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/* $Id: s_alpha.c,v 1.1 2000/10/31 18:00:04 keithw Exp $ */
/*
* Mesa 3-D graphics library
* Version: 3.3
*
* Copyright (C) 1999-2000 Brian Paul All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "glheader.h"
#include "context.h"
#include "colormac.h"
#include "macros.h"
#include "mmath.h"
#include "s_alpha.h"
/*
* Apply the alpha test to a span of pixels.
* In: rgba - array of pixels
* In/Out: mask - current pixel mask. Pixels which fail the alpha test
* will set the corresponding mask flag to 0.
* Return: 0 = all pixels in the span failed the alpha test.
* 1 = one or more pixels passed the alpha test.
*/
GLint
_mesa_alpha_test( const GLcontext *ctx,
GLuint n, CONST GLchan rgba[][4], GLubyte mask[] )
{
GLuint i;
GLchan ref = ctx->Color.AlphaRef;
/* switch cases ordered from most frequent to less frequent */
switch (ctx->Color.AlphaFunc) {
case GL_LESS:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] < ref);
}
return 1;
case GL_LEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] <= ref);
}
return 1;
case GL_GEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] >= ref);
}
return 1;
case GL_GREATER:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] > ref);
}
return 1;
case GL_NOTEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] != ref);
}
return 1;
case GL_EQUAL:
for (i=0;i<n;i++) {
mask[i] &= (rgba[i][ACOMP] == ref);
}
return 1;
case GL_ALWAYS:
/* do nothing */
return 1;
case GL_NEVER:
/* caller should check for zero! */
return 0;
default:
gl_problem( ctx, "Invalid alpha test in gl_alpha_test" );
return 0;
}
/* Never get here */
/*return 1;*/
}
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