meaning of m34 of CATransform3D

perspective catransform3d
Xiangwei Wang picture Xiangwei Wang · Oct 7, 2010 · Viewed 10.8k times · Source

What's the meaning of m34 of the structure CATransform3D, I only know it can change the perspective, but what's the meaning when the value is -0.001 and 0.001?

Answer

Mihai Timar picture Mihai Timar · Sep 29, 2011

You can find the full details here. Note that Apple uses the reversed multiplication order for projection (relative to the given link) so all matrix multiplications are reversed and all matrices are transposed.

A short description of the meaning:

  • m34 = 1/z distance to projection plane (the 1/ez term in the reference link)
  • + for the z axis is towards the viewer, resulting in a "looking in the mirror" feel when using -
  • projection center is (0,0,0) plus any translations you set up

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