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This paper discusses the implementation and results of using shadow volumes on programmable graphics hardware. It covers motivation, silhouette detection, generation of shadow volumes, implementation details, and future work.
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Shadow Volumes on Programmable Graphics Hardware Speaker: Alvin Date: 2003/11/3 EUROGRAPHICS 2003
Outline • Motivation • Silhouette Detection • Generation of Shadow Volumes • Implementation • Result • Conclusion & Future Work Shadow Volumes on Programmable Graphics Hardware
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. Shadow Volumes on Programmable Graphics Hardware
Silhouette Detection Input Mesh Shadow Volumes on Programmable Graphics Hardware
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. Shadow Volumes on Programmable Graphics Hardware
Generation of Shadow Volumes Shadow Volumes on Programmable Graphics Hardware
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. Shadow Volumes on Programmable Graphics Hardware
Result Shadow Volumes on Programmable Graphics Hardware
Result Shadow Volumes on Programmable Graphics Hardware
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 Shadow Volumes on Programmable Graphics Hardware