smaller than the input data but still contains all necessary information. Our method improves a recently proposed algorithm to extract the Morse–Smale complex in terms of memory consumption and running time. It also allows for a parallel computation of the complex. The computational complexity of the Morse–Smale complex extraction solely depends on the topological complexity of the input data. The persistence is then computed using the Morse–Smale complex by applying an existing algorithm with a good practical running time. We demonstrate that our method allows for the computation of persistent homology for large data on commodity hardware.

  • 24.
    Haake, Magnus
    et al.
    Department of Design Sciences, LTH, Lund University, Lund, Swede.
    Gulz, Agneta
    LUCS (Div. of Cognitive Science), Lund University, Kungshuset, Lundagård, Lund, Sweden.
    Visual Stereotypes and Virtual Pedagogical Agents2008In: Journal of Educational Technology & Society, ISSN 1176-3647, E-ISSN 1436-4522, Vol. 11, no 4, 1-15 p.Article in journal (Refereed)
    Abstract [en]

    The paper deals with the use of visual stereotypes in virtual pedagogical agents and its potential impact in digital learning environments. An analysis of the concept of visual stereotypes is followed by a discussion of affordances and drawbacks as to their use in the context of traditional media. Next, the paper explores whether virtual pedagogical characters introduce anything novel with regard to the use of visual stereotypes - as compared both to real life interaction between humans and to the use of visual stereotypes in traditional non-interactive media such as magazines, film, television and video. It is proposed that novel affordances, as well as novel drawbacks, indeed are being introduced with the use of visual stereotypes in virtual characters. The conclusion of the paper is that knowledge on these matters can be useful both for developers of educational systems and for educators in enabling them to strengthen some pedagogical settings and activities.

  • 25.
    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.

  • 26.
    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.

  • 27.
    Hagen, Hans
    et al.
    University of Kaiserslautern.
    Hotz, Ingrid
    University of Kaiserslautern.
    Variational modeling methods for Visualization2004In: Visualization Handbook / [ed] Charles D. Hansen and Chris R. Johnson, Springer, 2004, 381-392 p.Chapter in book (Refereed)
    Abstract [en]

    Publisher Summary Variational modeling techniques are powerful tools for free-form modeling in CAD/CAM applications. Some of the basic principles are carrying over to scientific visualization. Others have to be modified and some totally new methods have been developed over the past couple of years. This chapter gives an extended survey of this area. Surfaces and solids designed in a computer graphics environment have many applications in modeling, animation, and visualization. The chapter concentrates on the visualization part. The chapter starts with the basics from differential geometry, which are essential for any variational method. Then, it surveys on variational surface modeling. The last step is the visualization part of geometric modeling. In this context, surface curves like geodesies and curvature lines play an important role. The corresponding differential equations are nonlinear, and in most cases numerical algorithms must be used. To be sure to visualize features at a high quality, algorithms with an inherent quality control are needed. The chapter presents the geometric algorithms, which satisfy this demand.

  • 28.
    Hauck, Shahram
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A Networked Workflow for a Fully Automated CtP Calibration System2011In: Proc. International Circle of Educational Institutes for Graphic Arts (IC), 2011Conference paper (Other academic)
    Abstract [en]

    One of the most important targets on the graphic market is to realize standardization. The standardization defines the target value of solid Lab and dot gain in printing process. In addition the tolerance range of these two values will be described by standardization. The correct dot gain will be achieved during the measuring of the dot gain in printing process by the additional calculation of a correction curve well known as Print Characteristic Curve (PCC) [1]. The Raster Image Processor (RIP) needs the PCC for the imaging of printing plate with the correct tone value. In this paper we will propose a Networked Workflow (figure 1) with the Workflow Control System (or alternatively a MIS Management Information System). This Networked Workflow is necessary for the realization of a Fully Automated CtP Calibration System.

  • 29.
    Hauck, Shahram
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gooran, Sasan
    An alternative method to determinate register variation using colorimetry or densitometry tools2011In: Proceedings of the Technical Association of the Graphic Arts, TAGA, Technical Association of the Graphic Arts , 2011, 340-353 p.Conference paper (Other academic)
  • 30.
    Havsvik, Oskar
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Enhanced Full-body Motion Detection for Web Based Games using WebGL2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    By applying the image processing algorithms used in surveillance systems on video data obtained from a web camera, a motion detection application can be created and incorporated into web based games. The use of motion detection opens up a vast field of new possibilities in game design and this thesis will therefore cover how to create a motion detection JavaScript module which can be used in web based games.

    The performance and quality of the motion detection algorithms are important to consider when creating an application. What motion detection algorithms can be used to give a qualitativerepresentation without affecting the performance of a web based game will be analyzed and implemented in this thesis. Since the performance of the Central Processing Unit will not suffice, WebGL and the parallelism of the Graphical Processing Unit will be utilized to implement some of the most recognized image processing algorithms used in motion detection systems. The work resulted in an application where Gaussian blur and Frame Subtraction were used to detect and return areas where motion has been detected.

  • 31.
    Johansson Fernstad, Sara
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Johansson, Jimmy
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A Task Based Performance Evaluation of Visualization Approaches for Categorical Data Analysis.2011In: Proceedings - 15th International Conferenceon Information Visualisation, Los Alamitos, CA, USA: IEEE Computer Society, 2011, 80-89 p.Conference paper (Other academic)
    Abstract [en]

    Categorical data is common within many areas and efficient methods for analysis are needed. It is, however, often difficult to analyse categorical data since no general measure of similarity exists. One approach is to represent the categories with numerical values (quantification) prior to visualization using methods for numerical data. Another is to use visual representations specifically designed for categorical data. Although commonly used, very little guidance is available as to which method may be most useful for different analysis tasks. This paper presents an evaluation comparing the performance of employing quantification prior to visualization and visualization using a method designed for categorical data. It also provides a guidance as to which visualization approach is most useful in the context of two basic data analysis tasks: one related to similarity structures and one related to category frequency. The results strongly indicate that the quantification approach is most efficient for the similarity related task, whereas the visual representation designed for categorical data is most efficient for the task related to category frequency.

  • 32.
    Johansson Fernstad, Sara
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Johansson, Jimmy
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Adams, Suzi
    Unilever Discover Port Sunlight, UK.
    Shaw, Jane
    Unilever Discover Port Sunlight, UK.
    Taylor, David
    Unilever Discover Port Sunlight, UK.
    Visual Exploration of Microbial Populations2011In: IEEE Symposium on Biological Data Visualization, 2011, 127-134 p.Conference paper (Other academic)
    Abstract [en]

    Studies of the ecology of microbial populations are increasingly common within many research areas as the field of microbiomics develops rapidly. The study of the ecology in sampled microbial populations generates high dimensional data sets. Although many analysis methods are available for examination of such data, a tailored tool was required to fulfill the need of interactivity and flexibility for microbiologists. In this paper, MicrobiVis is presented. It is a tool for visual exploration and interactive analysis of microbiomic populations. MicrobiVis has been designed in close collaboration with end users. It extends previous interactive systems for explorative dimensionality reduction by including a range of domain relevant features. It contributes a flexible and explorative dimensionality reduction as well as a visual and interactive environment for examination of data subsets. By combining information visualization and methods based on analytic tasks common in microbiology as a means for gaining new and relevant insights. The utility of MicrobiVis is demonstrated through a use case describinghow a microbiologist may use the system for a visual analysis of amicrobial data set. Its usability and potential is indicated throughpositive feedback from the current end users.

  • 33.
    Johansson, Sara
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Visual Exploration of Categorical and Mixed Data Sets2009In: Proceeding VAKD '09 Proceedings of the ACM SIGKDD Workshop on Visual Analytics and Knowledge Discovery: Integrating Automated Analysis with Interactive Exploration: Workshop on Visual Analytics and Knowledge Discovery, New York, USA: ACM Press, 2009, 21-29 p.Conference paper (Refereed)
    Abstract [en]

    For categorical data there does not exist any similarity measurewhich is as straight forward and general as the numericaldistance between numerical items. Due to this it is often difficultto analyse data sets including categorical variables or a combination of categorical and numerical variables (mixeddata sets). Quantification of categorical variables enablesanalysis using commonly used visual representations andanalysis techniques for numerical data. This paper presents a tool for exploratory analysis of categorical and mixed data, which uses a quantification process introduced in [Johansson2008]. The application enables analysis of mixed data sets by providingan environment for exploratory analysis using commonvisual representations in multiple coordinated views and algorithmic analysis that facilitates detection of potentially interesting patterns within combinations of categorical and numerical variables. The effectiveness of the quantificationprocess and of the features of the application is demonstratedthrough a case scenario.

  • 34.
    Johansson, Sara
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Jern, Mikael
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Johansson, Jimmy
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Interactive Quantification of Categorical Variables in Mixed Data Sets2008In: Information Visualisation, 2008. IV '08. 12th International Conference / [ed] Ebad Banissi, Liz Stuart, Mikael Jern, Gennady Andrienko, Francis T. Marchese, Nasrullah Memon, Reda Alhajj, Theodor G Wyeld, Remo Aslak Burkhard, Georges Grinstein, Dennis Groth, Anna Ursyn, Carsten Maple, Anthony Faiola and Brock Craft, Los Alamitos, California: IEEE Computer Society, 2008, 3-10 p.Conference paper (Refereed)
    Abstract [en]

    Data sets containing a combination of categorical and continuous variables (mixed data sets) are difficult to analyse since no generalized similarity measure exists for categorical variables. Quantification of categorical variables makes it possible to represent this type of data using techniques designed for numerical data. This paper presents a quantification process of categorical variables in mixed data sets that incorporates information on relationships among the continuous variables into the process, as well as utilizing the domain knowledge of a user. An interactive visualization environment using parallel coordinates as a visual interface is provided, where the user is able to control the quantification process and analyse the result. The efficiency of the approach is demonstrated using two mixed data sets.

  • 35.
    Johansson, Sara
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Johansson, Jimmy
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Interactive Dimensionality Reduction Through User-defined Combinations of Quality Metrics2009In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 15, no 6, 993-1000 p.Article in journal (Refereed)
    Abstract [en]

    Multivariate data sets including hundreds of variables are increasingly common in many application areas. Most multivariate visualization techniques are unable to display such data effectively, and a common approach is to employ dimensionality reduction prior to visualization. Most existing dimensionality reduction systems focus on preserving one or a few significant structures in data. For many analysis tasks, however, several types of structures can be of high significance and the importance of a certain structure compared to the importance of another is often task-dependent. This paper introduces a system for dimensionality reduction by combining user-defined quality metrics using weight functions to preserve as many important structures as possible. The system aims at effective visualization and exploration of structures within large multivariate data sets and provides enhancement of diverse structures by supplying a range of automatic variable orderings. Furthermore it enables a quality-guided reduction of variables through an interactive display facilitating investigation of trade-offs between loss of structure and the number of variables to keep. The generality and interactivity of the system is demonstrated through a case scenario.

  • 36.
    Johansson, Sara
    et al.
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Johansson, Jimmy
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology.
    Visual Analysis of Mixed Data Sets Using Interactive Quantification2009In: ACM SIGKDD Explorations Newsletter, ISSN 1931-0145, Vol. 11, no 2, 29-38 p.Article in journal (Refereed)
    Abstract [en]

    It is often diffcult to analyse data sets including a combi-nation of categorical and numerical variables (mixed datasets) since there does not exist any similarity measure whichis as straight forward and general as the numerical distancebetween numerical items. Quantication of categorical vari-ables enables analysis using commonly used visual represen-tations and analysis techniques for numerical data. Thispaper presents a tool for exploratory analysis of categoricaland mixed data which uses a quantication process intro-duced in [Johansson2008]. The application enables analysis of mixeddata sets by providing an environment for exploratory anal-ysis using common visual representations in multiple coordi-nated views and algorithmic analysis that facilitates detec-tion of potentially interesting patterns within combinationsof categorical and numerical variables. The generality andusefulness of the quantication process and of the featuresof the application is demonstrated through a case scenariousing a data set from the IEEE VAST 2008 Challenge.

  • 37.
    Johansson-Evegård, Erik
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Artist Friendly Fracture Modelling2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Destruction is one of the key aspects of visual effects. This report describes the work that was done to create a production ready pre-fracture modelling plug-in for Maya. It provides information on what methods that can be used to create a robust plug-in and various techniques for sampling points to create interesting fracture patterns using the Voronoi diagram. It also discusses how this work can be further built on to create an even better plug-in.

  • 38.
    Jönsson, Daniel
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Enhancing Salient Features in Volumetric Data Using Illumination and Transfer Functions2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The visualization of volume data is a fundamental component in the medical domain. Volume data is used in the clinical work-flow to diagnose patients and is therefore of uttermost importance. The amount of data is rapidly increasing as sensors, such as computed tomography scanners, become capable of measuring more details and gathering more data over time. Unfortunately, the increasing amount of data makes it computationally challenging to interactively apply high quality methods to increase shape and depth perception. Furthermore, methods for exploring volume data has mostly been designed for experts, which prohibits novice users from exploring volume data. This thesis aims to address these challenges by introducing efficient methods for enhancing salient features through high quality illumination as well as methods for intuitive volume data exploration.

    Humans are interpreting the world around them by observing how light interacts with objects. Shadows enable us to better determine distances while shifts in color enable us to better distinguish objects and identify their shape. These concepts are also applicable to computer generated content. The perception in volume data visualization can therefore be improved by simulating real-world light interaction. This thesis presents efficient methods that are capable of interactively simulating realistic light propagation in volume data. In particular, this work shows how a multi-resolution grid can be used to encode the attenuation of light from all directions using spherical harmonics and thereby enable advanced interactive dynamic light configurations. Two methods are also presented that allow photon mapping calculations to be focused on visually changing areas.The results demonstrate that photon mapping can be used in interactive volume visualization for both static and time-varying volume data.

    Efficient and intuitive exploration of volume data requires methods that are easy to use and reflect the objects that were measured. A value that has been collected by a sensor commonly represents the material existing within a small neighborhood around a location. Recreating the original materials is difficult since the value represents a mixture of them. This is referred to as the partial-volume problem. A method is presented that derives knowledge from the user in order to reconstruct the original materials in a way which is more in line with what the user would expect. Sharp boundaries are visualized where the certainty is high while uncertain areas are visualized with fuzzy boundaries. The volume exploration process of mapping data values to optical properties through the transfer function has traditionally been complex and performed by expert users. A study at a science center showed that visitors favor the presented dynamic gallery method compared to the most commonly used transfer function editor.

    List of papers
    1. A Survey of Volumetric Illumination Techniques for Interactive Volume Rendering
    Open this publication in new window or tab >>A Survey of Volumetric Illumination Techniques for Interactive Volume Rendering
    2014 (English)In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, Vol. 33, no 1, 27-51 p.Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Wiley, 2014
    Keyword
    volume rendering; rendering; volume visualization; visualization; illumination rendering; rendering
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105757 (URN)10.1111/cgf.12252 (DOI)000331694100004 ()
    Available from: 2014-04-07 Created: 2014-04-04 Last updated: 2017-03-17
    2. Efficient Visibility Encoding for Dynamic Illumination in Direct Volume Rendering: -
    Open this publication in new window or tab >>Efficient Visibility Encoding for Dynamic Illumination in Direct Volume Rendering: -
    Show others...
    2012 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 18, no 3, 447-462 p.Article in journal (Refereed) Published
    Abstract [sv]

    We present an algorithm that enables real-time dynamic shading in direct volume rendering using general lighting, includingdirectional lights, point lights and environment maps. real-time performance is achieved by encoding local and global volumetricvisibility using spherical harmonic (SH) basis functions stored in an efficient multi-resolution grid over the extent of the volume. Ourmethod enables high frequency shadows in the spatial domain, but is limited to a low frequency approximation of visibility and illuminationin the angular domain. In a first pass, Level Of Detail (LOD) selection in the grid is based on the current transfer function setting.This enables rapid on-line computation and SH projection of the local spherical distribution of visibility information. Using a piecewiseintegration of the SH coefficients over the local regions, the global visibility within the volume is then computed. By representing thelight sources using their SH projections, the integral over lighting, visibility and isotropic phase functions can be efficiently computedduring rendering. The utility of our method is demonstrated in several examples showing the generality and interactive performanceof the approach.

    Place, publisher, year, edition, pages
    IEEE, 2012
    Keyword
    Volumetric Illumination, Precomputed Radiance Transfer, Volume Rendering
    National Category
    Other Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-66839 (URN)10.1109/TVCG.2011.35 (DOI)000299281700010 ()
    Projects
    CADICSMOVIII
    Note
    ©2011 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Joel Kronander, Daniel Jönsson, Joakim Löw, Patric Ljung, Anders Ynnerman and Jonas Unger, Efficient Visibility Encoding for Dynamic Illumination in Direct Volume Rendering, 2011, IEEE Transactions on Visualization and Computer Graphics. http://dx.doi.org/10.1109/TVCG.2011.35 Available from: 2011-03-24 Created: 2011-03-21 Last updated: 2016-09-19Bibliographically approved
    3. Historygrams: Enabling Interactive Global Illumination in Direct Volume Rendering using Photon Mapping
    Open this publication in new window or tab >>Historygrams: Enabling Interactive Global Illumination in Direct Volume Rendering using Photon Mapping
    2012 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 18, no 12, 2364-2371 p.Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we enable interactive volumetric global illumination by extending photon mapping techniques to handle interactive transfer function (TF) and material editing in the context of volume rendering. We propose novel algorithms and data structures for finding and evaluating parts of a scene affected by these parameter changes, and thus support efficient updates of the photon map. In direct volume rendering (DVR) the ability to explore volume data using parameter changes, such as editable TFs, is of key importance. Advanced global illumination techniques are in most cases computationally too expensive, as they prevent the desired interactivity. Our technique decreases the amount of computation caused by parameter changes, by introducing Historygrams which allow us to efficiently reuse previously computed photon media interactions. Along the viewing rays, we utilize properties of the light transport equations to subdivide a view-ray into segments and independently update them when invalid. Unlike segments of a view-ray, photon scattering events within the volumetric medium needs to be sequentially updated. Using our Historygram approach, we can identify the first invalid photon interaction caused by a property change, and thus reuse all valid photon interactions. Combining these two novel concepts, supports interactive editing of parameters when using volumetric photon mapping in the context of DVR. As a consequence, we can handle arbitrarily shaped and positioned light sources, arbitrary phase functions, bidirectional reflectance distribution functions and multiple scattering which has previously not been possible in interactive DVR.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2012
    Keyword
    Volume rendering, photon mapping, global illumination, participating media
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-86634 (URN)10.1109/TVCG.2012.232 (DOI)000310143100040 ()
    Projects
    CADICSCMIV
    Note

    Funding Agencies|Excellence Center at Linkoping and Lund in Information Technology (ELLIIT)||Swedish e-Science Research Centre (SeRC)||

    Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2017-03-17
    4. Correlated Photon Mapping for Interactive Global Illumination of Time-Varying Volumetric Data
    Open this publication in new window or tab >>Correlated Photon Mapping for Interactive Global Illumination of Time-Varying Volumetric Data
    2017 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 23, no 1, 901-910 p.Article in journal (Refereed) Published
    Abstract [en]

    We present a method for interactive global illumination of both static and time-varying volumetric data based on reduction of the overhead associated with re-computation of photon maps. Our method uses the identification of photon traces invariant to changes of visual parameters such as the transfer function (TF), or data changes between time-steps in a 4D volume. This lets us operate on a variant subset of the entire photon distribution. The amount of computation required in the two stages of the photon mapping process, namely tracing and gathering, can thus be reduced to the subset that are affected by a data or visual parameter change. We rely on two different types of information from the original data to identify the regions that have changed. A low resolution uniform grid containing the minimum and maximum data values of the original data is derived for each time step. Similarly, for two consecutive time-steps, a low resolution grid containing the difference between the overlapping data is used. We show that this compact metadata can be combined with the transfer function to identify the regions that have changed. Each photon traverses the low-resolution grid to identify if it can be directly transferred to the next photon distribution state or if it needs to be recomputed. An efficient representation of the photon distribution is presented leading to an order of magnitude improved performance of the raycasting step. The utility of the method is demonstrated in several examples that show visual fidelity, as well as performance. The examples show that visual quality can be retained when the fraction of retraced photons is as low as 40%-50%.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2017
    Keyword
    Volume rendering, photon mapping, global illumination, participating media
    National Category
    Media Engineering
    Identifiers
    urn:nbn:se:liu:diva-131022 (URN)10.1109/TVCG.2016.2598430 (DOI)000395537600093 ()27514045 (PubMedID)2-s2.0-84999158356 (Scopus ID)
    Projects
    SERCCMIV
    Note

    Funding Agencies|Swedish e-Science Research Centre (SeRC)||Swedish Research Council (VR) grant 2016-05462||Knut and Alice Wallenberg Foundation (KAW) grant 2016-0076||

    Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2017-04-20Bibliographically approved
    5. Boundary Aware Reconstruction of Scalar Fields
    Open this publication in new window or tab >>Boundary Aware Reconstruction of Scalar Fields
    2014 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 20, no 12, 2447-2455 p.Article in journal (Refereed) Published
    Abstract [en]

    In visualization, the combined role of data reconstruction and its classification plays a crucial role. In this paper we propose a novel approach that improves classification of different materials and their boundaries by combining information from the classifiers at the reconstruction stage. Our approach estimates the targeted materials’ local support before performing multiple material-specific reconstructions that prevent much of the misclassification traditionally associated with transitional regions and transfer function (TF) design. With respect to previously published methods our approach offers a number of improvements and advantages. For one, it does not rely on TFs acting on derivative expressions, therefore it is less sensitive to noisy data and the classification of a single material does not depend on specialized TF widgets or specifying regions in a multidimensional TF. Additionally, improved classification is attained without increasing TF dimensionality, which promotes scalability to multivariate data. These aspects are also key in maintaining low interaction complexity. The results are simple-to-achieve visualizations that better comply with the user’s understanding of discrete features within the studied object.

    Place, publisher, year, edition, pages
    IEEE Press, 2014
    National Category
    Computer and Information Science Computer Science
    Identifiers
    urn:nbn:se:liu:diva-110227 (URN)10.1109/TVCG.2014.2346351 (DOI)000344991700090 ()
    Available from: 2014-09-04 Created: 2014-09-04 Last updated: 2016-09-19Bibliographically approved
    6. Intuitive Exploration of Volumetric Data Using Dynamic Galleries
    Open this publication in new window or tab >>Intuitive Exploration of Volumetric Data Using Dynamic Galleries
    2016 (English)In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 22, no 1, 896-905 p.Article in journal (Refereed) Published
    Abstract [en]

    In this work we present a volume exploration method designed to be used by novice users and visitors to science centers and museums. The volumetric digitalization of artifacts in museums is of rapidly increasing interest as enhanced user experience through interactive data visualization can be achieved. This is, however, a challenging task since the vast majority of visitors are not familiar with the concepts commonly used in data exploration, such as mapping of visual properties from values in the data domain using transfer functions. Interacting in the data domain is an effective way to filter away undesired information but it is difficult to predict where the values lie in the spatial domain. In this work we make extensive use of dynamic previews instantly generated as the user explores the data domain. The previews allow the user to predict what effect changes in the data domain will have on the rendered image without being aware that visual parameters are set in the data domain. Each preview represents a subrange of the data domain where overview and details are given on demand through zooming and panning. The method has been designed with touch interfaces as the target platform for interaction. We provide a qualitative evaluation performed with visitors to a science center to show the utility of the approach.

    Place, publisher, year, edition, pages
    IEEE COMPUTER SOC, 2016
    Keyword
    Transfer function; scalar fields; volume rendering; touch interaction; visualization; user interfaces
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-123054 (URN)10.1109/TVCG.2015.2467294 (DOI)000364043400095 ()26390481 (PubMedID)
    Note

    Funding Agencies|Swedish Research Council, VR [2011-5816]; Excellence Center at Linkoping and Lund in Information Technology (ELLIIT); Linnaeus Environment CADICS; Swedish e-Science Research Centre (SeRC)

    Available from: 2015-12-04 Created: 2015-12-03 Last updated: 2016-09-19
  • 39.
    Jönsson, Daniel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Anders, Ynnerman
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Correlated Photon Mapping for Interactive Global Illumination of Time-Varying Volumetric Data2017In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 23, no 1, 901-910 p.Article in journal (Refereed)
    Abstract [en]

    We present a method for interactive global illumination of both static and time-varying volumetric data based on reduction of the overhead associated with re-computation of photon maps. Our method uses the identification of photon traces invariant to changes of visual parameters such as the transfer function (TF), or data changes between time-steps in a 4D volume. This lets us operate on a variant subset of the entire photon distribution. The amount of computation required in the two stages of the photon mapping process, namely tracing and gathering, can thus be reduced to the subset that are affected by a data or visual parameter change. We rely on two different types of information from the original data to identify the regions that have changed. A low resolution uniform grid containing the minimum and maximum data values of the original data is derived for each time step. Similarly, for two consecutive time-steps, a low resolution grid containing the difference between the overlapping data is used. We show that this compact metadata can be combined with the transfer function to identify the regions that have changed. Each photon traverses the low-resolution grid to identify if it can be directly transferred to the next photon distribution state or if it needs to be recomputed. An efficient representation of the photon distribution is presented leading to an order of magnitude improved performance of the raycasting step. The utility of the method is demonstrated in several examples that show visual fidelity, as well as performance. The examples show that visual quality can be retained when the fraction of retraced photons is as low as 40%-50%.

  • 40.
    Kratz, Andrea
    et al.
    Zuse Institute Berlin, Germany.
    Baum, Daniel
    Zuse Institute Berlin, Germany.
    Hotz, Ingrid
    Zuse Institute Berlin, Germany.
    Anisotropic Sampling of Planar and Two-Manifold Domains for Texture Generation and Glyph Distribution2013In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, E-ISSN 1941-0506, Vol. 19, no 11, 1782-1794 p.Article in journal (Refereed)
    Abstract [en]

    We present a new method for the generation of anisotropic sample distributions on planar and two-manifold domains. Most previous work that is concerned with aperiodic point distributions is designed for isotropically shaped samples. Methods focusing on anisotropic sample distributions are rare, and either they are restricted to planar domains, are highly sensitive to the choice of parameters, or they are computationally expensive. In this paper, we present a time-efficient approach for the generation of anisotropic sample distributions that only depends on intuitive design parameters for planar and two-manifold domains. We employ an anisotropic triangulation that serves as basis for the creation of an initial sample distribution as well as for a gravitational-centered relaxation. Furthermore, we present an approach for interactive rendering of anisotropic Voronoi cells as base element for texture generation. It represents a novel and flexible visualization approach to depict metric tensor fields that can be derived from general tensor fields as well as scalar or vector fields.

  • 41.
    Kronander, Joel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gustavson, Stefan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Bonnet, Gerhard
    AG Spheron VR, Germany.
    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.
    A unified framework for multi-sensor HDR video reconstruction2014In: Signal Processing : Image Communications, ISSN 0923-5965, Vol. 29, no 2, 203-215 p.Article in journal (Refereed)
    Abstract [en]

    One of the most successful approaches to modern high quality HDR-video capture is to use camera setups with multiple sensors imaging the scene through a common optical system. However, such systems pose several challenges for HDR reconstruction algorithms. Previous reconstruction techniques have considered debayering, denoising, resampling (alignment) and exposure fusion as separate problems. In contrast, in this paper we present a unifying approach, performing HDR assembly directly from raw sensor data. Our framework includes a camera noise model adapted to HDR video and an algorithm for spatially adaptive HDR reconstruction based on fitting of local polynomial approximations to observed sensor data. The method is easy to implement and allows reconstruction to an arbitrary resolution and output mapping. We present an implementation in CUDA and show real-time performance for an experimental 4 Mpixel multi-sensor HDR video system. We further show that our algorithm has clear advantages over existing methods, both in terms of flexibility and reconstruction quality.

  • 42.
    Kronander, Joel
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Gustavson, Stefan
    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.
    Real-time HDR video reconstruction for multi-sensor systems2012In: ACM SIGGRAPH 2012 Posters, New York, NY, USA: ACM Press, 2012, 65- p.Conference paper (Refereed)
    Abstract [en]

    HDR video is an emerging field of technology, with a few camera systems currently in existence [Myszkowski et al. 2008], Multi-sensor systems [Tocci et al. 2011] have recently proved to be particularly promising due to superior robustness against temporal artifacts, correct motion blur, and high light efficiency. Previous HDR reconstruction methods for multi-sensor systems have assumed pixel perfect alignment of the physical sensors. This is, however, very difficult to achieve in practice. It may even be the case that reflections in beam splitters make it impossible to match the arrangement of the Bayer filters between sensors. We therefor present a novel reconstruction method specifically designed to handle the case of non-negligible misalignments between the sensors. Furthermore, while previous reconstruction techniques have considered HDR assembly, debayering and denoising as separate problems, our method is capable of simultaneous HDR assembly, debayering and smoothing of the data (denoising). The method is also general in that it allows reconstruction to an arbitrary output resolution and mapping. The algorithm is implemented in CUDA, and shows video speed performance for an experimental HDR video platform consisting of four 2336x1756 pixels high quality CCD sensors imaging the scene trough a common optical system. ND-filters of different densities are placed in front of the sensors to capture a dynamic range of 24 f-stops.

  • 43.
    Ljung, Patric
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Winskog, Calle
    Persson, Anders
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundström, Claes
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ynnerman, Anders
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Full Body Virtual Autopsies using a State-of-the-art Volume Rendering Pipeline2006In: IEEE Transactions on Visualization and Computer Graphics, ISSN 1077-2626, Vol. 12, no 5, 869-876 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a procedure for virtual autopsies based on interactive 3D visualizations of large scale, high resolution data from CT-scans of human cadavers. The procedure is described using examples from forensic medicine and the added value and future potential of virtual autopsies is shown from a medical and forensic perspective. Based on the technical demands of the procedure state-of-the-art volume rendering techniques are applied and refined to enable real-time, full body virtual autopsies involving gigabyte sized data on standard GPUs. The techniques applied include transfer function based data reduction using levelof- detail selection and multi-resolution rendering techniques. The paper also describes a data management component for large, out-of-core data sets and an extension to the GPU-based raycaster for efficient dual TF rendering. Detailed benchmarks of the pipeline are presented using data sets from forensic cases.

  • 44.
    Lundberg, Lukas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Art Directed Fluid Flow With Secondary Water Effects2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis describes methods for applying secondary water effects as spray, foam, splashes and mist to a fluid simulation system. For an art direction control over the base fluid flow a Fluid Implicit Particle solver with custom fields is also presented. The methods build upon production techniques within the visual effects industry, fluid dynamics and relevant computer graphics research. The implementation of the methods is created within Side Effects Software Houdini.

  • 45.
    Löwgren, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Technical communication practices in the collaborative mediascape: A case study in media structure transformation2016In: Communication Design Quarterly Review, ISSN 2166-1200, Vol. 4, no 3, 20-25 p.Article in journal (Refereed)
    Abstract [en]

    Professional practices in technical communication are increasingly being challenged by the emergence of collaborative media that enable users to access technical information created by non- professionals. At the same time, these technologies also allow technical communicators to provide a continually expanding audience with knowledge and skills needed now more than ever. Through a co-design case study, researchers developed a new and innovative platform for producing and distributing technical information including user-generated content. Moreover, the events of the case included market strategies in which a professional organization moved from a reactive to a more proactive position on collaborative media. In so doing, they outlined a set of new professional roles for technical communicators including editors, curators, facilitators, and community managers.

  • 46.
    Manker, Jon
    et al.
    Södertörns högskola, Institutionen för kommunikation, medier och IT, Medieteknik.
    Arvola, Mattias
    Linköping University, Department of Computer and Information Science, MDALAB - Human Computer Interfaces. Linköping University, The Institute of Technology.
    Prototyping in game design: Externalization and internalization of game ideas2011In: HCI 2011: Health, Wealth & Happiness: The 25th BCS Conference on Human-Computer Interaction. Newcastle Upon Tyne, UK, July 4-8, 2011., 2011Conference paper (Refereed)
    Abstract [en]

    Prototyping is a well-studied activity for interaction designers, but its role in computer game design is relatively unexplored. The aim of this study is to shed light on prototyping in game design. Interviews were conducted with 27 game designers. The empirical data was structured using qualitative content analysis and analysed using the design version of The Activity Checklist. The analysis indicated that six categories of the checklist were significant for the data obtained. Thesecategories are presented in relation to the data. The roles of externalization and internalization are specifically highlighted.

  • 47.
    Manuylova, Ekaterina
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Investigations of stereo setup for Kinect2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The main purpose of this work is to investigate the behavior of the recently released by Microsoft company the Kinect sensor, which contains the properties that go beyond ordinary cameras. Normally, in order to create a 3D reconstruction of the scene two cameras are required. Whereas, the Kinect device, due to the properties of the Infrared projector and sensor allows to create the same type of the reconstruction using only one device. However, the depth images, which are generated by the Infrared laser projector and monochrome sensor in Kinect can contain undefined values. Therefore, in addition to other investigations this project contains an idea how to improve the quality of the depth images. However, the base aim of this work is to perform a reconstruction of the scene based on the color images using pair of Kinects which will be compared with the results generated by using depth information from one Kinect. In addition, the report contains the information how to check that all the performed calculations were done correctly. All  the algorithms which were used in the project as well as the achieved results will be described and discussed in the separate chapters in the current report.

  • 48.
    Miandji, Ehsan
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Surface Light Field Generation, Compression and Rendering2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We present a framework for generating, compressing and rendering of SurfaceLight Field (SLF) data. Our method is based on radiance data generated usingphysically based rendering methods. Thus the SLF data is generated directlyinstead of re-sampling digital photographs. Our SLF representation decouplesspatial resolution from geometric complexity. We achieve this by uniform samplingof spatial dimension of the SLF function. For compression, we use ClusteredPrincipal Component Analysis (CPCA). The SLF matrix is first clustered to lowfrequency groups of points across all directions. Then we apply PCA to eachcluster. The clustering ensures that the within-cluster frequency of data is low,allowing for projection using a few principal components. Finally we reconstructthe CPCA encoded data using an efficient rendering algorithm. Our reconstructiontechnique ensures seamless reconstruction of discrete SLF data. We applied ourrendering method for fast, high quality off-line rendering and real-time illuminationof static scenes. The proposed framework is not limited to complexity of materialsor light sources, enabling us to render high quality images describing the full globalillumination in a scene.

  • 49.
    Miandji, Ehsan
    et al.
    Linköping University, Department of Science and Technology, Media and Information 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.
    Unger, Jonas
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Geometry Independent Surface Light Fields for Real TimeRendering of Precomputed Global Illumination2011In: Proceedings of SGRAD 2011 / [ed] Thomas Larsson, Lars Kjelldahl, Kai-Mikael Jää-Aro, Royal Institute of Technology, Stockholm, 2011, 27-34 p.Conference paper (Refereed)
    Abstract [en]

    We present a framework for generating, compressing and rendering of Surface Light Field (SLF) data. Our methodis based on radiance data generated using physically based rendering methods. Thus the SLF data is generateddirectly instead of re-sampling digital photographs. Our SLF representation decouples spatial resolution fromgeometric complexity. We achieve this by uniform sampling of spatial dimension of the SLF function. For compression,we use Clustered Principal Component Analysis (CPCA). The SLF matrix is first clustered to low frequencygroups of points across all directions. Then we apply PCA to each cluster. The clustering ensures that the withinclusterfrequency of data is low, allowing for projection using a few principal components. Finally we reconstructthe CPCA encoded data using an efficient rendering algorithm. Our reconstruction technique ensures seamlessreconstruction of discrete SLF data. We applied our rendering method for fast, high quality off-line rendering andreal-time illumination of static scenes. The proposed framework is not limited to complexity of materials or lightsources, enabling us to render high quality images describing the full global illumination in a scene.

  • 50.
    Miandji, Ehsan
    et al.
    Sharif University of Technology, Tehran, Iran.
    Sargazi Moghaddam, Mohammad Hadi
    Sharif University of Technology, Tehran, Iran.
    Samavati, Faramarz
    University of Calgary, Calgary, Alberta, Canada.
    Emadi, Mohammad
    Sharif University of Technology, Tehran, Iran.
    Real-time multi-band synthesis of ocean water with new iterative up-sampling technique2009In: The Visual Computer, ISSN 0178-2789, E-ISSN 1432-2315, Vol. 25, no 5-7, 697-705 p.Article in journal (Refereed)
    Abstract [en]

    Adapting natural phenomena rendering for realtime applications has become a common practice in computer graphics. We propose a GPU-based multi-band methodfor optimized synthesis of “far from coast” ocean waves using an empirical Fourier domain model. Instead of performing two independent syntheses for low- and high-band frequencies of ocean waves, we perform only low-band synthesis and employ results to reproduce high frequency details ofocean surface by an optimized iterative up-sampling stage.Our experimental results show that this approach greatlyimproves the performance of original multi-band synthesiswhile maintaining image quality.

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