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/*
* Mesa 3-D graphics library
*
* Copyright (C) 1999-2006 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
* THE AUTHORS OR COPYRIGHT HOLDERS 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 "main/glheader.h"
#include "main/context.h"
#include "main/colormac.h"
#include "main/macros.h"
#include "s_alpha.h"
#include "s_context.h"
#define ALPHA_TEST(ALPHA, LOOP_CODE) \
do { \
switch (ctx->Color.AlphaFunc) { \
case GL_LESS: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA < ref); \
LOOP_CODE; \
} \
break; \
case GL_LEQUAL: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA <= ref); \
LOOP_CODE; \
} \
break; \
case GL_GEQUAL: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA >= ref); \
LOOP_CODE; \
} \
break; \
case GL_GREATER: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA > ref); \
LOOP_CODE; \
} \
break; \
case GL_NOTEQUAL: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA != ref); \
LOOP_CODE; \
} \
break; \
case GL_EQUAL: \
for (i = 0; i < n; i++) { \
mask[i] &= (ALPHA == ref); \
LOOP_CODE; \
} \
break; \
default: \
_mesa_problem(ctx, "Invalid alpha test in _swrast_alpha_test" ); \
return 0; \
} \
} while (0)
/**
* Perform the alpha test for an array of pixels.
* For pixels that fail the test, mask[i] will be set to 0.
* \return 0 if all pixels in the span failed the alpha test,
* 1 if one or more pixels passed the alpha test.
*/
GLint
_swrast_alpha_test(const struct gl_context *ctx, SWspan *span)
{
const GLuint n = span->end;
GLubyte *mask = span->array->mask;
GLuint i;
if (ctx->Color.AlphaFunc == GL_ALWAYS) {
/* do nothing */
return 1;
}
else if (ctx->Color.AlphaFunc == GL_NEVER) {
/* All pixels failed - caller should check for this return value and
* act accordingly.
*/
span->writeAll = GL_FALSE;
return 0;
}
if (span->arrayMask & SPAN_RGBA) {
/* Use array's alpha values */
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
GLubyte (*rgba)[4] = span->array->rgba8;
GLubyte ref;
CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
ALPHA_TEST(rgba[i][ACOMP], ;);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
GLushort (*rgba)[4] = span->array->rgba16;
GLushort ref;
CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
ALPHA_TEST(rgba[i][ACOMP], ;);
}
else {
GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
const GLfloat ref = ctx->Color.AlphaRef;
ALPHA_TEST(rgba[i][ACOMP], ;);
}
}
else {
/* Interpolate alpha values */
ASSERT(span->interpMask & SPAN_RGBA);
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
const GLfixed alphaStep = span->alphaStep;
GLfixed alpha = span->alpha;
GLubyte ref;
CLAMPED_FLOAT_TO_UBYTE(ref, ctx->Color.AlphaRef);
ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
const GLfixed alphaStep = span->alphaStep;
GLfixed alpha = span->alpha;
GLushort ref;
CLAMPED_FLOAT_TO_USHORT(ref, ctx->Color.AlphaRef);
ALPHA_TEST(FixedToInt(alpha), alpha += alphaStep);
}
else {
const GLfloat alphaStep = FixedToFloat(span->alphaStep);
GLfloat alpha = FixedToFloat(span->alpha);
const GLfloat ref = ctx->Color.AlphaRef;
ALPHA_TEST(alpha, alpha += alphaStep);
}
}
span->writeAll = GL_FALSE;
/* XXX examine mask[] values? */
return 1;
}
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