// Declare pixel shader version
ps.1.1


// Define c[PCN_RED_MASK] as RGBA = (scale, 0, 0, 0)
//  Where scale [0,1] is applied to reduce the magnitude
//  of the s axis component of the normal.
// Define c[PCN_GREEN_MASK] similarly to affect the 
//  t axis component


// blue mask for r axis component (blue = up out of texture)

//@@def c4, 0.0, 0.0, 1.0, 1.0


def c2, 0.5, 0.5, 0.0, 0.0
def c1, 1.0, 1.0, 0.0, 0.0

def c3, 0.0, 0.0, 1.0, 0.0


// Get colors from all 4 texture stages
// These are the neighbor samples used to calculate slopes
//   for the surface displacements
// t0 = -s,  0
// t1 = +s,  0
// t2 =  0, +t
// t3 =  0, -t



tex t0
tex t1
tex t2
tex t3



// Source height from texture alpha!  This is to allow for packing
//  other data into the .rgb fields.


sub_x4  r0.a, t0, t1					// (t0 - t1)*4  : 4 for higher scale

mul     t0.rgb, r0.a, c[5]	// t0 = s result in red only
		
+ sub_x4  r1.a, t3, t2					// r1 = t result in alpha

mad     r0, r1.a, c[6], t0	// r0 = red,green for s and t result
//////
//@@@@@  the red and green masks may scale down the displacements.
//  they are subsequently scaled up below.  This looses precision, so
//  this should be re-coded to use mask values of 1.0 and scale 
//  the result after.


////////////////////////////////
// increase scale
// bases displacement about center 0.5 0.5

add_x2	r0, r0, r0

add     r0, r0, c2          // bias red,green to 0.5

add     r0, r0, c3			// add blue = 1.0