VMV15

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https://diglib.eg.org/handle/10.2312/13268

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Browsing VMV15 by Subject "I.3.7 [Computer Graphics]"

Now showing 1 - 5 of 5
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    The Bounced Z-buffer for Indirect Visibility
    (The Eurographics Association, 2015) Nalbach, Oliver; Ritschel, Tobias; Seidel, Hans-Peter; David Bommes and Tobias Ritschel and Thomas Schultz
    Synthesizing images of animated scenes with indirect illumination and glossy materials at interactive frame rates commonly ignores indirect shadows. In this work we extend a class of indirect lighting algorithms that splat shading to a framebuffer - we demonstrate deep screen space and ambient occlusion volumes - to include indirect visibility. To this end we propose the bounced z-buffer: While a common z-buffered framebuffer, at each pixel, maintains the distance from the closest surface and its radiance along a direction from the camera to that pixel, our new representation contains the distance from the closest surface and its radiance after one indirect bounce into a certain other direction. Consequently, with bounced z-buffering, only the splat from the nearest emitter in one direction contributes to each pixel. Importance-sampling the bounced directions according to the product of cosine term and BRDF allows to approximate full shading by a simple sum of neighboring framebuffer pixels.
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    Extrapolating Large-Scale Material BTFs under Cross-Device Constraints
    (The Eurographics Association, 2015) Steinhausen, Heinz Christian; Brok, Dennis den; Hullin, Matthias B.; Klein, Reinhard; David Bommes and Tobias Ritschel and Thomas Schultz
    In this paper, we address the problem of acquiring bidirectional texture functions (BTFs) of large-scale material samples. Our approach fuses gonioreflectometric measurements of small samples with few constraint images taken on a flatbed scanner under semi-controlled conditions. Underlying our method is a lightweight texture synthesis scheme using a local texture descriptor that combines shading and albedo across devices. Since it operates directly on SVD-compressed BTF data, our method is computationally efficient and can be implemented on a moderate memory footprint.
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    Level-of-Detail for Production-Scale Path Tracing
    (The Eurographics Association, 2015) Prus, Magdalena; Eisenacher, Christian; Stamminger, Marc; David Bommes and Tobias Ritschel and Thomas Schultz
    Path-traced global illumination (GI) becomes increasingly important in movie production. With offscreen elements considerably contributing to the path traced image, geometric complexity increases drastically, requiring geometric instancing or a variety of manually created and baked LOD. To reduce artists' work load and bridge the gap between mesh-based LOD (Mip-maps) and voxel-based LOD (brickmaps), we propose to use an SVO with averaged BRDF parameters, e.g. for the Disney-BRDF, and a normal distribution per voxel. During shading we construct a BRDF from the averaged BRDF parameters and evaluate it with a random normal sampled from the distribution. This is simple, memory-efficient, and handles a wide variety of geometry scales and materials seamlessly, with proper filtering. Further it is efficient to construct, which allows quick artist iterations as well as automatic and lazy generation on scene loading.
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    Rotoscoping on Stereoscopic Images and Videos
    (The Eurographics Association, 2015) Bukenberger, Dennis R.; Schwarz, Katharina; Groh, Fabian; Lensch, Hendrik P. A.; David Bommes and Tobias Ritschel and Thomas Schultz
    Creating an animation based on video footage (rotoscoping) often requires significant manual work. For monoscopic videos diverse publications already feature (semi-)automatic techniques to apply non-photorealistic image abstraction (NPR) to videos. This paper addresses abstraction of 3D stereo content minimizing stereoscopic discomfort in images and videos. We introduce a completely autonomous framework that enhances stereo and temporal consistency. Stereoscopic coherence with consistent textures for both eyes is produced by warping the left and right images into a central disparity domain followed by mapping them back to the left and right view. Smooth movements with reduced flickering are achieved by considering optical flow in the propagation of abstract features between frames. The results show significant improvements of stereo consistency without discomforting artifacts in the depth perception. We extend existing stroke based rendering (SBR) for higher accuracy at strong image gradients. Furthermore, we demonstrate that our stereo framework is easily applicable to other point-based abstraction styles. Finally, we evaluate the stereo consistency of our results in a small user study and show that the comfort of the visual appearance is maintained.
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    Vector-to-Closest-Point Octree for Surface Ray-Casting
    (The Eurographics Association, 2015) Demir, Ismail; Westermann, Rüdiger; David Bommes and Tobias Ritschel and Thomas Schultz
    GPU voxel-based surface ray-casting has positioned as an interesting alternative to rasterization-based rendering approaches, because it allows using many processing units simultaneously, can effectively exploit thread level parallelism, and enables fine-granularity occlusion culling on the pixel level. Yet voxel-based techniques face the problem that an extremely high resolution is necessary to avoid block artifacts at high zoom levels. In this work, we propose a novel improvement of voxel-based ray-casting to overcome this limitation. By using a hierarchical Vector-to-Closest-Point (VCP) representation, we can inherit the advantages of a voxel-based approach at a much smoother approximation of the surface. We demonstrate that, although the VCP grid consumes more memory per cell, it requires less memory overall, because it builds upon a significantly shallower tree hierarchy. In a number of examples we demonstrate the use of our approach for high-quality rendering of high resolution surface models.