Thanks again for your reply. I appreciate your responses but It seems I am not at all describing my intent clearly; I dont want to render a cube at runtime - I want to render the cubemap at compile/conditioning time. I will use the cubemap to render the texture onto my single face 3D mesh (not a cube) at runtime.
I probably am explaining this badly, so breaking it down might be more useful for other potential respondees.
1) I have a low poly, single face, 3D hull mesh, but no texture to draw on it. I already draw hundreds of these in my scene using hardware instancing. This is an interemediate step between my 2D billboards and my full textures, complex multi faced mesh.
2) I want to use a cubemap to decorate my 3D hull mesh using texCUBE.
3) This hull mesh represents a simplification of an existing but complex multi-faced mesh which I've converted into a hull for speed of rendering at medium distances.
4) I want my cube map texture to be generated at compile/conditioning time using the fully complex texture mesh, but I lack the knowledge of how to do this step.
In theory the image here http://philliphamlyn.files.wordpress.com/2013/07/image14.png illustrates what I expect my cube texture to look like BUT - this is generated through orthogonal projection, so its not useful as a cube map; to work for me each point on my hull must map to a coloured pixel on the cube map (using texCUBE) so my cube texture MUST be fully coloured, not an external projection.
Imagine my camera was at a point central to my 3D mesh. The magic of texCUBE is that it projects a ray from the centre onto the cube map, thereby preventing me from needing very complex texture coordinates. I want to reverse that process with my complex mesh so that the ray projected from within the centre of the mesh paints the object "from within". By doing this - essentailly a explosive projection of my mesh, I will generate a cube texture which can be used to drape any hull mesh of the same rought shape as the original mesh. To repeat; I will be doing this at compile/conditioning time - all I will do at render time is draw my hull mesh using the cube texture in a single batched hardware instanced call. This image might illustrate my thinking http://philliphamlyn.files.wordpress.com/2013/07/image17.png
I am beginning to think what I need is to use ray casting concepts here to get the intersect point from the mesh centre to the most distant mesh coloured surface and record that point manually on a cube texture, but that would mean casting one ray for each pixel on my destination cube texture; I had hoped there would be some kind of technique which would be better. Perhaps the only way to do this is to walk every possible cubemap pixel (not insurmountable) and cast a ray into the centre of me object and use the first surface pixel sampled - it will be correct from a projection point of view - its just so close to the normal process of perspective rendering that I think I must be missing something.
Edited by PhillipHamlyn, 22 July 2013 - 01:02 PM.