Hello. I've implemented shadows for my point lights by rendering my scene to each of the 6 sides of a depth component cube map. It's working perfectly fine on OGL3 (DX10) level Nvidia and AMD cards, but after testing a bit I found out that there is a bug on Intel GPUs that causes the target parameter to be ignored when rendering to a cube map, meaning that it's only possible to render to the first face (POSITIVE_X) no matter which one I tell it to render to. I've reported this bug to Intel but there is no fix out yet (assuming there will be one). I also found out that depth component cube maps aren't supported on OGL2 hardware.
My first idea was to work around the problem by rendering the scene 6 times to a depth component 2D texture and copy the data from it to each face of the cube map. That should've worked around the Intel bug, but instead glCopyTexSubImage2D() gives me an Invalid Operation error even though it works on all other OGL3 level cards. I'm about to give up on this front.
On the OGL2 level cards, I can't use a depth cube map at all. I had this idea of copying the GL_DEPTH_COMPONENT16 texture to a GL_R16 cube map, but it gave me an invalid operation error. The only solution I can see is to create both a depth 2D render buffer and a color buffer to store depth in so I can later copy it to a color cube map.
- Is there any way to efficiently copy/convert a 16-bit depth component texture to a single channel 16-bit color cube map? Performance needs to be good since we're talking really old hardware, so PBOs and probably shaders are out of the question. The data is identical, it's just that the OGL spec seems to prohibit it.
- Is it really this hard to get point light shadows working well? Cube map shadows seem like a huge no-go to me even though it's the first thing that comes up when I Google. How did people do cube map shadows before OGL3?
- Would I be better off just implementing dual paraboloid shadow maps instead? That should solve all compatibility problems since I'd just need two normal 2D depth textures (or I could pack them into 1) instead of a cube map. It'd also be more CPU effective since it'd only be two render passes. How problematic is the seam and the distortion? How much worse is the quality compared to cube map shadows?