Is it possible to make a projection matrix to not project in the center?

Question

I have the following projection matrix:

and I need to make a hole in the center of my matrix, something like that: (I don't want to project a custom W and H)

Is that possible ? Thanks.

Answer 1

It's not possible to cut a hole in the image by altering the projection matrix, no. However, you can mask out rendering in that region by using the depth test or stencil test.

For example, before rendering your scene, you could render a depth-only quad at the near plane to define the excluded region. Then any subsequent rendering will be clipped to outside of that region, because it will fail the depth test. The region doesn't have to be a rectangle with this approach, either; it can be any shape.