src/mesa/swrast/s_alpha.c

   1 /* $Id: s_alpha.c,v 1.6 2002/01/27 18:32:03 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  4.1
   6  *
   7  * Copyright (C) 1999-2002  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 #include "glheader.h"
  29 #include "context.h"
  30 #include "colormac.h"
  31 #include "macros.h"
  32 #include "mmath.h"
  33
  34 #include "s_alpha.h"
  35
  36
  37 /*
  38  * Apply the alpha test to a span of pixels.
  39  * In:  rgba - array of pixels
  40  * In/Out:  span -
  41  * Return:  0 = all pixels in the span failed the alpha test.
  42  *          1 = one or more pixels passed the alpha test.
  43  */
  44 GLint
  45 _mesa_alpha_test( const GLcontext *ctx, struct sw_span *span,
  46                   CONST GLchan rgba[][4])
  47 {
  48    GLuint i;
  49    const GLchan ref = ctx->Color.AlphaRef;
  50    GLubyte *mask = span->mask;
  51
  52    ASSERT (span->filledAlpha == GL_TRUE || (span->arrayMask & SPAN_RGBA));
  53
  54    /* switch cases ordered from most frequent to less frequent */
  55    switch (ctx->Color.AlphaFunc) {
  56       case GL_LESS:
  57          for (i=span->start; i<span->end; i++) {
  58             mask[i] &= (rgba[i][ACOMP] < ref);
  59          }
  60          break;
  61       case GL_LEQUAL:
  62          for (i=span->start; i<span->end; i++)
  63             mask[i] &= (rgba[i][ACOMP] <= ref);
  64          break;
  65       case GL_GEQUAL:
  66          for (i=span->start; i<span->end; i++) {
  67             mask[i] &= (rgba[i][ACOMP] >= ref);
  68          }
  69          break;
  70       case GL_GREATER:
  71          for (i=span->start; i<span->end; i++) {
  72             mask[i] &= (rgba[i][ACOMP] > ref);
  73          }
  74          break;
  75       case GL_NOTEQUAL:
  76          for (i=span->start; i<span->end; i++) {
  77             mask[i] &= (rgba[i][ACOMP] != ref);
  78          }
  79          break;
  80       case GL_EQUAL:
  81          for (i=span->start; i<span->end; i++) {
  82             mask[i] &= (rgba[i][ACOMP] == ref);
  83          }
  84          break;
  85       case GL_ALWAYS:
  86          /* do nothing */
  87          return 1;
  88       case GL_NEVER:
  89          /* caller should check for zero! */
  90          return 0;
  91       default:
  92          _mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
  93          return 0;
  94    }
  95
  96 #if 0
  97    /* XXXX This causes conformance failures!!!! */
  98    while ((span->start <= span->end)  &&
  99           (mask[span->start] == 0))
 100      span->start ++;
 101
 102    while ((span->end >= span->start)  &&
 103           (mask[span->end] == 0))
 104      span->end --;
 105 #endif
 106    span->writeAll = GL_FALSE;
 107
 108    if (span->start >= span->end)
 109      return 0;
 110    else
 111      return 1;
 112 }
 113
 114
 115 /*
 116  * Apply the alpha test to a span of pixels.
 117  * In:  rgba - array of pixels
 118  * In/Out:  mask - current pixel mask.  Pixels which fail the alpha test
 119  *                 will set the corresponding mask flag to 0.
 120  * Return:  0 = all pixels in the span failed the alpha test.
 121  *          1 = one or more pixels passed the alpha test.
 122  */
 123 GLint
 124 _old_alpha_test( const GLcontext *ctx,
 125                  GLuint n, CONST GLchan rgba[][4], GLubyte mask[] )
 126 {
 127    GLuint i;
 128    const GLchan ref = ctx->Color.AlphaRef;
 129
 130    /* switch cases ordered from most frequent to less frequent */
 131    switch (ctx->Color.AlphaFunc) {
 132       case GL_LESS:
 133          for (i=0;i<n;i++) {
 134             mask[i] &= (rgba[i][ACOMP] < ref);
 135          }
 136          return 1;
 137       case GL_LEQUAL:
 138          for (i=0;i<n;i++)
 139             mask[i] &= (rgba[i][ACOMP] <= ref);
 140          return 1;
 141       case GL_GEQUAL:
 142          for (i=0;i<n;i++) {
 143             mask[i] &= (rgba[i][ACOMP] >= ref);
 144          }
 145          return 1;
 146       case GL_GREATER:
 147          for (i=0;i<n;i++) {
 148             mask[i] &= (rgba[i][ACOMP] > ref);
 149          }
 150          return 1;
 151       case GL_NOTEQUAL:
 152          for (i=0;i<n;i++) {
 153             mask[i] &= (rgba[i][ACOMP] != ref);
 154          }
 155          return 1;
 156       case GL_EQUAL:
 157          for (i=0;i<n;i++) {
 158             mask[i] &= (rgba[i][ACOMP] == ref);
 159          }
 160          return 1;
 161       case GL_ALWAYS:
 162          /* do nothing */
 163          return 1;
 164       case GL_NEVER:
 165          /* caller should check for zero! */
 166          return 0;
 167       default:
 168          _mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
 169          return 0;
 170    }
 171    /* Never get here */
 172    /*return 1;*/
 173 }