Shadow Volumes on Programmable Graphics Hardware Speaker: Alvin Date: 2003/11/3 EUROGRAPHICS 2003

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware2 Outline  Motivation  Silhouette Detection  Generation of Shadow Volumes  Implementation  Result  Conclusion & Future Work

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware3 Motivation  Consistent precision.  Objects can be used with vertex shader.  Gain more CPU time.  No longer needs to synchronize.  Silhouette extraction is speed up.  Becomes very simple.

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware4 Silhouette Detection Input Mesh

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware5 Generation of Shadow Volumes  Each vertex has a total of three indices and one flag. –Two indices referring to the world space coordinates of the edge’s two end points. –One index referring to the silhouette flag and the vertex-ordering for the given edge. –A flag indicating whether the vertex lie on the edge or extruded to infinity.

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware6 Generation of Shadow Volumes

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware7 Implementation  On ATI Radeon 9700 card using OpenGL.  Uses a floating point RGBA offscreen buffer.  Supports up to 12 light sources.  Propose –Texture access during vertex processing. –A fast, on the card copy from frame buffer to a vertex attribute array.

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware8 Result

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware9 Result

Alivn/GAME LAB/CSIE/NDHU Shadow Volumes on Programmable Graphics Hardware10 Conclusion & Future Work  Perform silhouette detection in hardware.  The shadowing objects can be transformed by vertex shader.  Buffer read-back are already visible in OpenGL 2.0 specification.  Solve the near/far plane intersection problem.  NPR