# Chapter 25: Homogeneous Divide

## Outline

• Why it’s necessary to have the w at all for perspective (can’t we just divide by z?)
• i.e. the difference between w and z in clip space
• Mathematics behind it (projected coordinate systems)
• History behind left hand and right handed use in graphics (explanation of why OpenGL uses left-handed in clip space?)
• Possibility of using a projection matrix with inifinite far
• Precision issues in the depth buffer and ways to fix it
• Using the reversed “DirectX” mapping (0 to 1)
• Real logarithmic depth buffer using gl_FragDepth writes