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143 lines
3.6 KiB
C
143 lines
3.6 KiB
C
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/* $Id: alpha.c,v 1.5 1997/07/24 01:24:28 brianp Exp $ */
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/*
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* Mesa 3-D graphics library
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* Version: 2.4
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* Copyright (C) 1995-1997 Brian Paul
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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* $Log: alpha.c,v $
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* Revision 1.5 1997/07/24 01:24:28 brianp
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* changed precompiled header symbol from PCH to PC_HEADER
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*
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* Revision 1.4 1997/05/28 03:23:09 brianp
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* added precompiled header (PCH) support
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*
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* Revision 1.3 1997/03/13 03:07:53 brianp
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* optimized gl_alpha_test() by removing conditional from inside loops
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*
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* Revision 1.2 1996/09/15 14:15:54 brianp
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* now use GLframebuffer and GLvisual
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*
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* Revision 1.1 1996/09/13 01:38:16 brianp
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* Initial revision
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*
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*/
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#ifdef PC_HEADER
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#include "all.h"
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#else
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#include "alpha.h"
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#include "context.h"
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#include "types.h"
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#include "dlist.h"
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#include "macros.h"
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#endif
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void gl_AlphaFunc( GLcontext* ctx, GLenum func, GLclampf ref )
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{
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if (INSIDE_BEGIN_END(ctx)) {
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gl_error( ctx, GL_INVALID_OPERATION, "glAlphaFunc" );
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return;
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}
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switch (func) {
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case GL_NEVER:
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case GL_LESS:
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case GL_EQUAL:
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case GL_LEQUAL:
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case GL_GREATER:
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case GL_NOTEQUAL:
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case GL_GEQUAL:
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case GL_ALWAYS:
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ctx->Color.AlphaFunc = func;
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ctx->Color.AlphaRef = CLAMP( ref, 0.0F, 1.0F );
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ctx->Color.AlphaRefUbyte = (GLubyte) (ctx->Color.AlphaRef
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* ctx->Visual->AlphaScale);
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break;
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default:
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gl_error( ctx, GL_INVALID_ENUM, "glAlphaFunc(func)" );
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break;
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}
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}
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/*
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* Apply the alpha test to a span of pixels.
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* In/Out: mask - current pixel mask. Pixels which fail the alpha test
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* will set the corresponding mask flag to 0.
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* Return: 0 = all pixels in the span failed the alpha test.
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* 1 = one or more pixels passed the alpha test.
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*/
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GLint gl_alpha_test( GLcontext* ctx,
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GLuint n, const GLubyte alpha[], GLubyte mask[] )
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{
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GLuint i;
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GLubyte ref = ctx->Color.AlphaRefUbyte;
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/* switch cases ordered from most frequent to less frequent */
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switch (ctx->Color.AlphaFunc) {
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case GL_LESS:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] < ref);
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}
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return 1;
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case GL_LEQUAL:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] <= ref);
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}
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return 1;
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case GL_GEQUAL:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] >= ref);
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}
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return 1;
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case GL_GREATER:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] > ref);
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}
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return 1;
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case GL_NOTEQUAL:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] != ref);
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}
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return 1;
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case GL_EQUAL:
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for (i=0;i<n;i++) {
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mask[i] &= (alpha[i] == ref);
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}
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return 1;
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case GL_ALWAYS:
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/* do nothing */
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return 1;
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case GL_NEVER:
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/* caller should check for zero! */
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return 0;
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default:
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gl_problem( ctx, "Invalid alpha test in gl_alpha_test" );
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return 0;
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}
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/* Never get here */
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return 1;
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}
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