Screen Door TransparencyWith Alpha Textures

Alternative to polygon stipple



• Place screen door pattern in alpha texture
• Generate window-space texture coordinates
  • Enable GL_EYE_LINEAR texgen with texgen plane equations mimicking the projection & viewport transforms
  • Projective texturing’s division by “q” will mimic vertex coordinate’s division by “w”
• Use alpha testing to discard fragments based on screen door alpha texture
• Applies to both lines and polygons

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