I have a technique which I'm trying out, in order to reduce poly count on distant multi-textured objects. The approach is to generate a convex hull of the object and render that instead (when at a distance). I do this reasonably successfully for my shadows - although they are clearly not high quality shadows, for buildings and trees etc they suffice for me, and this means I can render only the hull on my shadow casting pass. However; I want to extend the low poly goodness of hull drawing by texturing my hull using a cube map.
In order to properly texture the 3D hull I want to use texCUBE to sample a cube map, prepared during conditioning, of the multi-textured mesh fully rendered.
Although I can create a "sky box" map of each of the faces of the original mesh (rotated orthogonally), its not what is needed here I dont think. I want to be able to reverse the process of texCUBE by projecting the mesh onto the texture render target "from within the mesh" - i.e. with the camera in the mesh centroid. I would hopefully generate a cube map of the mesh which I can later use with textCUBE to render my hull.
A couple of questions;
1) Is this approach common/reasonable ?
2) How do I go about projecting the cube map from my multi-textured mesh. The projection is neither Orthogonal or Perspective but "exploded", but I've no real idea whether that is feasible.