ps.1.1 

; grayscale formula
def c1, 0.30, 0.59, 0.11, 1.0 
                     
tex      t0                  
texcoord t1                 
dp3_sat r0, t1_bx2, t1_bx2
mul r0, c0, 1-r0            
mul r0, r0, t0              

; make grayscale
dp3 r0, r0, c1

