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Performance Relighting and Reflectance Transformation with Time-Multiplexed Illumination
University of Southern California Institute for Creative Technologies.
University of Southern California Institute for Creative Technologies.
University of Southern California Institute for Creative Technologies.
University of Southern California .ORCID iD: 0000-0002-7765-1747
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2005 (English)In: ACM Transactions on Graphics, ISSN 0730-0301, E-ISSN 1557-7368, Vol. 24, no 3Article in journal (Refereed) Published
Abstract [en]

We present a technique for capturing an actor’s live-action performance in such a way that the lighting and reflectance of the actor can be designed and modified in postproduction. Our approach is to illuminate the subject with a sequence of time-multiplexed basis lighting conditions, and to record these conditions with a highspeed video camera so that many conditions are recorded in the span of the desired output frame interval. We investigate several lighting bases for representing the sphere of incident illumination using a set of discrete LED light sources, and we estimate and compensate for subject motion using optical flow and image warping based on a set of tracking frames inserted into the lighting basis. To composite the illuminated performance into a new background, we include a time-multiplexed matte within the basis. We also show that the acquired data enables time-varying surface normals, albedo, and ambient occlusion to be estimated, which can be used to transform the actor’s reflectance to produce both subtle and stylistic effects.

Place, publisher, year, edition, pages
2005. Vol. 24, no 3
Keyword [en]
Relighting, compositing, environmental illumination, image-based rendering, reflectance models
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-16283DOI: 10.1145/1073204.1073258OAI: oai:DiVA.org:liu-16283DiVA: diva2:133595
Available from: 2009-01-13 Created: 2009-01-13 Last updated: 2015-09-22Bibliographically approved
In thesis
1. Incident Light Fields
Open this publication in new window or tab >>Incident Light Fields
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Image based lighting, (IBL), is a computer graphics technique for creating photorealistic renderings of synthetic objects such that they can be placed into real world scenes. IBL has been widely recognized and is today used in commercial production pipelines. However, the current techniques only use illumination captured at a single point in space. This means that traditional IBL cannot capture or recreate effects such as cast shadows, shafts of light or other important spatial variations in the illumination. Such lighting effects are, in many cases, artistically created or are there to emphasize certain features, and are therefore a very important part of the visual appearance of a scene.

This thesis and the included papers present methods that extend IBL to allow for capture and rendering with spatially varying illumination. This is accomplished by measuring the light field incident onto a region in space, called an Incident Light Field, (ILF), and using it as illumination in renderings. This requires the illumination to be captured at a large number of points in space instead of just one. The complexity of the capture methods and rendering algorithms are then significantly increased.

The technique for measuring spatially varying illumination in real scenes is based on capture of High Dynamic Range, (HDR), image sequences. For efficient measurement, the image capture is performed at video frame rates. The captured illumination information in the image sequences is processed such that it can be used in computer graphics rendering. By extracting high intensity regions from the captured data and representing them separately, this thesis also describes a technique for increasing rendering efficiency and methods for editing the captured illumination, for example artificially moving or turning on and of individual light sources.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2009. 97 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1233
Keyword
Computer Graphics, Image Based Lighting, Photorealistic Rendering, Light Fields, High Dynamic Range Imaging
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-16287 (URN)978-91-7393-717-7 (ISBN)
Public defence
2009-01-30, K3, Kåkenhus, Campus Norrköping, Linköpings universitet, Norrköping, 10:15 (English)
Opponent
Supervisors
Available from: 2009-01-13 Created: 2009-01-13 Last updated: 2016-08-31Bibliographically approved

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Unger, Jonas

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