reactos/dll/opengl/mesa/src/mesa/swrast/s_fog.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.2
   4  *
   5  * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 #include "main/glheader.h"
  27 #include "main/colormac.h"
  28 #include "main/macros.h"
  29
  30 #include "s_context.h"
  31 #include "s_fog.h"
  32
  33
  34 /**
  35  * Used to convert current raster distance to a fog factor in [0,1].
  36  */
  37 GLfloat
  38 _swrast_z_to_fogfactor(struct gl_context *ctx, GLfloat z)
  39 {
  40    GLfloat d, f;
  41
  42    switch (ctx->Fog.Mode) {
  43    case GL_LINEAR:
  44       if (ctx->Fog.Start == ctx->Fog.End)
  45          d = 1.0F;
  46       else
  47          d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
  48       f = (ctx->Fog.End - z) * d;
  49       return CLAMP(f, 0.0F, 1.0F);
  50    case GL_EXP:
  51       d = ctx->Fog.Density;
  52       f = EXPF(-d * z);
  53       f = CLAMP(f, 0.0F, 1.0F);
  54       return f;
  55    case GL_EXP2:
  56       d = ctx->Fog.Density;
  57       f = EXPF(-(d * d * z * z));
  58       f = CLAMP(f, 0.0F, 1.0F);
  59       return f;
  60    default:
  61       _mesa_problem(ctx, "Bad fog mode in _swrast_z_to_fogfactor");
  62       return 0.0;
  63    }
  64 }
  65
  66
  67 #define LINEAR_FOG(f, coord)  f = (fogEnd - coord) * fogScale
  68
  69 #define EXP_FOG(f, coord)  f = EXPF(density * coord)
  70
  71 #define EXP2_FOG(f, coord)                              \
  72 do {                                                    \
  73    GLfloat tmp = negDensitySquared * coord * coord;     \
  74    if (tmp < FLT_MIN_10_EXP)                            \
  75       tmp = FLT_MIN_10_EXP;                             \
  76    f = EXPF(tmp);                                       \
  77  } while(0)
  78
  79
  80 #define BLEND_FOG(f, coord)  f = coord
  81
  82
  83
  84 /**
  85  * Template code for computing fog blend factor and applying it to colors.
  86  * \param TYPE  either GLubyte, GLushort or GLfloat.
  87  * \param COMPUTE_F  code to compute the fog blend factor, f.
  88  */
  89 #define FOG_LOOP(TYPE, FOG_FUNC)                                                \
  90 if (span->arrayAttribs & FRAG_BIT_FOGC) {                                       \
  91    GLuint i;                                                                    \
  92    for (i = 0; i < span->end; i++) {                                            \
  93       const GLfloat fogCoord = span->array->attribs[FRAG_ATTRIB_FOGC][i][0];    \
  94       const GLfloat c = FABSF(fogCoord);                                        \
  95       GLfloat f, oneMinusF;                                                     \
  96       FOG_FUNC(f, c);                                                           \
  97       f = CLAMP(f, 0.0F, 1.0F);                                                 \
  98       oneMinusF = 1.0F - f;                                                     \
  99       rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog);          \
 100       rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog);          \
 101       rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog);          \
 102    }                                                                            \
 103 }                                                                               \
 104 else {                                                                          \
 105    const GLfloat fogStep = span->attrStepX[FRAG_ATTRIB_FOGC][0];                \
 106    GLfloat fogCoord = span->attrStart[FRAG_ATTRIB_FOGC][0];                     \
 107    const GLfloat wStep = span->attrStepX[FRAG_ATTRIB_WPOS][3];                  \
 108    GLfloat w = span->attrStart[FRAG_ATTRIB_WPOS][3];                            \
 109    GLuint i;                                                                    \
 110    for (i = 0; i < span->end; i++) {                                            \
 111       const GLfloat c = FABSF(fogCoord) / w;                                    \
 112       GLfloat f, oneMinusF;                                                     \
 113       FOG_FUNC(f, c);                                                           \
 114       f = CLAMP(f, 0.0F, 1.0F);                                                 \
 115       oneMinusF = 1.0F - f;                                                     \
 116       rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog);          \
 117       rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog);          \
 118       rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog);          \
 119       fogCoord += fogStep;                                                      \
 120       w += wStep;                                                               \
 121    }                                                                            \
 122 }
 123
 124 /**
 125  * Apply fog to a span of RGBA pixels.
 126  * The fog value are either in the span->array->fog array or interpolated from
 127  * the fog/fogStep values.
 128  * They fog values are either fog coordinates (Z) or fog blend factors.
 129  * _PreferPixelFog should be in sync with that state!
 130  */
 131 void
 132 _swrast_fog_rgba_span( const struct gl_context *ctx, SWspan *span )
 133 {
 134    const SWcontext *swrast = CONST_SWRAST_CONTEXT(ctx);
 135    GLfloat rFog, gFog, bFog;
 136
 137    ASSERT(swrast->_FogEnabled);
 138    ASSERT(span->arrayMask & SPAN_RGBA);
 139
 140    /* compute (scaled) fog color */
 141    if (span->array->ChanType == GL_UNSIGNED_BYTE) {
 142       rFog = ctx->Fog.Color[RCOMP] * 255.0F;
 143       gFog = ctx->Fog.Color[GCOMP] * 255.0F;
 144       bFog = ctx->Fog.Color[BCOMP] * 255.0F;
 145    }
 146    else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
 147       rFog = ctx->Fog.Color[RCOMP] * 65535.0F;
 148       gFog = ctx->Fog.Color[GCOMP] * 65535.0F;
 149       bFog = ctx->Fog.Color[BCOMP] * 65535.0F;
 150    }
 151    else {
 152       rFog = ctx->Fog.Color[RCOMP];
 153       gFog = ctx->Fog.Color[GCOMP];
 154       bFog = ctx->Fog.Color[BCOMP];
 155    }
 156
 157    if (swrast->_PreferPixelFog) {
 158       /* The span's fog values are fog coordinates, now compute blend factors
 159        * and blend the fragment colors with the fog color.
 160        */
 161       switch (ctx->Fog.Mode) {
 162       case GL_LINEAR:
 163          {
 164             const GLfloat fogEnd = ctx->Fog.End;
 165             const GLfloat fogScale = (ctx->Fog.Start == ctx->Fog.End)
 166                ? 1.0F : 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 167             if (span->array->ChanType == GL_UNSIGNED_BYTE) {
 168                GLubyte (*rgba)[4] = span->array->rgba8;
 169                FOG_LOOP(GLubyte, LINEAR_FOG);
 170             }
 171             else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
 172                GLushort (*rgba)[4] = span->array->rgba16;
 173                FOG_LOOP(GLushort, LINEAR_FOG);
 174             }
 175             else {
 176                GLfloat (*rgba)[4] = span->array->attribs[FRAG_ATTRIB_COL0];
 177                ASSERT(span->array->ChanType == GL_FLOAT);
 178                FOG_LOOP(GLfloat, LINEAR_FOG);
 179             }
 180          }
 181          break;
 182
 183       case GL_EXP:
 184          {
 185             const GLfloat density = -ctx->Fog.Density;
 186             if (span->array->ChanType == GL_UNSIGNED_BYTE) {
 187                GLubyte (*rgba)[4] = span->array->rgba8;
 188                FOG_LOOP(GLubyte, EXP_FOG);
 189             }
 190             else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
 191                GLushort (*rgba)[4] = span->array->rgba16;
 192                FOG_LOOP(GLushort, EXP_FOG);
 193             }
 194             else {
 195                GLfloat (*rgba)[4] = span->array->attribs[FRAG_ATTRIB_COL0];
 196                ASSERT(span->array->ChanType == GL_FLOAT);
 197                FOG_LOOP(GLfloat, EXP_FOG);
 198             }
 199          }
 200          break;
 201
 202       case GL_EXP2:
 203          {
 204             const GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 205             if (span->array->ChanType == GL_UNSIGNED_BYTE) {
 206                GLubyte (*rgba)[4] = span->array->rgba8;
 207                FOG_LOOP(GLubyte, EXP2_FOG);
 208             }
 209             else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
 210                GLushort (*rgba)[4] = span->array->rgba16;
 211                FOG_LOOP(GLushort, EXP2_FOG);
 212             }
 213             else {
 214                GLfloat (*rgba)[4] = span->array->attribs[FRAG_ATTRIB_COL0];
 215                ASSERT(span->array->ChanType == GL_FLOAT);
 216                FOG_LOOP(GLfloat, EXP2_FOG);
 217             }
 218          }
 219          break;
 220
 221       default:
 222          _mesa_problem(ctx, "Bad fog mode in _swrast_fog_rgba_span");
 223          return;
 224       }
 225    }
 226    else {
 227       /* The span's fog start/step/array values are blend factors in [0,1].
 228        * They were previously computed per-vertex.
 229        */
 230       if (span->array->ChanType == GL_UNSIGNED_BYTE) {
 231          GLubyte (*rgba)[4] = span->array->rgba8;
 232          FOG_LOOP(GLubyte, BLEND_FOG);
 233       }
 234       else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
 235          GLushort (*rgba)[4] = span->array->rgba16;
 236          FOG_LOOP(GLushort, BLEND_FOG);
 237       }
 238       else {
 239          GLfloat (*rgba)[4] = span->array->attribs[FRAG_ATTRIB_COL0];
 240          ASSERT(span->array->ChanType == GL_FLOAT);
 241          FOG_LOOP(GLfloat, BLEND_FOG);
 242       }
 243    }
 244 }