Real-Time Volumetric Tests Using Layered Depth Images Hasso-Plattner Institute, University of Potsdam, Germany Matthias Tr...
Outline <ul><li>Introduction  </li></ul><ul><li>Layered Depth Images on GPU </li></ul><ul><li>Volumetric Parity Test </li>...
Introduction <ul><li>Volumetric Test… </li></ul><ul><li>… determines if a 3D point </li></ul><ul><li>is inside or outside ...
Real-Time Volumetric Tests <ul><li>Ingredients: data structure + algorithm </li></ul><ul><li>Volume representation  of pol...
Layer Depth Images on GPU <ul><li>Layered Depth Images (LDI) [ Shade et al. 1998 ] </li></ul><ul><li>GPU representation of...
LDI Example
Depth-Peeling to 3D Texture <ul><li>Scale shape into unit volume </li></ul><ul><li>Set  orthographic  projection, adjust n...
Volumetric Parity Test (VPT) <ul><li>“ to determine if a point is  inside  or  outside </li></ul><ul><li>a complex 3D volu...
Ray-Marching in LDI Texture Space <ul><li>Construct a ray </li></ul><ul><li>Sample from each slice </li></ul><ul><li>Compa...
Efficient Shader Implementation
Discussion <ul><li>Limitations: </li></ul><ul><li>Memory consumptions </li></ul><ul><li>Depth-peeling costs </li></ul><ul>...
Conclusion & Future Work <ul><li>Take away: </li></ul><ul><li>Volumetric test in real-time </li></ul><ul><li>Based on LDI ...
<ul><li>Thank You. </li></ul><ul><li>Matthias Trapp </li></ul><ul><li>[email_address] </li></ul><ul><li>Computer Graphics ...
Main References <ul><li>[ Shade 1998 ] </li></ul><ul><li>SHADE J., GORTLER S., WEI HE L., SZELISKI R.:  Layered Depth Imag...
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Real-Time Volumetric Tests (EG 2008)

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Real-Time Volumetric Tests (EG 2008)

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

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