I've been interested lately in environment mapped bump mapping. I can't seem to wrap my head around the technique however.
In Real-Time Rendering (Moeller & Haines) EMBM is described somewhat like this. A certain pixel is read from texture Coords u,v from a given bumpmap. This results in a new 2 dimensional vector that is transformed by a matrix and used to access a third environment map texture.
What I'm not understanding is how this is enough to generate any kind of effect. Because texture coordinates are provided on a per-vertex basis no real warboling (new word?) will occur within a given triangle. Rather, only at the verts themselves.
I'm obviously missing something here. Can someone please help?