infer half vector length in BRDF
- by cician
it's my first question on stack.
Is it possible to infer length of the half angle vector for specular lighting from N·L and N·V without the whole view and light vectors?
I may be completely off-track, but I have this gut feeling it's possible...
Why? I'm working on a skin shader and I'm already doing one texture lookup with N·L+N·E and one texture lookup for specular with N·H+N·V. The latter one can be transformed into N·L+N·E lookup if only I had the half vector length.
Doing so could simplify the shader a bit and move some operations into the pre-computed lookup texture.
It would make a huge difference since I'm trying to squeeze as much functionality as possible to a single pass mobile version so instruction count matters.
Thanks.
