//------------------------------------------------------------------------------
// 4-tap filtering
//------------------------------------------------------------------------------
xps.1.1

// default filter is box filter, but this is easily overwritten using SetPixelShaderConstant

def c0, 0.25f, 0.25f, 0.25f, 0.25f
def c1, 0.25f, 0.25f, 0.25f, 0.25f 
def c2, 0.25f, 0.25f, 0.25f, 0.25f 
def c3, 0.25f, 0.25f, 0.25f, 0.25f 

// source textures
tex t0
tex t1
tex t2
tex t3

// simple way
// mul r0, c0, t0
// mad r0, c1, t1, r0
// mad r0, c2, t2, r0
// mad r0, c3, t3, r0

// This has better precision (assuming the xmma_x2 intermediates don't overflow):
xmma_x2 discard, discard, r0, c0, t0, c1, t1	// 2 * (c0 * t0 + c1 * t1)
xmma_x2 discard, discard, r1, c2, t2, c3, t3	// 2 * (c2 * t2 + c3 * t3)
add_d2 r0.rgb, r0, r1

// v0 contains a modulation factor
mul r0.rgb, r0, v0
+mov r0.a, 1-zero