To my knowledge UE4 supports the standard parallel projection and the ortho projection (at least in the editor). Other projections result in curving the edges of triangles. The GPU doesn’t have support for curved triangles so the only safe way to do this for wild projections is to render something like a cubemap and then apply the projection to the cubemap. As for VR, UE4 renders a larger parallel projection field of view, and then applies a warp to the output. This is part of the reason it is suggested to use some amount of screen percentage (150% is common) to super-sample a little to get a higher quality warp. The center is typically more under-sampled after the warp, while the edges are more over-sampled.