20160315 - Grading Via GCN Cube Instruction

Have a new idea for color grading which didn't make the cut for the GDC talk, involves grading the RGB ratio, color.rgb/max3(color.r,color.g,color.b), instead of color.rgb. Fits in with the tonemapper presented in the talk. Idea being to have consistent color changes regardless of intensity. Might be possible to use GCN's cubemap face instruction to reduce to a 3 layer 2D texture (for either increased quality in comparison with a 3D lookup, or reduced memory traffic). Also wanted to work out a process in which a user could choose among a set of image swatches to ballpark the display transform function (Rec.709, sRGB, fixed Gamma), but not fully satisfied with the results yet.