A 3D Wood shader.
Originally devised by Larry Gritz as a RMAN shader, now is here adapted to ISL. It has a bunch of parameters to play with. Orientation of the rings and grain can be changed in the code, changing the comented vectors and code lines. Is working in the X axis already.
It looks really nice in planar surfaces.
V1.5d: some code optimizations and adjusted min/max values of parameters.