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/* $Id: s_alpha.c,v 1.1 2003-02-28 11:49:40 pj Exp $ */
/*
* Mesa 3-D graphics library
* Version: 4.1
*
* Copyright (C) 1999-2002 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.
*/
/**
* \file swrast/s_alpha.c
* \brief Functions to apply alpha test.
*/
#include "glheader.h"
#include "context.h"
#include "colormac.h"
#include "macros.h"
#include "mmath.h"
#include "s_alpha.h"
#include "s_context.h"
/**
* \fn GLint _mesa_alpha_test( const GLcontext *ctx, struct sw_span *span )
* \brief Apply the alpha test to a span of pixels.
* \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, struct sw_span *span )
{
const GLchan (*rgba)[4] = (const GLchan (*)[4]) span->array->rgba;
GLchan ref;
const GLuint n = span->end;
GLubyte *mask = span->array->mask;
GLuint i;
CLAMPED_FLOAT_TO_CHAN(ref, ctx->Color.AlphaRef);
if (span->arrayMask & SPAN_RGBA) {
/* Use the array values */
switch (ctx->Color.AlphaFunc) {
case GL_LESS:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] < ref);
break;
case GL_LEQUAL:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] <= ref);
break;
case GL_GEQUAL:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] >= ref);
break;
case GL_GREATER:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] > ref);
break;
case GL_NOTEQUAL:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] != ref);
break;
case GL_EQUAL:
for (i = 0; i < n; i++)
mask[i] &= (rgba[i][ACOMP] == ref);
break;
case GL_ALWAYS:
/* do nothing */
return 1;
case GL_NEVER:
/* caller should check for zero! */
span->writeAll = GL_FALSE;
return 0;
default:
_mesa_problem( ctx, "Invalid alpha test in _mesa_alpha_test" );
return 0;
}
}
else {
/* Use the interpolation values */
#if CHAN_TYPE == GL_FLOAT
const GLfloat alphaStep = span->alphaStep;
GLfloat alpha = span->alpha;
ASSERT(span->interpMask & SPAN_RGBA);
switch (ctx->Color.AlphaFunc) {
case GL_LESS:
for (i = 0; i < n; i++) {
mask[i] &= (alpha < ref);
alpha += alphaStep;
}
break;
case GL_LEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (alpha <= ref);
alpha += alphaStep;
}
break;
case GL_GEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (alpha >= ref);
alpha += alphaStep;
}
break;
case GL_GREATER:
for (i = 0; i < n; i++) {
mask[i] &= (alpha > ref);
alpha += alphaStep;
}
break;
case GL_NOTEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (alpha != ref);
alpha += alphaStep;
}
break;
case GL_EQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (alpha == ref);
alpha += alphaStep;
}
break;
case GL_ALWAYS:
/* do nothing */
return 1;
case GL_NEVER:
/* caller should check for zero! */
span->writeAll = GL_FALSE;
return 0;
default:
_mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
return 0;
}
#else
/* 8 or 16-bit channel interpolation */
const GLfixed alphaStep = span->alphaStep;
GLfixed alpha = span->alpha;
ASSERT(span->interpMask & SPAN_RGBA);
switch (ctx->Color.AlphaFunc) {
case GL_LESS:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) < ref);
alpha += alphaStep;
}
break;
case GL_LEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) <= ref);
alpha += alphaStep;
}
break;
case GL_GEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) >= ref);
alpha += alphaStep;
}
break;
case GL_GREATER:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) > ref);
alpha += alphaStep;
}
break;
case GL_NOTEQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) != ref);
alpha += alphaStep;
}
break;
case GL_EQUAL:
for (i = 0; i < n; i++) {
mask[i] &= (FixedToChan(alpha) == ref);
alpha += alphaStep;
}
break;
case GL_ALWAYS:
/* do nothing */
return 1;
case GL_NEVER:
/* caller should check for zero! */
span->writeAll = GL_FALSE;
return 0;
default:
_mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
return 0;
}
#endif /* CHAN_TYPE */
}
#if 0
/* XXXX This causes conformance failures!!!! */
while ((span->start <= span->end) &&
(mask[span->start] == 0))
span->start ++;
while ((span->end >= span->start) &&
(mask[span->end] == 0))
span->end --;
#endif
span->writeAll = GL_FALSE;
if (span->start >= span->end)
return 0;
else
return 1;
}