Tagging Pixels asShadowed or Unshadowed

Using stencil testing



• High-level algorithm does not say how to update only either pixels in or out of the shadow volume!
• The stenciling approach
  • Clear stencil buffer to zero and depth buffer to 1.0
  • Render scene to leave depth buffer with closest Zs
  • Render shadow volume into frame buffer with depth testing but without updating color and depth, but inverting a stencil bit
  • This leaves stencil bit set within shadow!

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