Real-Time Volumetric TestsUsing Layered Depth Ima

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Published on July 15, 2008

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Slide 1: Real-Time Volumetric TestsUsing Layered Depth Images Hasso-Plattner Institute,University of Potsdam, Germany Matthias Trapp, Jürgen Döllner Outline : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 2 Outline Introduction Layered Depth Images on GPU Volumetric Parity Test Discussion Conclusion Introduction : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 3 Introduction Volumetric Test… …determines if a 3D point is inside or outside a given volume Areas of application: Generalized clipping, Rendering with hybrid styles, GPU collision detection,… Characteristics: Performed in shader program Real-time Real-Time Volumetric Tests : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 4 Real-Time Volumetric Tests Ingredients: data structure + algorithm Volume representation of polygonal shapes Hardware accelerated data structure Gives a sufficient approximation  Layered Depth Image Volumetric test for 3D points Applicable in shader programs, Fast and efficient implementation  Volumetric Parity Test Layer Depth Images on GPU : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 5 Layer Depth Images on GPU Layered Depth Images (LDI)[Shade et al. 1998] GPU representation of LDIs: Depth maps = layers of unique depth complexity 3D texture or 2D texture array of depth maps Texture format: 32bit floating point LDI Example : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 6 LDI Example Depth-Peeling to 3D Texture : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 7 Depth-Peeling to 3D Texture Scale shape into unit volume Set orthographic projection, adjust near/far planes Determine depth complexity of shape Create and initialize 3D texture (LDI) Depth-peel polygonal shape [Everitt 2001] Multipass render-to-texture (to slice of 3D texture) Use linear depth-buffer values [Lapidious et al. 1999] GLSL fragment shader for 2nd depth test (SM4) Volumetric Parity Test (VPT) : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 8 Volumetric Parity Test (VPT) “to determine if a point is inside or outside a complex 3D volume represented by an LDI” Given: arbitrary 3D point: Requested: Boolean parity: Solution: Transformation into LDI texture space: Perform ray-marching through depth maps Ray-Marching in LDI Texture Space : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 9 Ray-Marching in LDI Texture Space Construct a ray Sample from each slice Compare depth values Efficient Shader Implementation : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 10 Efficient Shader Implementation Discussion : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 11 Discussion Limitations: Memory consumptions Depth-peeling costs Limited number of LDI Drawbacks: Under sampling artifacts Aliasing artifacts VPT is fill-limited Conclusion & Future Work : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 12 Conclusion & Future Work Take away: Volumetric test in real-time Based on LDI Different applications Sampling artifacts Future work: LDI compression Optimal viewpoint selection Solve sampling artifacts Ray-LDI intersection test Slide 13: EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 13 Thank You. Matthias Trapp matthias.trapp@hpi.uni-potsdam.de Computer Graphics Systems Group Prof. Dr. Jürgen Döllner www.hpi.uni-potsdam.de/3d Researchgroup 3D-Geoinformation www.3dgi.de Main References : EG 2008 :: 17th April Real-Time Volumetric Tests Using Layered Depth Images :: Matthias Trapp 14 Main References [Shade 1998] SHADE J., GORTLER S., WEI HE L., SZELISKI R.: Layered Depth Images. In SIGGRAPH ’98 (New York, NY, USA, 1998), ACM, pp. 231–242. [Everitt 2001] CASS EVERITT: Interactive Order-Independent Transparency. Tech. rep., NVIDIA Corporation, 2001. [Lapidous 1999]LAPIDOUS E., JIAO G.: Optimal Depth Buffer for Low-Cost Graphics Hardware. In HWWS ’99 (New York, NY, USA, 1999), ACM, pp. 67–73.

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