ps.1.1

def c0, 0.0f, 0.0f, 0.0f, 0.5f
def c1, 0.0f, 0.0f, 0.0f, 0.9f

; sample all the texture stages
tex t0
tex t1
tex t2

; first interpolate the interpolator: using t0 straight produces ghosting 
; since the DoF selection is always hi-res (ie, t0) even for the blurred parts.
; playing with various combinations of t0, t1, t2 shows that the following
; is reasonable (depth-changing edges never get really unblurred)
; and yet only takes a single instruction.
lrp r0.a, c0, t2.a, t0.a

; although the following also produces good results (but with a bit of ghosting
; and two instructions)
; r0.a = 0.666*(.5*t2.a + .5*t1.a) + 0.333 * t0.a)
;      = 0.333*(t0.a+t1.a+t2.a)
; lrp r0.a, c0, t2.a, t1.a
; lrp r0.a, c1, r0.a, t0.a	

mov r0.rgb, r0.a