EGSR06: 17th Eurographics Symposium on Rendering
Permanent URI for this collection
Reconstruction of Volumetric Surface Textures for Real-Time Rendering
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Magda, Sebastian
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Kriegman, David
Sparse Lumigraph Relighting by Illumination and Reflectance Estimation from Multi-View Images
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Yu, Tianli
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Wang, Hongcheng
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Ahuja, Narendra
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Chen, Wei-Chao
An Efficient Multi-View Rasterization Architecture
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Hasselgren, Jon
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Akenine-Möller, Tomas
Tomographic Reconstruction of Transparent Objects
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Trifonov, Borislav
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Bradley, Derek
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Heidrich, Wolfgang
Antialiasing for Automultiscopic 3D Displays
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Zwicker, Matthias
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Matusik, Wojciech
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Durand, Frédo
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Pfister, Hanspeter
Real-time Multi-perspective Rendering on Graphics Hardware
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Hou, Xianyou
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Wei, Li-Yi
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Shum, Heung-Yeung
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Guo, Baining
Two Stage Importance Sampling for Direct Lighting
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Cline, David
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Egbert, Parris K.
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Talbot, Justin F.
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Cardon, David L.
Making Radiance and Irradiance Caching Practical: Adaptive Caching and Neighbor Clamping
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Krivánek, Jaroslav
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Bouatouch, Kadi
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Pattanaik, Sumanta
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Zára, Jirí
Sequential Sampling for Dynamic Environment Map Illumination
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Ghosh, Abhijeet
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Doucet, Arnaud
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Heidrich, Wolfgang
Instant Ray Tracing: The Bounding Interval Hierarchy
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Wächter, Carsten
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Keller, Alexander
Exploiting Temporal Coherence for Incremental All-Frequency Relighting
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Overbeck, Ryan
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Ben-Artzi, Aner
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Ramamoorthi, Ravi
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Grinspun, Eitan
Wavelet Radiance Transport for Interactive Indirect Lighting
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Kontkanen, Janne
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Turquin, Emmanuel
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Holzschuch, Nicolas
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Sillion, François X.
Adaptive Visibility-Driven View Cell Construction
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Mattausch, Oliver
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Bittner, Jirí
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Wimmer, Michael
Relighting Human Locomotion with Flowed Reflectance Fields
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Einarsson, Per
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Chabert, Charles-Felix
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Jones, Andrew
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Ma, Wan-Chun
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Lamond, Bruce
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Hawkins, Tim
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Bolas, Mark
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Sylwan, Sebastian
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Debevec, Paul
Efficient Wavelet Rotation for Environment Map Rendering
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Wang, Rui
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Ng, Ren
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Luebke, David
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Humphreys, Greg
Near Optimal Hierarchical Culling: Performance Driven Use of Hardware Occlusion Queries
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Guthe, Michael
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Balázs, Ákos
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Klein, Reinhard
Warping and Partitioning for Low Error Shadow Maps
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Lloyd, D. Brandon
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Tuft, David
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Yoon, Sung-eui
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Manocha, Dinesh
Practical, Real-time Studio Matting using Dual Imagers
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McGuire, Morgan
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Matusik, Wojciech
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Yerazunis, William
Real-time Soft Shadow Mapping by Backprojection
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Guennebaud, Gaël
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Barthe, Loïc
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Paulin, Mathias
Surface Enhancement Using Real-time Photometric Stereo and Reflectance Transformation
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Malzbender, Tom
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Wilburn, Bennett
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Gelb, Dan
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Ambrisco, Bill
Symmetric Photography: Exploiting Data-sparseness in Reflectance Fields
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Garg, Gaurav
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Talvala, Eino-Ville
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Levoy, Marc
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Lensch, Hendrik P. A.
Spatio-Angular Resolution Tradeoffs in Integral Photography
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Georgeiv, Todor
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Zheng, Ke Colin
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Curless, Brian
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Salesin, David
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Nayar, Shree
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Intwala, Chintan
Texture Transfer Using Geometry Correlation
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Mertens, Tom
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Kautz, Jan
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Chen, Jiawen
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Bekaert, Philippe
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Durand, Frédo
Texture Replacement of Garments in Monocular Video
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Scholz, Volker
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Magnor, Marcus
A GPU-driven Algorithm for Accurate Interactive Reflections on Curved Objects
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Estalella, Pau
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Martin, Ignacio
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Drettakis, George
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Tost, Dani
A Novel Method for Fast and High-Quality Rendering of Hair
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Xu, Songhua
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Lau, Francis C. M.
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Jiang, Hao
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Pan, Yunhe
Interactive Screen-Space Accurate Photon Tracing on GPUs
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Krüger, Jens
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Bürger, Kai
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Westermann, Rüdiger
Ardeco: Automatic Region DEtection and COnversion
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Lecot, Gregory
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Levy, Bruno
Segmentation-Based 3D Artistic Rendering
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Kolliopoulos, Alexander
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Wang, Jack M.
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Hertzmann, Aaron
Bidirectional Instant Radiosity
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Segovia, Benjamin
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Iehl, Jean Claude
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Mitanchey, Richard
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Péroche, Bernard
Painting With Texture
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Ritter, Lincoln
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Li, Wilmot
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Curless, Brian
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Agrawala, Maneesh
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Salesin, David
Directing Gaze in 3D Models with Stylized Focus
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Cole, Forrester
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DeCarlo, Doug
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Finkelstein, Adam
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Kin, Kenrick
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Morley, Keith
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Santella, Anthony
Image-driven Navigation of Analytical BRDF Models
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Ngan, Addy
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Durand, Frédo
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Matusik, Wojciech
Browse
Recent Submissions
Item Visual Chatter in the Real World(The Eurographics Association, 2006) Nayar, Shree K.; Krishnan, Gurunandan G.; Tomas Akenine-Moeller and Wolfgang HeidrichWhen a scene is lit by a source of light, the radiance of each point in the scene can be viewed as having two components, namely, direct and global. Recently, an efFIcient separation method has been proposed that uses high frequency illumination patterns to measure the direct and global components of a scene. The global component could arise from not only interreflections but also subsurface scattering within translucent surfaces and volumetric scattering by participating media. In this paper, we use this method to measure the direct and global components of a variety of natural and man-made materials. The computed direct and global images provide interesting insights into the scattering properties of common real-world materials. We have also measured the two components for a 3D texture as a function of lighting direction. This experiment shows that the global component of a BTF tends vary smoothly with respect to the lighting direction compared to the direct component of the BTF. Finally, we apply the separation method to a translucent object for different imaging and illumination scales (resolutions). The results obtained show how the BSSDRF of the object gradually reduces to a BRDF as one goes from fine to coarse scale. All the measurement results reported here, as well as several others, can be viewed as high resolution images at http://www1.cs.columbia.edu/CAVE/projects/separation/separation.php.Item Handheld Pixels(The Eurographics Association, 2006) Nordlund, Petri; Tomas Akenine-Moeller and Wolfgang HeidrichDuring this decade, pixels have become mobile. Cell phones, PDAs, handheld gaming consoles and other similar devices start to have color displays by standard and color displays are hungry for high-quality graphics. QVGA and VGA display resolutions are common, requiring dedicated hardware for graphics acceleration. Color displays and open platforms also invite games and other applications, which build on the availability of robust graphics. Handheld graphics acceleration is close to its desktop and games console counterparts - with content running on an embedded version of OpenGL, the OpenGL ES 2.0, vertex and pixel shaders are a requirement. Floating-point accuracy, lots of texture surfaces, plenty of performance - handheld pixels are of good quality and there are lots of them. Handheld gaming drives the handheld 3D graphics performance, but unlike on desktops, vector graphics hardware acceleration will become an even widely spread requirement on new handheld platforms. Applications such as the device's main graphical user interface and interactive maps are driving these requirements. In addition to performance, a strong driver for vector graphics on handhelds is image quality. The first handheld devices, including cell phones, with dedicated 3D graphics accelerators have already hit the market. By 2010, a large number of new cell phones and PDAs will be enabled with hardware vector- and 3D graphics acceleration. The volume of graphics acceleration enabled silicon chips shipping for handheld devices is expected to be significantly higher than for desktop PCs and gaming consoles. This creates a lucrative platform for game and application developers who want to develop handheld content with high-quality graphics. As there are numerous different handheld devices, the industry is fighting against fragmentation - widely adopted platforms must be created to enable universal content development across a wide range of platforms and end devices - the platform race is already on. All in all, the industry is busy creating all the essential components to bring high-quality programmable pixels to handheld devices. Content developers are already up-to speed to provide winning content for these devices. All in all, the future of handheld pixels looks rosy!Item Reconstruction of Volumetric Surface Textures for Real-Time Rendering(The Eurographics Association, 2006) Magda, Sebastian; Kriegman, David; Tomas Akenine-Moeller and Wolfgang HeidrichVolumetric texturing is a popular technique for rendering rich 3-D detail when a polygonal surface representation would be ineffective. Although efficient algorithms for rendering volumetric textures have been known for years, capturing the richness of a real-life volumetric materials remains a challenging problem. In this paper we propose a technique for generating a volumetric representation of a complex 3-D texture with unknown reflectance and structure. From acquired reflectance data in the form of a 6-D Bidirectional Texture Function (BTF), the proposed algorithm creates an efficient volumetric representation in the form of a stack of semi-transparent layers each representing a slice through the texture s volume. In addition to negligible storage requirements, this representation is ideally suited for hardware-accelerated real-time rendering.Item Statistical Acquisition of Texture Appearance(The Eurographics Association, 2006) Ngan, Addy; Durand, Frédo; Tomas Akenine-Moeller and Wolfgang HeidrichWe propose a simple method to acquire and reconstruct material appearance with sparsely sampled data. Our technique renders elaborate view- and light-dependent effects and faithfully reproduces materials such as fabrics and knitwears. Our approach uses sparse measurements to reconstruct a full six-dimensional Bidirectional Texture Function (BTF). Our reconstruction only require input images from the top view to be registered, which is easy to achieve with a fixed camera setup. Bidirectional properties are acquired from a sparse set of viewing directions through image statistics and therefore precise registrations for these views are unnecessary. Our technique is based on multi-scale histograms of image pyramids. The full BTF is generated by matching the corresponding pyramid histograms to interpolated top-view images.We show that the use of multi-scale image statistics achieves a visually plausible appearance. However, our technique does not fully capture sharp specularities or the geometric aspects of parallax. Nonetheless, a large class of materials can be reproduced well with our technique, and our statistical characterization enables acquisition of such materials efficiently using a simple setup.Item Sparse Lumigraph Relighting by Illumination and Reflectance Estimation from Multi-View Images(The Eurographics Association, 2006) Yu, Tianli; Wang, Hongcheng; Ahuja, Narendra; Chen, Wei-Chao; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a novel relighting approach that does not assume that the illumination is known or controllable. Instead, we estimate the illumination and texture from given multi-view images captured under a single illumination setting, given the object shape. We rely on the viewpoint-dependence of surface reflectance to resolve the usual texture-illumination ambiguity. The task of obtaining the illumination and texture models is formulated as the decomposition of the observed surface radiance tensor into the product of a light transport tensor, and illumination and texture matrices. We estimate both the illumination and texture at the same time by solving a system of bilinear equations. To reduce estimation error due to imperfect input surface geometry, we also perform a multi-scale discrete search on the specular surface normal. Our results on synthetic and real data indicate that we can estimate the illumination, the diffuse as well as the specular components of the surface texture map (up to a global scaling ambiguity). Our approach allows more flexibilities in rendering novel images, such as view changing, and light and texture editing.Item An Efficient Multi-View Rasterization Architecture(The Eurographics Association, 2006) Hasselgren, Jon; Akenine-Möller, Tomas; Tomas Akenine-Moeller and Wolfgang HeidrichTV have been designed and built. However, these displays have received relatively little attention in the context of real-time computer graphics. We present a novel rasterization architecture that rasterizes each triangle to multiple views simultaneously. When determining which tile in which view to rasterize next, we use an efficiency measure that estimates which tile is expected to get the most hits in the texture cache. Once that tile has been rasterized, the efficiency measure is updated, and a new tile and view are selected. Our traversal algorithm provides significant reductions in the amount of texture fetches, and bandwidth gains on the order of a magnitude have been observed. We also present an approximate rasterization algorithm that avoids pixel shader evaluations for a substantial amount (up to 95%) of fragments and still maintains high image quality.Item Tomographic Reconstruction of Transparent Objects(The Eurographics Association, 2006) Trifonov, Borislav; Bradley, Derek; Heidrich, Wolfgang; Tomas Akenine-Moeller and Wolfgang HeidrichThe scanning of 3D geometry has become a popular way of capturing the shape of real-world objects. Transparent objects, however, pose problems for traditional scanning methods. We present a visible light tomographic reconstruction method for recovering the shape of transparent objects, such as glass. Our setup is relatively simple to implement, and accounts for refraction, which can be a significant problem in visible light tomography.Item Automatic Multiperspective Images(The Eurographics Association, 2006) Román, Augusto; Lensch, Hendrik P. A.; Tomas Akenine-Moeller and Wolfgang HeidrichMultiperspective images generated from a collection of photographs or a videostream can be used to effectively summarize long, roughly planar scenes such as city streets. The final image will span a larger field of view than any single input image. However, common projections used to make these images, including cross-slits and pushbroom projections, may suffer from depth-related distortions in non-planar scenes. In this paper, we use an aspect-ratio distortion metric to compare these images to standard perspective projections. By minimizing this error metric we can automatically define the picture surface and viewpoints of a multiperspective image that reduces distortion artifacts. This optimization requires only a coarse estimate of scene geometry which can be provided as a depth map or a 2D spatial importance map defining interesting parts of the scene. These maps can be automatically constructed in most cases, allowing rapid generation of images of very long scenes.Item Antialiasing for Automultiscopic 3D Displays(The Eurographics Association, 2006) Zwicker, Matthias; Matusik, Wojciech; Durand, Frédo; Pfister, Hanspeter; Tomas Akenine-Moeller and Wolfgang HeidrichAutomultiscopic displays show stereoscopic images that can be viewed from any viewpoint without special glasses. They hold great promise for the future of television and digital entertainment. However, the image quality on these 3D displays is currently not sufficient to appeal to the mass market. In this paper, we extend the frequency analysis of light fields to address some of the major issues in 3D cinematography for automultiscopic displays. First, we derive the bandwidth of 3D displays using ray-space analysis, and we introduce a method to quantify display depth of field. We show that this approach provides solid foundations to analyze and distinguish various aspects of aliasing. We then present an anti-aliasing technique for automultiscopic displays by combining a reconstruction and a display prefilter. Next, we show how to reparameterize multi-view inputs to optimally match the depth of field of a display to improve the image quality. Finally, we present guidelines for 3D content acquisition, such as optimal multi-view camera configuration and placement.Item Real-time Multi-perspective Rendering on Graphics Hardware(The Eurographics Association, 2006) Hou, Xianyou; Wei, Li-Yi; Shum, Heung-Yeung; Guo, Baining; Tomas Akenine-Moeller and Wolfgang HeidrichMulti-perspective rendering has a variety of applications; examples include lens refraction, curved mirror re- flection, caustics, as well depiction and visualization. However, multi-perspective rendering is not yet practical on polygonal graphics hardware, which so far has utilized mostly single-perspective (pin-hole or orthographic) projections. In this paper, we present a methodology for real-time multi-perspective rendering on polygonal graphics hardware. Our approach approximates a general multi-perspective projection surface (such as a curved mirror and lens) via a piecewise-linear triangle mesh, upon which each triangle is a simple multi-perspective camera, parameterized by three rays at triangle vertices. We derive analytic formula showing that each triangle projection can be implemented as a pair of vertex and fragment programs on programmable graphics hardware. We demonstrate real-time performance of a variety of applications enabled by our technique, including reflection, refraction, caustics, and visualization.Item Two Stage Importance Sampling for Direct Lighting(The Eurographics Association, 2006) Cline, David; Egbert, Parris K.; Talbot, Justin F.; Cardon, David L.; Tomas Akenine-Moeller and Wolfgang HeidrichWe describe an importance sampling method to generate samples based on the product of a BRDF and an environment map or large light source. The method works by creating a hierarchical partition of the light source based on the BRDF function for each primary (eye) ray in a ray tracer. This partition, along with a summed area table of the light source, form an approximation to the product function that is suitable for importance sampling. The partition is used to guide a sample warping algorithm to transform a uniform distribution of points so that they approximate the product distribution. The technique is unbiased, requires little precomputation, and we demonstrate that it works well for a variety of BRDF types. Further, we present an adaptive method which allocates varying numbers of samples to different image pixels to reduce shadow artifacts.Item Making Radiance and Irradiance Caching Practical: Adaptive Caching and Neighbor Clamping(The Eurographics Association, 2006) Krivánek, Jaroslav; Bouatouch, Kadi; Pattanaik, Sumanta; Zára, Jirí; Tomas Akenine-Moeller and Wolfgang HeidrichRadiance and irradiance caching are efficient global illumination algorithms based on interpolating indirect illumination from a sparse set of cached values. In this paper we propose an adaptive algorithm for guiding spatial density of the cached values in radiance and irradiance caching. The density is adapted to the rate of change of indirect illumination in order to avoid visible interpolation artifacts and produce smooth interpolated illumination. In addition, we discuss some practical problems arising in the implementation of radiance and irradiance caching, and propose techniques for solving those problems. Namely, the neighbor clamping heuristic is proposed as a robust means for detecting small sources of indirect illumination and for dealing with problems caused by ray leaking through small gaps between adjacent polygons.Item Sequential Sampling for Dynamic Environment Map Illumination(The Eurographics Association, 2006) Ghosh, Abhijeet; Doucet, Arnaud; Heidrich, Wolfgang; Tomas Akenine-Moeller and Wolfgang HeidrichSampling complex illumination in the form of environment maps has received a lot of attention in computer graphics. Recent work in this area has demonstrated that drawing samples from the product of light and BRDF produces superior results to other sampling strategies. However, existing methods in this area consider only individual frames, and do not take advantage of coherence in animations. In this paper, we introduce a sequential sampling approach for dynamic environment map illumination. Our algorithm efficiently samples from the product of illumination and BRDF, while exploiting temporal coherence. We demonstrate significant performance benefits over existing methods.Item Instant Ray Tracing: The Bounding Interval Hierarchy(The Eurographics Association, 2006) Wächter, Carsten; Keller, Alexander; Tomas Akenine-Moeller and Wolfgang HeidrichWe introduce a new ray tracing algorithm that exploits the best of previous methods: Similar to bounding volume hierarchies the memory of the acceleration data structure is linear in the number of objects to be ray traced and can be predicted prior to construction, while the traversal of the hierarchy is as efficient as the one of kd-trees. The construction algorithm can be considered a variant of quicksort and for the first time is based on a global space partitioning heuristic, which is much cheaper to evaluate than the classic surface area heuristic. Compared to spatial partitioning schemes only a fraction of the memory is used and a higher numerical precision is intrinsic. The new method is simple to implement and its high performance is demonstrated by extensive measurements including massive as well as dynamic scenes, where we focus on the total time to image including the construction cost rather than on only frames per second.Item Exploiting Temporal Coherence for Incremental All-Frequency Relighting(The Eurographics Association, 2006) Overbeck, Ryan; Ben-Artzi, Aner; Ramamoorthi, Ravi; Grinspun, Eitan; Tomas Akenine-Moeller and Wolfgang HeidrichPrecomputed radiance transfer (PRT) enables all-frequency relighting with complex illumination, materials and shadows. To achieve real-time performance, PRT exploits angular coherence in the illumination, and spatial coherence in the light transport. Temporal coherence of the lighting from frame to frame is an important, but unexplored additional form of coherence for PRT. In this paper, we develop incremental methods for approximating the differences in lighting between consecutive frames. We analyze the lighting wavelet decomposition over typical motion sequences, and observe differing degrees of temporal coherence across levels of the wavelet hierarchy. To address this, our algorithm treats each level separately, adapting to available coherence. The proposed method is orthogonal to other forms of coherence, and can be added to almost any all-frequency PRT algorithm with minimal implementation, computation or memory overhead. We demonstrate our technique within existing codes for nonlinear wavelet approximation, changing view with BRDF factorization, and clustered PCA. Exploiting temporal coherence of dynamic lighting yields a 3×-4× performance improvement, e.g., all-frequency effects are achieved with 30 wavelet coefficients per frame for the lighting, about the same as low-frequency spherical harmonic methods. Distinctly, our algorithm smoothly converges to the exact result within a few frames of the lighting becoming static.Item Wavelet Radiance Transport for Interactive Indirect Lighting(The Eurographics Association, 2006) Kontkanen, Janne; Turquin, Emmanuel; Holzschuch, Nicolas; Sillion, François X.; Tomas Akenine-Moeller and Wolfgang HeidrichGlobal illumination is a complex all-frequency phenomenon including subtle effects caused by indirect lighting. Computing global illumination interactively for dynamic lighting conditions has many potential applications, notably in architecture, motion pictures and computer games. It remains a challenging issue, despite the considerable amount of research work devoted to finding efficient methods. This paper presents a novel method for fast computation of indirect lighting; combined with a separate calculation of direct lighting, we provide interactive global illumination for scenes with diffuse and glossy materials, and arbitrarily distributed point light sources. To achieve this goal, we introduce three new tools: a 4D wavelet basis for concise radiance expression, an efficient hierarchical pre-computation of the Global Transport Operator representing the entire propagation of radiance in the scene in a single operation, and a run-time projection of direct lighting on to our wavelet basis. The resulting technique allows unprecedented freedom in the interactive manipulation of lighting for static scenes.Item Adaptive Visibility-Driven View Cell Construction(The Eurographics Association, 2006) Mattausch, Oliver; Bittner, Jirí; Wimmer, Michael; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a new method for the automatic partitioning of view space into a multi-level view cell hierarchy. We use a cost-based model in order to minimize the average rendering time. Unlike previous methods, our model takes into account the actual visibility in the scene, and the partition is not restricted to planes given by the scene geometry. We show that the resulting view cell hierarchy works for different types of scenes and gives lower average rendering time than previously used methods.Item Relighting Human Locomotion with Flowed Reflectance Fields(The Eurographics Association, 2006) Einarsson, Per; Chabert, Charles-Felix; Jones, Andrew; Ma, Wan-Chun; Lamond, Bruce; Hawkins, Tim; Bolas, Mark; Sylwan, Sebastian; Debevec, Paul; Tomas Akenine-Moeller and Wolfgang HeidrichWe present an image-based approach for capturing the appearance of a walking or running person so they can be rendered realistically under variable viewpoint and illumination. In our approach, a person walks on a treadmill at a regular rate as a turntable slowly rotates the person s direction. As this happens, the person is filmed with a vertical array of high-speed cameras under a time-multiplexed lighting basis, acquiring a seven-dimensional dataset of the person under variable time, illumination, and viewing direction in approximately forty seconds. We process this data into a flowed reflectance field using an optical flow algorithm to correspond pixels in neighboring camera views and time samples to each other, and we use image compression to reduce the size of this data.We then use image-based relighting and a hardware-accelerated combination of view morphing and light field rendering to render the subject under user-specified viewpoint and lighting conditions. To composite the person into a scene, we use an alpha channel derived from back lighting and a retroreflective treadmill surface and a visual hull process to render the shadows the person would cast onto the ground. We demonstrate realistic composites of several subjects into real and virtual environments using our technique.Item Efficient Wavelet Rotation for Environment Map Rendering(The Eurographics Association, 2006) Wang, Rui; Ng, Ren; Luebke, David; Humphreys, Greg; Tomas Akenine-Moeller and Wolfgang HeidrichReal-time shading with environment maps requires the ability to rotate the global lighting to each surface point's local coordinate frame. Although extensive previous work has studied rotation of functions represented by spherical harmonics, little work has investigated efficient rotation of wavelets. Wavelets are superior at approximating high frequency signals such as detailed high dynamic range lighting and very shiny BRDFs, but present difficulties for interactive rendering due to the lack of an analytic solution for rotation. In this paper we present an efficient computational solution for wavelet rotation using precomputed matrices. Each matrix represents the linear transformation of source wavelet bases defined in the global coordinate frame to target wavelet bases defined in sampled local frames. Since wavelets have compact support, these matrices are very sparse, enabling efficient storage and fast computation at run-time. In this paper, we focus on the application of our technique to interactive environment map rendering. We show that using these matrices allows us to evaluate the integral of dynamic lighting with dynamic BRDFs at interactive rates, incorporating efficient non-linear approximation of both illumination and reflection. Our technique improves on previous work by eliminating the need for prefiltering environment maps, and is thus significantly faster for accurate rendering of dynamic environment lighting with high frequency reflection effects.Item Near Optimal Hierarchical Culling: Performance Driven Use of Hardware Occlusion Queries(The Eurographics Association, 2006) Guthe, Michael; Balázs, Ákos; Klein, Reinhard; Tomas Akenine-Moeller and Wolfgang HeidrichThe most efficient general occlusion culling techniques are based on hardware accelerated occlusion queries. Although in many cases these techniques can considerably improve performance, they may still reduce efficiency compared to simple view frustum culling, especially in the case of low depth complexity. This prevented the broad use of occlusion culling in most commercial applications. In this paper we present a new conservative method to solve this problem, where the main idea is to use a statistical model describing the occlusion probability for each occlusion query in order to reduce the number of wasted queries which are the reason for the reduction in rendering speed. We also describe an abstract parameterized model for the graphics hardware performance. The parameters are easily measurable at startup and thus the model can be adapted to the graphics hardware in use. Combining this model with the estimated occlusion probability our method is able to achieve a near optimal scheduling of the occlusion queries. The implementation of the algorithm is straightforward and it can be easily integrated in existing real-time rendering packages based on common hierarchical data structures.Item Warping and Partitioning for Low Error Shadow Maps(The Eurographics Association, 2006) Lloyd, D. Brandon; Tuft, David; Yoon, Sung-eui; Manocha, Dinesh; Tomas Akenine-Moeller and Wolfgang HeidrichWe evaluate several shadow map algorithms based on warping and partitioning using the maximum perspective aliasing error over the entire view frustum. With respect to our error metric, we show that a range of warping parameters corresponding to several previous warping algorithms have the same error. We also analyze several partitioning schemes to determine which produces the least maximum error using the least number of partitions. Finally, we show how warping and partitioning can be combined for interactive rendering of low error shadows in scenes with a high depth range.Item Practical, Real-time Studio Matting using Dual Imagers(The Eurographics Association, 2006) McGuire, Morgan; Matusik, Wojciech; Yerazunis, William; Tomas Akenine-Moeller and Wolfgang HeidrichThis paper presents a practical system for capturing high-resolution video mattes using cameras that contain two imagers on one optical axis. The dual imagers capture registered frames that differ only by defocus or polarization at pixels corresponding to special background gray-screens. This system eliminates color spill and other drawbacks of blue-screen matting while preserving many of its desirable properties (e.g., unassisted, real-time, natural illumination) over more recent methods, and achieving higher precision output for Bayer-filter digital cameras. Because two imagers capture more information than one, we are able to automatically process scenes that would require manual retouching with blue- screen matting. The dual-imager system successfully pulls mattes for scenes containing thin hair, liquids, glass, and reflective objects; mirror reflections produce incorrect results. We show result comparisons for these scenes against blue-screen matting and describe materials and patterns for building a capture system.Item Real-time Soft Shadow Mapping by Backprojection(The Eurographics Association, 2006) Guennebaud, Gaël; Barthe, Loïc; Paulin, Mathias; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a new real-time soft shadow algorithm using a single shadow map per light source. Therefore, our algorithm is well suited to render both complex and dynamic scenes, and it handles all rasterizable geometries. The key idea of our method is to use the shadow map as a simple and uniform discretized represention of the scene, thus allowing us to generate realistic soft shadows in most cases. In particular it naturally handles occluder fusion. Also, our algorithm deals with rectangular light sources as well as textured light sources with high precision, and it maps well to programmable graphics hardware.Item Surface Enhancement Using Real-time Photometric Stereo and Reflectance Transformation(The Eurographics Association, 2006) Malzbender, Tom; Wilburn, Bennett; Gelb, Dan; Ambrisco, Bill; Tomas Akenine-Moeller and Wolfgang HeidrichPhotometric stereo recovers per-pixel estimates of surface orientation from images of a surface under varying lighting conditions. Transforming reflectance based on recovered normal directions is useful for enhancing the appearance of subtle surface detail. We present the first system that achieves real-time photometric stereo and reflectance transformation. A high-speed video camera, computer controlled light sources and fast GPU implementations of the algorithms enable both methods. We also present novel GPU-accelerated normal transformations before relighting that "amplify" shape detail. By applying standard image processing methods to our computed normal image, we can selectively enhance surface detail at different frequencies. Our system allows users in fields such as forensics, archeology and dermatology to investigate objects and surfaces by simply holding them in front of the camera. Real-time analysis of surface roughness for metrology can also be performed from the extracted normal field.Item Symmetric Photography: Exploiting Data-sparseness in Reflectance Fields(The Eurographics Association, 2006) Garg, Gaurav; Talvala, Eino-Ville; Levoy, Marc; Lensch, Hendrik P. A.; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a novel technique called symmetric photography to capture real world reflectance fields. The technique models the 8D reflectance field as a transport matrix between the 4D incident light field and the 4D exitant light field. It is a challenging task to acquire this transport matrix due to its large size. Fortunately, the transport matrix is symmetric and often data-sparse. Symmetry enables us to measure the light transport from two sides simultaneously, from the illumination directions and the view directions. Data-sparseness refers to the fact that sub-blocks of the matrix can be well approximated using low-rank representations. We introduce the use of hierarchical tensors as the underlying data structure to capture this data-sparseness, specifically through local rank-1 factorizations of the transport matrix. Besides providing an efficient representation for storage, it enables fast acquisition of the approximated transport matrix and fast rendering of images from the captured matrix. Our prototype acquisition system consists of an array of mirrors and a pair of coaxial projector and camera.We demonstrate the effectiveness of our system with scenes rendered from reflectance fields that were captured by our system. In these renderings we can change the viewpoint as well as relight using arbitrary incident light fields.Item Spatio-Angular Resolution Tradeoffs in Integral Photography(The Eurographics Association, 2006) Georgeiv, Todor; Zheng, Ke Colin; Curless, Brian; Salesin, David; Nayar, Shree; Intwala, Chintan; Tomas Akenine-Moeller and Wolfgang HeidrichAn integral camera samples the 4D light field of a scene within a single photograph. This paper explores the fundamental tradeoff between spatial resolution and angular resolution that is inherent to integral photography. Based on our analysis we divide previous integral camera designs into two classes depending on how the 4D light field is distributed (multiplexed) over the 2D sensor. Our optical treatment is mathematically rigorous and extensible to the broader area of light field research. We argue that for many real-world scenes it is beneficial to sacrifice angular resolution for higher spatial resolution. The missing angular resolution is then interpolated using techniques from computer vision. We have developed a prototype integral camera that uses a system of lenses and prisms as an external attachment to a conventional camera. We have used this prototype to capture the light fields of a variety of scenes. We show examples of novel view synthesis and refocusing where the spatial resolution is significantly higher than is possible with previous designs.Item Feature-Aware Texturing(The Eurographics Association, 2006) Gal, Ran; Sorkine, Olga; Cohen-Or, Daniel; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a method for inhomogeneous 2D texture mapping guided by a feature mask, that preserves some regions of the image, such as foreground objects or other prominent parts. The method is able to arbitrarily warp a given image while preserving the shape of its features by constraining their deformation to be a similarity transformation. In particular, our method allows global or local changes to the aspect ratio of the texture without causing undesirable shearing to the features. The algorithmic core of our method is a particular formulation of the Laplacian editing technique, suited to accommodate similarity constraints on parts of the domain. The method is useful in digital imaging, texture design and any other applications involving image warping, where parts of the image have high familiarity and should retain their shape after modification.Item Texture Transfer Using Geometry Correlation(The Eurographics Association, 2006) Mertens, Tom; Kautz, Jan; Chen, Jiawen; Bekaert, Philippe; Durand, Frédo; Tomas Akenine-Moeller and Wolfgang HeidrichTexture variation on real-world objects often correlates with underlying geometric characteristics and creates a visually rich appearance. We present a technique to transfer such geometry-dependent texture variation from an example textured model to new geometry in a visually consistent way. It captures the correlation between a set of geometric features, such as curvature, and the observed diffuse texture. We perform dimensionality reduction on the overcomplete feature set which yields a compact guidance field that is used to drive a spatially varying texture synthesis model. In addition, we introduce a method to enrich the guidance field when the target geometry strongly differs from the example. Our method transfers elaborate texture variation that follows geometric features, which gives 3D models a compelling photorealistic appearance.Item Silhouette Texture(The Eurographics Association, 2006) Wu, Hongzhi; Wei, Li-Yi; Wang, Xi; Guo, Baining; Tomas Akenine-Moeller and Wolfgang HeidrichUsing coarse meshes with textures and/or normal maps to represent detailed meshes often results in poor visual quality along silhouettes. To tackle this problem, we introduce silhouette texture, a new data structure for capturing and reconstructing the silhouettes of detailed meshes. In addition to the recording of color and normal fields in traditional methods, we sample information that represents the original silhouettes and pack it into a three dimensional texture. In the rendering stage, our algorithm extracts relevant information from the texture to rebuild the silhouettes for any perspective view. Unlike previous work, our approach is based on GPU and could achieve high rendering performance. Moreover, both exterior and interior silhouettes are processed for better approximation quality. In addition to rendering acceleration, our algorithm also enables detailed silhouette visualization with minimum geometric complexity.Item Texture Replacement of Garments in Monocular Video(The Eurographics Association, 2006) Scholz, Volker; Magnor, Marcus; Tomas Akenine-Moeller and Wolfgang HeidrichIn this paper, we present a video processing algorithm for texture replacement of moving garments in monocular video recordings. We use a color-coded pattern which encodes texture coordinates within a local neighborhood in order to determine the geometric deformation of the texture. A time-coherent texture interpolation is obtained by the use of 3D radial basis functions. Shading maps are determined with a surface reconstruction technique and applied to new textures which replace the color pattern in the video sequence. Our method enables exchanging fabric pattern designs of garments worn by actors as a video post-processing step.Item A GPU-driven Algorithm for Accurate Interactive Reflections on Curved Objects(The Eurographics Association, 2006) Estalella, Pau; Martin, Ignacio; Drettakis, George; Tost, Dani; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a GPU-driven method for the fast computation of specular reflections on curved objects. For every reflector of the scene, our method computes a virtual object for every other object reflected in it. This virtual reflected object is then rendered and blended with the scene. For each vertex of each virtual object, a reflection point is found on the reflector s surface. This point is used to find the reflected virtual vertex, enabling the reflected virtual scene to be rendered. Our method renders the 3D points and normals of the reflector into textures, and uses a local search in a fragment program on the GPU to find the reflection points. By reorganizing the data and the computation in this manner, and correctly treating special cases, we make excellent use of the parallelism and stream-processing power of the GPU. In our results we show that, with our method, we can display high-quality reflections of nearby objects interactively.Item A Novel Method for Fast and High-Quality Rendering of Hair(The Eurographics Association, 2006) Xu, Songhua; Lau, Francis C. M.; Jiang, Hao; Pan, Yunhe; Tomas Akenine-Moeller and Wolfgang HeidrichThis paper proposes a new rendering approach for hair. The model we use incorporates semantics-related information directly in the appearance modeling function which we call a Semantics-Aware Texture Function (SATF). This new appearance modeling function is well suited for constructing an off-line/on-line hybrid algorithm to achieve fast and high-quality rendering of hair. The off-line phase generates intermediate results in a database for sample geometries under different viewing and lighting conditions, which can be used to complete a large part of the overall computation and leaves only a few dynamic tasks to be performed on-line. We propose a model having four levels, from the whole hair volume to the very fine hair density level. We further employ an efficient disk-like structure to represent hair distributions inside a hair cluster. As the intermediate database carries opacity information, self-shadows can be easily generated. We present experiment results which clearly show that our methodology can indeed produce high quality rendering results efficiently. Supplementary materials and supporting demos can be found in our project website http://www.cs.hku.hk/~songhua/hair-rendering/.Item Interactive Screen-Space Accurate Photon Tracing on GPUs(The Eurographics Association, 2006) Krüger, Jens; Bürger, Kai; Westermann, Rüdiger; Tomas Akenine-Moeller and Wolfgang HeidrichRecent advances in algorithms and graphics hardware have opened the possibility to render caustics at interactive rates on commodity PCs. This paper extends on this work in that it presents a new method to directly render caustics on complex objects, to compute one or several refractions at such objects and to simulate caustics shadowing. At the core of our method is the idea to avoid the construction of photon maps by tracing photons in screen-space on programmable graphics hardware. Our algorithm is based on the rasterization of photon paths into texture maps. Intersection events are then resolved on a per-fragment basis using layered depth images. To correctly spread photon energy in screen-space we render aligned point sprites at the diffuse receivers where photons terminate. As our method does neither require any pre-processing nor an intermediate radiance representation it can efficiently deal with dynamic scenery and scenery that is modified, or even created on the GPU.Item Ambient Occlusion for Animated Characters(The Eurographics Association, 2006) Kontkanen, Janne; Aila, Timo; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a novel technique for approximating ambient occlusion of animated objects. Our method automatically determines the correspondence between animation parameters and per-vertex ambient occlusion using a set of reference poses as its input. Then, at runtime, the ambient occlusion is approximated by taking a dot product between the current animation parameters and static per-vertex coefficients. According to our results, both the computational and storage requirements are low enough for the technique to be directly applicable to computer games running on current graphics hardware. The resulting images are also significantly more realistic than the commonly used static ambient occlusion solutions.Item Ardeco: Automatic Region DEtection and COnversion(The Eurographics Association, 2006) Lecot, Gregory; Levy, Bruno; Tomas Akenine-Moeller and Wolfgang HeidrichWe present Ardeco, a new algorithm for image abstraction and conversion from bitmap images into vector graphics. Given a bitmap image, our algorithm automatically computes the set of vector primitives and gradients that best approximates the image. In addition, more details can be generated in user-selected important regions, defined from eye-tracking data or from an importance map painted by the user. Our algorithm is based on a new two-level variational parametric segmentation algorithm, minimizing Mumford and Shah s energy and operating on an intermediate triangulation, well adapted to the features of the image.Item Segmentation-Based 3D Artistic Rendering(The Eurographics Association, 2006) Kolliopoulos, Alexander; Wang, Jack M.; Hertzmann, Aaron; Tomas Akenine-Moeller and Wolfgang HeidrichThis paper introduces segmentation-based 3D non-photorealistic rendering, in which 3D scenes are rendered as a collection of 2D image segments. Segments abstract out unnecessary detail and provide a basis for defining new rendering styles. These segments are computed by a spectral clustering algorithm that incorporates 3D information, including depth, user-defined importance, and object grouping. Temporally coherent animation is created by biasing adjacent frames to have similar segmentations. We describe algorithms for rendering segments in styles inspired by a number of hand-painted images.Item Bidirectional Instant Radiosity(The Eurographics Association, 2006) Segovia, Benjamin; Iehl, Jean Claude; Mitanchey, Richard; Péroche, Bernard; Tomas Akenine-Moeller and Wolfgang HeidrichThis paper presents a new sampling strategy to achieve interactive global illumination on one commodity computer. The goal is to propose an efficient numerical stochastic scheme which can be well adapted to a fast rendering algorithm. As we want to provide an efficient sampling strategy to handle difficult settings without sacrificing performance in common cases, we developed an extension of Instant Radiosity [Kel97] in the same way bidirectional path tracing is an extension of path or light tracing. Our idea is to build several estimators and to efficiently combine them to find a set of virtual point light sources which are relevant for the areas of the scene seen by the camera. The resulting algorithm is faster than classical solutions to global illumination. Using today graphics hardware, an interactive frame rate and the convergence of the scheme can be easily obtained in scenes with many light sources, glossy materials or difficult visibility problems.Item Painting With Texture(The Eurographics Association, 2006) Ritter, Lincoln; Li, Wilmot; Curless, Brian; Agrawala, Maneesh; Salesin, David; Tomas Akenine-Moeller and Wolfgang HeidrichWe present an interactive texture painting system that allows the user to author digital images by painting with a palette of input textures. At the core of our system is an interactive texture synthesis algorithm that generates textures with natural-looking boundary effects and alpha information as the user paints. Furthermore, we describe an intuitive layered painting model that allows strokes of texture to be merged, intersected and overlapped while maintaining the appropriate boundaries between texture regions. We demonstrate the utility and expressiveness of our system by painting several images using textures that exhibit a range of different boundary effects.Item Directing Gaze in 3D Models with Stylized Focus(The Eurographics Association, 2006) Cole, Forrester; DeCarlo, Doug; Finkelstein, Adam; Kin, Kenrick; Morley, Keith; Santella, Anthony; Tomas Akenine-Moeller and Wolfgang HeidrichWe present an interactive system for placing emphasis in stylized renderings of 3D models. The artist chooses a camera position, an area of interest, and a rendering style for the scene. The system then automatically renders the scene with emphasis in the area of interest, an effect we call "stylized focus." Stylized focus draws the viewer s gaze to the emphasized area, through local variations in shading effects such as color saturation and contrast as well as line qualities such as texture and density. We introduce a novel algorithm for local control of line density that exhibits a degree of temporal coherence suitable for animation. Animating the area of emphasis produces an effect we call the "stylized focus pull." Finally, an eye-tracking experiment verifies that the emphasis does indeed draw the viewer s gaze to the area of interest.Item A Spectral BSSRDF for Shading Human Skin(The Eurographics Association, 2006) Donner, Craig; Jensen, Henrik Wann; Tomas Akenine-Moeller and Wolfgang HeidrichWe present a novel spectral shading model for human skin. Our model accounts for both subsurface and surface scattering, and uses only four parameters to simulate the interaction of light with human skin. The four parameters control the amount of oil, melanin and hemoglobin in the skin, which makes it possible to match specific skin types. Using these parameters we generate custom wavelength dependent diffusion profiles for a two-layer skin model that account for subsurface scattering within the skin. These diffusion profiles are computed using convolved diffusion multipoles, enabling an accurate and rapid simulation of the subsurface scattering of light within skin. We combine the subsurface scattering simulation with a Torrance-Sparrow BRDF model to simulate the interaction of light with an oily layer at the surface of the skin. Our results demonstrate that this four parameter model makes it possible to simulate the range of natural appearance of human skin including African, Asian, and Caucasian skin types.Item Image-driven Navigation of Analytical BRDF Models(The Eurographics Association, 2006) Ngan, Addy; Durand, Frédo; Matusik, Wojciech; Tomas Akenine-Moeller and Wolfgang HeidrichSpecifying parameters of analytic BRDF models is a difficult task as these parameters are often not intuitive for artists and their effect on appearance can be non-uniform. Ideally, a given step in the parameter space should produce a predictable and perceptually-uniform change in the rendered image. Systems that employ psychophysics have produced important advances in this direction; however, the requirement of user studies limits scalability of these approaches. In this work, we propose a new and intuitive method for designing material appearance. First, we define a computational metric between BRDFs that is based on rendered images of a scene under natural illumination. We show that our metric produces results that agree with previous perceptual studies. Next, we propose a user interface that allows for navigation in the remapped parameter space of a given BRDF model. For the current settings of the BRDF parameters, we display a choice of variations corresponding to uniform steps according to our metric, in the various parameter directions. In addition to the parametric navigation for a single model, we also support neighborhood navigation in the space of all models. By clustering a large number of neighbors and removing neighbors that are close to the current model, the user can easily visualize the alternate effects that can only be expressed with other models. We show that our interface is simple and intuitive. Furthermore, visual navigation in the BRDF space both in the local model and the union space is an effective way for reflectance design.