neighborforcecalc.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:  NeighborForceCalc.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:

Step one in the nearest-neighbor force calculation for height-based water
simulation.  NeighborForceCalc2 is the second step.

This step takes the center point and three neighboring points, and computes
the texel difference as the "force" acting to pull the center texel.

The amount to which the computed force is applied to the texel is controlled
in a separate shader.

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




#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
;  t0 = center texel
;  t1 = 1st neighbor
;  t2 = 2nd neighbor - same axis as 1st neighbor point
;       so force for that axis == t1 - t0 + t2 - t0
;  t3 = 3rd neighbor on other axis

tex t0
tex t1
tex t2
tex t3


sub r0, t1, t0
sub r1, t2, t0

; 'force' for 1st axis
add r0, r0, r1        

; one more point for 2nd axis
sub r1, t3, t0
add r0, r0, r1


; Now add in a force to gently pull the center texel's 
;  value to 0.5.  The strength of this is controlled by
;  the PCN_EQ_REST_FAC  - restoration factor
; Without this, the simulation will fade to zero or fly
;  away to saturate at 1.0

sub r1, c7, t0
mad r0, r1, c[PCN_EQ_REST_FAC], r0


; shift up to center about 0.5
add r0, r0, c[PCN_ADDHALF]