Value meaning of M34 field in Catransform3d

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I can't explain it very clearly, said the wrong other children's shoes:

The structure of the transform is as follows:
struct CATRANSFORM3D
{
  CGFloat M11, M12, M13, M14;
  CGFloat M21, M22, M23, M24;
  CGFloat M31, M32, M33, M34;
  CGFloat M41, M42, M43, M44;
};

The first thing to do is to achieve a view (layer) perspective (which is nearly large and small) by setting M34:

Catransform3d rotationandperspectivetransform = catransform3didentity;
ROTATIONANDPERSPECTIVETRANSFORM.M34 = 1.0/-500;

M34 is responsible for the z-direction of the translation (move), m34= -1/d, the  default value is 0, that is, D infinity, which means that the layer in projection plane (projection surface) and layer in the world The coordinate coincide.

d The smaller the perspective effect, the more obvious.

The so-called D is the distance from the eye (Observer) to the projection plane.

Value meaning of M34 field in Catransform3d