1. A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware Speaker: Alvin Date:2003/7/23 SIGGRAPH 2003 Ulf Assarsson Tomas Akenine-Moller

2. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 2 Outline Introduction Introduction Constrain Constrain Frame Work Frame Work Conclusion Conclusion

3. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 3 Introduction Umbra & Penumbra. Umbra & Penumbra. Penumbra Wedge & Penumbra Volume. Penumbra Wedge & Penumbra Volume.

4. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 4 Constrain Only use the silhouette edges as seen from the center of the light source. Only use the silhouette edges as seen from the center of the light source. Only compute the union Only compute the union of the shadows of the objects but not the shadow of the union of the objects.

5. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 5 Frame Work Construction the Penumbra Wedges. Construction the Penumbra Wedges. Construction the Penumbra Wedges. Construction the Penumbra Wedges. Visibility Computation. Visibility Computation. Visibility Computation. Visibility Computation. Compute the hard shadow quad. Compute the hard shadow quad. Compensate for the overstatement. Compensate for the overstatement. Rendering. Rendering. Rendering.

6. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 6 Conclusion The result is indistinguishable from images rendered using the average of 1024 hard shadow images. The result is indistinguishable from images rendered using the average of 1024 hard shadow images. Suitable for arbitrary shadow casting and shadow receiving objects. Suitable for arbitrary shadow casting and shadow receiving objects. It can handle light sources with texture. It can handle light sources with texture. Use the hardware to render soft shadow in real time. Use the hardware to render soft shadow in real time.

7. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 7 Thank you for your attention.

8. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 8 Construction of Penumbra Wedges

9. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 9 Visibility Computation V-buffer V-buffer If value == 1.0 -> In umbra region. If value == 1.0 -> In umbra region. If value == 0.0 -> Outside any shadow region. If value == 0.0 -> Outside any shadow region. Otherwise -> In penumbra region. Otherwise -> In penumbra region. Initially the V-buffer is cleared to 1.0. Initially the V-buffer is cleared to 1.0.

10. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 10 Visibility Pass 1

11. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 11 Visibility Pass 2

12. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 12 Visibility Pass 2 Use the 4-tuple (x1,y1,x2,y2) as an index into the 4D texture. Use the 4-tuple (x1,y1,x2,y2) as an index into the 4D texture. Use the quadlinear filtering to improve smoothness. Use the quadlinear filtering to improve smoothness. The texture is precomputed. (So it can use textures to be the light sources.) The texture is precomputed. (So it can use textures to be the light sources.) The output of the query is the coverage. The output of the query is the coverage.

13. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 13 Example

14. Alivn/GAME LAB/CSIE/NDHU A Geometry-based Soft Shadow Volume Algorithm using Graphics Hardware 14 Rendering