| 1. |
- Moreau, Pierre, et al.
(författare)
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Photon Splatting Using a View-Sample Cluster Hierarchy
- 2016
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Ingår i: High-Performance Graphics 2016. - 2079-8679. - 9783038680086
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Konferensbidrag (refereegranskat)abstract
- Splatting photons onto primary view samples, rather than gathering from a photon acceleration structure, can be a more efficient approach to evaluating the photon-density estimate in interactive applications, where the number of photons is often low compared to the number of view samples. Most photon splatting approaches struggle with large photon radii or high resolutions due to overdraw and insufficient culling. In this paper, we show how dynamic real-time diffuse interreflection can be achieved by using a full 3D acceleration structure built over the view samples and then splatting photons onto the view samples by traversing this data structure. Full dynamic lighting and scenes are possible by tracing and splatting photons, and rebuilding the acceleration structure every frame. We show that the number of view-sample/photon tests can be significantly reduced and suggest further culling techniques based on the normal cone of each node in the hierarchy. Finally, we present an approximate variant of our algorithm where photon traversal is stopped at a fixed level of our hierarchy, and the incoming radiance is accumulated per node and direction, rather than per view sample. This improves performance significantly with little visible degradation of quality.
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| 2. |
- Akenine-Möller, Tomas, et al.
(författare)
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Approximate Soft Shadows on Arbitrary Surfaces using Penumbra Wedges
- 2002
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Ingår i: EGRW '02 Proceedings of the 13th Eurographics workshop on Rendering. - 1581135343 ; , s. 297-306
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Konferensbidrag (refereegranskat)abstract
- Shadow generation has been subject to serious investigation in computer graphics, and many clever algorithms have been suggested. However, previous algorithms cannot render high quality soft shadows onto arbitrary, animated objects in real time. Pursuing this goal, we present a new soft shadow algorithm that extends the standard shadow volume algorithm by replacing each shadow quadrilateral with a new primitive, called the penumbra wedge. For each silhouette edge as seen from the light source, a penumbra wedge is created that approximately models the penumbra volume that this edge gives rise to. Together the penumbra wedges can render images that often are remarkably close to more precisely rendered soft shadows. Furthermore, our new primitive is designed so that it can be rasterized efficiently. Many real-time algorithms can only use planes as shadow receivers, while ours can handle arbitrary shadow receivers. The proposed algorithm can be of great value to, e.g., 3D computer games, especially since it is highly likely that this algorithm can be implemented on programmable graphics hardware coming out within the next year, and because games often prefer perceptually convincing shadows.
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| 3. |
- Akenine-Möller, Tomas, et al.
(författare)
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On the Degree of Vertices in a Shadow Volume Silhouette
- 2003
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Ingår i: Journal of Graphics Tools. - : Informa UK Limited. - 1086-7651 .- 2151-237X. ; 8:4, s. 21-24
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Tidskriftsartikel (refereegranskat)abstract
- In shadow volume rendering, the shadow volume silhouette edges are used to create primitives that model the shadow volume. A common misconception is that the vertices on such silhouettes can only be connected to two silhouette edges, i.e., have degree two. Furthermore, some believe that such a vertex can have any degree. In this short note, we present a geometric proof that shows that the degree of a silhouette vertex must be even, and not necessarily two.
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| 4. |
- Assarsson, Ulf, 1972, et al.
(författare)
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A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware
- 2003
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Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 22:3, s. 511-520
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Konferensbidrag (refereegranskat)abstract
- Most previous soft shadow algorithms have either suffered from aliasing, been too slow, or could only use a limited set of shadow casters and/or receivers. Therefore, we present a strengthened soft shadow volume algorithm that deals with these problems. Our critical improvements include robust penumbra wedge construction, geometry-based visibility computation, and also simplified computation through a four-dimensional texture lookup. This enables us to implement the algorithm using programmable graphics hardware, and it results in images that most often are indistinguishable from images created as the average of 1024 hard shadow images. Furthermore, our algorithm can use both arbitrary shadow casters and receivers. Also, one version of our algorithm completely avoids sampling artifacts which is rare for soft shadow algorithms. As a bonus, the four-dimensional texture lookup allows for small textured light sources, and, even video textures can be used as light sources. Our algorithm has been implemented in pure software, and also using the GeForce FX emulator with pixel shaders. Our software implementation renders soft shadows at 0.5-5 frames per second for the images in this paper. With actual hardware, we expect that our algorithm will render soft shadows in real time. An important performance measure is bandwidth usage. For the same image quality, an algorithm using the accumulated hard shadow images uses almost two orders of magnitude more bandwidth than our algorithm.
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| 5. |
- Assarsson, Ulf, 1972
(författare)
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A Real-Time Soft Shadow Volume Algorithm
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rendering of shadows is a very important ingredient in three-dimensional graphics since they increase the level of realism and provide cues to spatial relationships. Area or volumetric light sources give rise to so called soft shadows, i.e., there is a smooth transition from no shadow to full shadow. For hard shadows, which are generated by point light sources, the transition is abrupt. Since all real light sources occupy an area or volume, soft shadows are more realistic than hard shadows. Fast rendering of soft shadows, preferably in real time, has been a subject for research for decades, but so far this has mostly been an unsolved problem. Therefore, this thesis, which is based on five papers, focuses on how to achieve real-time rendering of soft shadows. The first four papers constitute the foundation and evolution of a new algorithm, called the soft shadow volume algorithm, and the fifth paper provides an essential proof for correctness and generality of this and some previous shadow algorithms. The algorithm augments and extends the well-known shadow volume algorithm for hard shadows. Two passes are used, where the first pass consist of the classic shadow volume algorithm to generate the hard shadows (umbra). The second pass compensates to provide the softness (penumbra). This is done by generating penumbra wedges and rasterizing them using a custom pixel shader that for each rasterized pixel projects the hard shadow quadrilaterals onto the light source and computes the covered area. A result of the thesis is an algorithm capable of real-time soft shadows that utilizes programmable graphics hardware. The algorithm produce high-quality shadows for area light sources and volumetric light sources. It also handles textured light sources, which currently is a very rare capability among real-time soft shadow algorithms. Even video textures are allowed as light sources.
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| 6. |
- Assarsson, Ulf, 1972, et al.
(författare)
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An Optimized Soft Shadow Volume Algorithm with Real-Time Performance
- 2003
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Ingår i: Proceedings of the SIGGRAPH/ Eurographics Workshop on Graphics Hardware, San Diego, 26-27 July 2003. - 9781581137392 ; , s. 33-40
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present several optimizations to our previously presented soft shadow volume algorithm. Our optimizations include tighter wedges, heavily optimized pixel shader code for both rectangular and spherical light sources, a frame buffer blending technique to overcome the limitation of 8-bit frame buffers, and a simple culling algorithm. These together give real-time performance, and for simple models we get frame rates of over 150 fps. For morecomplex models 50 fps is normal. In addition to optimizations, two simple techniques for improving the visual quality are also presented.
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| 7. |
- Assarsson, Ulf, 1972, et al.
(författare)
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Image-Space Dynamic Transparency for Improved Object Discovery in 3D Environments
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present an image-space algorithm for dynamic transparency with the purpose of supporting object discovery and access in information-rich 3D visualization environments. The algorithm is based on multiple rendering passes and detects instances of object occlusion in the image-space using the fragment shader capabilities of modern programmable graphics hardware, creating alpha maps of opacity gradients around the occluded objects. In essence, the effect is somewhat similar to X-ray vision of a superhero. We have implemented a prototype version of our algorithm with real-time rendering performance using a number of optimizations and speedups on current graphics hardware. To evaluate its use, we have also implemented three different example applications portraying different scenarios, including abstract visualization, virtual walkthrough, and gaming. Preliminary results from an empirical user study comparing our technique to standard viewpoint controls indicate that our technique is superior in regards to object discovery efficiency. These results hold over both completion times as well as correctness of a visual search task.
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| 8. |
- Assarsson, Ulf, 1972, et al.
(författare)
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Occlusion Culling and Z-fail for Soft Shadow Volume Algorithms
- 2004
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Ingår i: Visual Computer. - : Springer Science and Business Media LLC. - 0178-2789 .- 1432-2315. ; 20:8-9, s. 601-612
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a significant improvement of our previously proposed soft shadow volume algorithm for simulating soft shadows. By restructuring the algorithm, we can considerably simplify the computations, introduce efficient occlusion culling with speedups of 3-4 times, thus approaching real-time performance. We can also generalize the algorithm to produce correct shadows even when the eye is inside a shadowed region (using z-fail). We present and evaluate a three pass implementation of the restructured algorithm for near real-time rendering of soft shadows on a computer with a commodity graphics accelerator. However, preferably the rendering of the wedges should be implemented in hardware, and for this we suggest and evaluate a single pass algorithm.
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| 9. |
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| 10. |
- Billeter, Markus, 1984, et al.
(författare)
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Efficient stream compaction on wide SIMD many-core architectures
- 2009
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Ingår i: Proceedings of the Conference on High Performance Graphics. - 9781605586038 ; 2009, s. 159-166
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Konferensbidrag (refereegranskat)abstract
- Stream compaction is a common parallel primitive used to remove unwanted elements in sparse data. This allows highly parallel algorithms to maintain performance over several processing steps and reduces overall memory usage.For wide SIMD many-core architectures, we present a novel stream compaction algorithm and explore several variations thereof. Our algorithm is designed to maximize concurrent execution, with minimal use of synchronization. Bandwidth and auxiliary storage requirements are reduced significantly, which allows for substantially better performance.We have tested our algorithms using CUDA on a PC with an NVIDIA GeForce GTX280 GPU. On this hardware, our reference implementation provides a 3x speedup over previous published algorithms.
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