ZP+: Correct Z-pass stencil shadows

Samuel Hornus, Jared Hoberock, Sylvain Lefebvre, John Hart

Research output: Contribution to conferencePaper

Abstract

We present a novel algorithm for the rendering of hard shadows cast by a point light source. The well-known Z-pass method for rasterizing shadow volumes is not always correct. Our algorithm, which we call ZP+, elegantly corrects Z-pass defects. ZP+ takes advantage of triangle strips and the fast culling capabilities of graphics hardware not available to conventional robust methods like Z-fail. While Z-fail can be up to 80% slower than Z-pass, our new method ZP+ is typically less than 10% slower than Z-pass. Finally, we compare the three methods. When a scene is geometry-bound, ZP+ is always faster than Z-fail. We also explain why, in some situations, Z-pass (hence ZP+) is surprisingly slower than Z-fail on more recent graphics hardware.

Original languageEnglish (US)
Pages195-202
Number of pages8
StatePublished - Dec 30 2005
EventI3D 2005: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games - Washington, DC, United States
Duration: Apr 3 2005Apr 6 2005

Other

OtherI3D 2005: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games
CountryUnited States
CityWashington, DC
Period4/3/054/6/05

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Keywords

  • Graphics hardware
  • Real-time rendering
  • Shadow volume
  • Stencil shadows

ASJC Scopus subject areas

  • Software
  • Human-Computer Interaction
  • Computer Graphics and Computer-Aided Design

Cite this

Hornus, S., Hoberock, J., Lefebvre, S., & Hart, J. (2005). ZP+: Correct Z-pass stencil shadows. 195-202. Paper presented at I3D 2005: ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games, Washington, DC, United States.