// This shader creates a 2D color remap texture from 
// a blend of 2 color remap curves that are represented
// by a 1D texture.

// We can blend between two remapping curves using a blend amount
// specified in c0.a.

// We create a 2D texture so that it can be used in one pass on 
// the frame buffer with a texreg2ar and texreg2gb to remap the spaces.
// To accomplish this, we create texture coordinates that sample
// the texture both horizontally and vertically, then use
// constants to extract AG and RB channels and output them in
// the horizontal and vertical dimensions, respectively.
xps.1.1


def c0, 0,0,0,0 // this is the blend amount between each row
def c1, 0,1,0,1 // extracts the G and A portions 
def c2, 1,0,1,0 // extracts the R and B portions

// all stages are filled with the 1D color remap curve.
// t0 and t1 are mapped horizontally (first curve = t1, second curve = t2
// t2 and t3 are mapped vertically   (first curve = t2, second curve = t3
tex t0
tex t1
tex t2
tex t3

// r0 = blend of t0 and t1
lrp r0, c0.a, t1, t0
// r1 = blend of t2 and t3
lrp r1, c0.a, t3, t2
// extract the relavent portions of each and add them together
xmma discard, discard, r0, r0, c1, r1, c2