sharpenblit.nvp

来自「游戏编程精华02－含有几十个游戏编程例子」· NVP 代码 · 共 38 行

/************************************************************************
SharpenBlit.nvp

This pixel shader sharpens an input texture.  It explicitly encodes the 
following filter kernel in code:
      -1
       4
    -1  -1

The pixel shader assumes the same texture is sampled with appropriate 
offsets at all four texture units.  Texture t0 represents the center 
value; we thus compute
r0 = 4*t0 - t1 - t2 - t3

To avoid overflows the computation is reordered as:
r0 = t0 - t1 + t0 - t2 + t0 - t3 + t0

Copyright (C) 1999, 2000 NVIDIA Corporation
*************************************************************************/

; Declare pixel shader version
ps.1.1
	
; sample all 4 texture stages
tex t0          // this is the center sample
tex t1
tex t2
tex t3

; compute r0 = t0 - t1 + t0 - t2 + t0 - t3 + t0
mov     r0, t0
sub     r0, r0,   t1
add     r0, r0,   t0
sub     r0, r0,   t2
add     r0, r0,   t0
sub     r0, r0,   t3
add_sat r0, r0,   t0