Conical Frustum

I’m new to OpenGL and need to modify some existing code. I’d like to change the existing perspective projection so that it looks like the viewer is looking through a cone, rather that a pyramid.

Can this be done by specifying the frustum to be non-rectangular? Or, do I have to clip things to a circle? If I have to clip myself, is this fairly easy to do?


Probably easiest to have a textured quad at the near clipping plane. The texture could have a black area with alpha = 1.0 and the middle would have alpha = 0.0 for the circle. Then use blending.