Depth Test (Z-test)

• Compare incoming fragment Z value with Z value in Z-buffer, accept or reject based on comparison

  • Same comparisons as with ALPHA test

• Biggest difference from Alpha test is that we must read the old Z value from the Z-buffer

  • ALPHA test uses same reference value for incoming pixels.
  • Note we can reject fragment early (don’t read Z-buffer) if test is GL_NEVER

• Same hardware requirements as Alpha test

  • Z value tends to be wider than alpha value, usually 16 bits.

Previous slide

Next slide

Back to first slide

View graphic version