Project cubemap to 2D texture

Question

I'd like to debug my render to cubemap function by projecting the whole thing to a 2D texture just like this one:

On my render from texture shader I've only got the UV texture coordinates available (ranging from (0,0) to (1,1)). How can I project the cubemap to the screen in a single draw call?

Answer 1

You can do this by rendering 6 quads and using 3D texture coords (s,t,p) pointing to each vertex of the cube so 8 variations of ( +/-1,+/-1,+/-1 ).

The UV 2D coords (s,t) like 4 variations of (0/1,0/1) are not usable for whole CUBE_MAP only for its individual sides.

Look for txr_skybox in here

• Normal mapping gone horribly wrong

on how CUBE_MAP is used in fragment shader.

PS in OpenGL the texture coords are called s,t,p,q instead of u,v,w,...

Here related QA:

• rendering cube map layout, understanding glTexCoord3f parameters