equalweightcombine_postmult.nvp

游戏编程精华02－含有几十个游戏编程例子

/*********************************************************************NVMH2****
Path:  C:\Dev\devrel\Nv_sdk_4\Dx8\NVEffectsBrowser\Effects\Dot3Bump_Dynamic
File:  EqualWeightCombine_PostMult.nvp

Copyright (C) 1999, 2000 NVIDIA Corporation
This file is provided without support, instruction, or implied warranty of any
kind.  NVIDIA makes no guarantee of its fitness for a particular purpose and is
not liable under any circumstances for any damages or loss whatsoever arising
from the use or inability to use this file or items derived from it.

Comments:

Simple pixel shader that samples all 4 texture stages, averages these
samples and outputs the result.  Offset each texture stage's iterated
coordinates by various amounts to sample a texels neighbors & blur.

*************************************************************************/


#include "PixelConstants.h"


; Declare pixel shader version
ps.1.1


def c7, 0.5, 0.5, 0.5, 1.0


; get colors from all 4 texture stages
tex t0		// 1st neighbor
tex t1		// 2nd neighbor
tex t2		// etc.
tex t3


; and average them according to weights in constant mem:
; r0 = fac * t0 + fac * t1 + fac * t2 + fac * t3
; We could to this:
// mul r0, c[PCN_MULTFACTOR], t0
// mad r1, c[PCN_MULTFACTOR], t1, r0
// mad r0, c[PCN_MULTFACTOR], t2, r1
// mad r0, c[PCN_MULTFACTOR], t3, r0
; But that would loose low bits of precision, so instead
;  we bias to 9 bit signed components and operate on those,
;  shifting the end result back to the [0,1] unsigned range


add_d2  r0, t0_bias, t1_bias
add_d2  r1, t2_bias, t3_bias

add_d2  r0, r0, r1

// bring back to the range [0,1]
add     r0, r0, c7