[Technically, this is not a BGE question, as this won’t be used in the BGE, but it could definitely be applied to it, and I figured you guys would know best what I meant by volumetric transparency.]
I’m looking for a GLSL shader script (fragment shader, if I am not mistaken) that will cheaply emulate volumetric transparency. That is, the amount of opacity depends on the distance between the near/facing face and the far/anti-facing face (either z-wise or normal-wise). This is similar to Blender 2.5’s volumetric material feature, but much cheaper.
I am sure this is possible in GLSL, but I wanted to see if something existed before I went to try to make it myself (if I do do this, I may want pointers). Something like alpha = 1 - 2^-thickness, probably, but computationally optimized (which I will do if I write it myself). It should be rather simple, though shading does become a little weird (don’t want the solid shading to happen anymore, but it can be dealt with, possibly by making it shadeless–that should look pretty decent, I think…).
I don’t need to worry about (I’ll pretend they’re rays) a ray hitting multiple facing faces before hitting an anti-facing face, because this is for a board-style game that involves a 3D grid of cubes.