ps_2_0
// create ray directions texture from camera parameters
// c0 - camera origin
// c1 - camera upleft direction
// c2 - camera direction step x
// c3 - camera direction step y
// t0 - coordinate
// oC0 - ray origin
// oC1 - ray direction
dcl t0
mov r0,t0.x
mov r2,c2
mad r1,r2,r0,c1
mov r0,t0.y
mov r3,c3
mad r1,r3,r0,r1
nrm r0,r1
mov oC0,r0
