neighborforcecalc2_x2.nvp

游戏编程精华02－含有几十个游戏编程例子

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

2nd step of force calc for render-to-texture
water simulation.

Adds the 4th & final neighbor point to the 
force calc..

** This tweaked version multiplies the height
  difference by 2 so that waves are pulled
  toward that point. ** 

Bias and scale the values so 0 force is 0.5, 
  full negative force is 0.0, and full pos is
  1.0

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


#include "PixelConstants.h"


; Declare pixel shader version
ps.1.1


; t0 = center
; t1 = 2nd axis final point
; t2 = previous partial result texture


def c1, -0.5, -0.5, -0.5, 1.0


; get colors from all 4 texture stages
tex t0     // Center texel
tex t1     // 2nd axis neighbor point
tex t2     // previous partial force amount
		   // Result from t1 - t0 is added to this t2
		   //  partial result & output

; last element of neighbor force
;   result can be negative

sub_x2 r0, t1, t0


; We need to possibly subtract from previous result. 
; Our textures don't hold signed values, so we have to
;   use two force accumulations textures with additive
;   blending.
 

; If you want to further increase the magnitude of the
;   force in this direction, uncomment some of these lines
;add r0, r0, r0
;add r0, r0, t2
;add r0, r0, c1

add r0, r0, t2