I'm wondering if it is possible to generate a dynamic spherical environment map using a single frame render using a pincushion curvilinear perspective projection matrix (phew, that's a mouthful)?
I've been researching this for a few days now and the closest thing I can find is a curvilinear perspective but it isn't a commonly used projection matrix so there isn't any help I was easily able to find and I still don't know if it supports a full circle FOV.
The standard perspective matrix but it begins to look very strange and distorted above 180 degrees vertical FOV and completely fails to render when approaching 360 degrees. So instead most games render the scene six times using 90 degree FOV facing the faces of a cube.
Rendering the scene 6 times seems like a waste if it might be possible to simply imagine a camera that has a 360 degree view across both axis and then render that to a spherical environment map.