src/mesa/swrast/s_alpha.c

   1 /* $Id: s_alpha.c,v 1.5 2002/01/21 18:12:34 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->filledMask == GL_TRUE);
  53    ASSERT (span->filledAlpha == GL_TRUE);
  54
  55    SW_SPAN_SET_FLAG(span->testedAlpha);
  56
  57
  58    /* switch cases ordered from most frequent to less frequent */
  59    switch (ctx->Color.AlphaFunc) {
  60       case GL_LESS:
  61          for (i=span->start; i<span->end; i++) {
  62             mask[i] &= (rgba[i][ACOMP] < ref);
  63          }
  64          break;
  65       case GL_LEQUAL:
  66          for (i=span->start; i<span->end; i++)
  67             mask[i] &= (rgba[i][ACOMP] <= ref);
  68          break;
  69       case GL_GEQUAL:
  70          for (i=span->start; i<span->end; i++) {
  71             mask[i] &= (rgba[i][ACOMP] >= ref);
  72          }
  73          break;
  74       case GL_GREATER:
  75          for (i=span->start; i<span->end; i++) {
  76             mask[i] &= (rgba[i][ACOMP] > ref);
  77          }
  78          break;
  79       case GL_NOTEQUAL:
  80          for (i=span->start; i<span->end; i++) {
  81             mask[i] &= (rgba[i][ACOMP] != ref);
  82          }
  83          break;
  84       case GL_EQUAL:
  85          for (i=span->start; i<span->end; i++) {
  86             mask[i] &= (rgba[i][ACOMP] == ref);
  87          }
  88          break;
  89       case GL_ALWAYS:
  90          /* do nothing */
  91          return 1;
  92       case GL_NEVER:
  93          /* caller should check for zero! */
  94          return 0;
  95       default:
  96          _mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
  97          return 0;
  98    }
  99
 100    while ((span->start <= span->end)  &&
 101           (mask[span->start] == 0))
 102      span->start ++;
 103
 104    while ((span->end >= span->start)  &&
 105           (mask[span->end] == 0))
 106      span->end --;
 107
 108    span->writeAll = GL_FALSE;
 109
 110    if (span->start >= span->end)
 111      return 0;
 112    else
 113      return 1;
 114 }
 115
 116
 117 /*
 118  * Apply the alpha test to a span of pixels.
 119  * In:  rgba - array of pixels
 120  * In/Out:  mask - current pixel mask.  Pixels which fail the alpha test
 121  *                 will set the corresponding mask flag to 0.
 122  * Return:  0 = all pixels in the span failed the alpha test.
 123  *          1 = one or more pixels passed the alpha test.
 124  */
 125 GLint
 126 _old_alpha_test( const GLcontext *ctx,
 127                  GLuint n, CONST GLchan rgba[][4], GLubyte mask[] )
 128 {
 129    GLuint i;
 130    const GLchan ref = ctx->Color.AlphaRef;
 131
 132    /* switch cases ordered from most frequent to less frequent */
 133    switch (ctx->Color.AlphaFunc) {
 134       case GL_LESS:
 135          for (i=0;i<n;i++) {
 136             mask[i] &= (rgba[i][ACOMP] < ref);
 137          }
 138          return 1;
 139       case GL_LEQUAL:
 140          for (i=0;i<n;i++)
 141             mask[i] &= (rgba[i][ACOMP] <= ref);
 142          return 1;
 143       case GL_GEQUAL:
 144          for (i=0;i<n;i++) {
 145             mask[i] &= (rgba[i][ACOMP] >= ref);
 146          }
 147          return 1;
 148       case GL_GREATER:
 149          for (i=0;i<n;i++) {
 150             mask[i] &= (rgba[i][ACOMP] > ref);
 151          }
 152          return 1;
 153       case GL_NOTEQUAL:
 154          for (i=0;i<n;i++) {
 155             mask[i] &= (rgba[i][ACOMP] != ref);
 156          }
 157          return 1;
 158       case GL_EQUAL:
 159          for (i=0;i<n;i++) {
 160             mask[i] &= (rgba[i][ACOMP] == ref);
 161          }
 162          return 1;
 163       case GL_ALWAYS:
 164          /* do nothing */
 165          return 1;
 166       case GL_NEVER:
 167          /* caller should check for zero! */
 168          return 0;
 169       default:
 170          _mesa_problem( ctx, "Invalid alpha test in gl_alpha_test" );
 171          return 0;
 172    }
 173    /* Never get here */
 174    /*return 1;*/
 175 }