- The projection matrix is typically a scale and perspective projection.
- The projection transformation converts the viewing frustum into a cuboid shape.

- Projection matrices to perform depth-based calculations in depth buffer or fog effects.
- Computations such as these require that your projection matrix normalize w to be equivalent to world-space z.
- In short, if your projection matrix includes a (3,4) coefficient that is not 1.
- You must scale all the coefficients by the inverse of the (3,4) coefficient to make a proper matrix

Non Compliant Matrix

`a 0 0 0 0 b 0 0 0 0 c e 0 0 d 0`

Compliant Matrix

`a/e 0 0 0 0 b/e 0 0 0 0 c/e 1 0 0 d/e 0`