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/* $Id: alpha.c,v 1.4 1997/05/28 03:23:09 brianp Exp $ */
/*
* Mesa 3-D graphics library
* Version: 2.3
* Copyright (C) 1995-1997 Brian Paul
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the Free
* Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* $Log: alpha.c,v $
* Revision 1.4 1997/05/28 03:23:09 brianp
* added precompiled header (PCH) support
*
* Revision 1.3 1997/03/13 03:07:53 brianp
* optimized gl_alpha_test() by removing conditional from inside loops
*
* Revision 1.2 1996/09/15 14:15:54 brianp
* now use GLframebuffer and GLvisual
*
* Revision 1.1 1996/09/13 01:38:16 brianp
* Initial revision
*
*/
#ifdef PCH
#include "all.h"
#else
#include "alpha.h"
#include "context.h"
#include "types.h"
#include "dlist.h"
#include "macros.h"
#endif
void gl_AlphaFunc( GLcontext* ctx, GLenum func, GLclampf ref )
{
if (INSIDE_BEGIN_END(ctx)) {
gl_error( ctx, GL_INVALID_OPERATION, "glAlphaFunc" );
return;
}
switch (func) {
case GL_NEVER:
case GL_LESS:
case GL_EQUAL:
case GL_LEQUAL:
case GL_GREATER:
case GL_NOTEQUAL:
case GL_GEQUAL:
case GL_ALWAYS:
ctx->Color.AlphaFunc = func;
ctx->Color.AlphaRef = CLAMP( ref, 0.0F, 1.0F );
ctx->Color.AlphaRefUbyte = (GLubyte) (ctx->Color.AlphaRef
* ctx->Visual->AlphaScale);
break;
default:
gl_error( ctx, GL_INVALID_ENUM, "glAlphaFunc(func)" );
break;
}
}
/*
* Apply the alpha test to a span 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 gl_alpha_test( GLcontext* ctx,
GLuint n, const GLubyte alpha[], GLubyte mask[] )
{
GLuint i;
GLubyte ref = ctx->Color.AlphaRefUbyte;
/* switch cases ordered from most frequent to less frequent */
switch (ctx->Color.AlphaFunc) {
case GL_LESS:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] < ref);
}
return 1;
case GL_LEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] <= ref);
}
return 1;
case GL_GEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] >= ref);
}
return 1;
case GL_GREATER:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] > ref);
}
return 1;
case GL_NOTEQUAL:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] != ref);
}
return 1;
case GL_EQUAL:
for (i=0;i<n;i++) {
mask[i] &= (alpha[i] == 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;
}
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Netfuture.ch.