reactos/lib/mesa32/src/swrast/s_fog.c

   1
   2 /*
   3  * Mesa 3-D graphics library
   4  * Version:  4.1
   5  *
   6  * Copyright (C) 1999-2002  Brian Paul   All Rights Reserved.
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a
   9  * copy of this software and associated documentation files (the "Software"),
  10  * to deal in the Software without restriction, including without limitation
  11  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12  * and/or sell copies of the Software, and to permit persons to whom the
  13  * Software is furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included
  16  * in all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  21  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  22  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  23  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26
  27 #include "glheader.h"
  28 #include "colormac.h"
  29 #include "context.h"
  30 #include "macros.h"
  31
  32 #include "s_context.h"
  33 #include "s_fog.h"
  34 #include "s_span.h"
  35
  36
  37
  38
  39 /**
  40  * Used to convert current raster distance to a fog factor in [0,1].
  41  */
  42 GLfloat
  43 _swrast_z_to_fogfactor(GLcontext *ctx, GLfloat z)
  44 {
  45    GLfloat d, f;
  46
  47    switch (ctx->Fog.Mode) {
  48    case GL_LINEAR:
  49       if (ctx->Fog.Start == ctx->Fog.End)
  50          d = 1.0F;
  51       else
  52          d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
  53       f = (ctx->Fog.End - z) * d;
  54       return CLAMP(f, 0.0F, 1.0F);
  55    case GL_EXP:
  56       d = ctx->Fog.Density;
  57       f = (GLfloat) exp(-d * z);
  58       f = CLAMP(f, 0.0F, 1.0F);
  59       return f;
  60    case GL_EXP2:
  61       d = ctx->Fog.Density;
  62       f = (GLfloat) exp(-(d * d * z * z));
  63       f = CLAMP(f, 0.0F, 1.0F);
  64       return f;
  65    default:
  66       _mesa_problem(ctx, "Bad fog mode in _swrast_z_to_fogfactor");
  67       return 0.0;
  68    }
  69 }
  70
  71
  72 /**
  73  * Apply fog to a span of RGBA pixels.
  74  * The fog value are either in the span->array->fog array or interpolated from
  75  * the fog/fogStep values.
  76  * They fog values are either fog coordinates (Z) or fog blend factors.
  77  * _PreferPixelFog should be in sync with that state!
  78  */
  79 void
  80 _swrast_fog_rgba_span( const GLcontext *ctx, struct sw_span *span )
  81 {
  82    const SWcontext *swrast = SWRAST_CONTEXT(ctx);
  83    const GLchan rFog = swrast->_FogColor[RCOMP];
  84    const GLchan gFog = swrast->_FogColor[GCOMP];
  85    const GLchan bFog = swrast->_FogColor[BCOMP];
  86    const GLuint haveW = (span->interpMask & SPAN_W);
  87    GLchan (*rgba)[4] = (GLchan (*)[4]) span->array->rgba;
  88
  89    ASSERT(swrast->_FogEnabled);
  90    ASSERT((span->interpMask | span->arrayMask) & SPAN_FOG);
  91    ASSERT(span->arrayMask & SPAN_RGBA);
  92
  93    /* NOTE: if haveW is true, that means the fog start/step values are
  94     * perspective-corrected and we have to divide each fog coord by W.
  95     */
  96
  97    /* we need to compute fog blend factors */
  98    if (swrast->_PreferPixelFog) {
  99       /* The span's fog values are fog coordinates, now compute blend factors
 100        * and blend the fragment colors with the fog color.
 101        */
 102       switch (ctx->Fog.Mode) {
 103       case GL_LINEAR:
 104          {
 105             const GLfloat fogEnd = ctx->Fog.End;
 106             const GLfloat fogScale = (ctx->Fog.Start == ctx->Fog.End)
 107                ? 1.0F : 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 108             const GLfloat fogStep = span->fogStep;
 109             GLfloat fogCoord = span->fog;
 110             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 111             GLfloat w = haveW ? span->w : 1.0F;
 112             GLuint i;
 113             for (i = 0; i < span->end; i++) {
 114                GLfloat f, oneMinusF;
 115                f = (fogEnd - fogCoord / w) * fogScale;
 116                f = CLAMP(f, 0.0F, 1.0F);
 117                oneMinusF = 1.0F - f;
 118                rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
 119                rgba[i][GCOMP] = (GLchan) (f * rgba[i][GCOMP] + oneMinusF * gFog);
 120                rgba[i][BCOMP] = (GLchan) (f * rgba[i][BCOMP] + oneMinusF * bFog);
 121                fogCoord += fogStep;
 122                w += wStep;
 123             }
 124          }
 125          break;
 126       case GL_EXP:
 127          {
 128             const GLfloat density = -ctx->Fog.Density;
 129             const GLfloat fogStep = span->fogStep;
 130             GLfloat fogCoord = span->fog;
 131             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 132             GLfloat w = haveW ? span->w : 1.0F;
 133             GLuint i;
 134             for (i = 0; i < span->end; i++) {
 135                GLfloat f, oneMinusF;
 136                f = (GLfloat) exp(density * fogCoord / w);
 137                f = CLAMP(f, 0.0F, 1.0F);
 138                oneMinusF = 1.0F - f;
 139                rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
 140                rgba[i][GCOMP] = (GLchan) (f * rgba[i][GCOMP] + oneMinusF * gFog);
 141                rgba[i][BCOMP] = (GLchan) (f * rgba[i][BCOMP] + oneMinusF * bFog);
 142                fogCoord += fogStep;
 143                w += wStep;
 144             }
 145          }
 146          break;
 147       case GL_EXP2:
 148          {
 149             const GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 150             const GLfloat fogStep = span->fogStep;
 151             GLfloat fogCoord = span->fog;
 152             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 153             GLfloat w = haveW ? span->w : 1.0F;
 154             GLuint i;
 155             for (i = 0; i < span->end; i++) {
 156                const GLfloat coord = fogCoord / w;
 157                GLfloat tmp = negDensitySquared * coord * coord;
 158                GLfloat f, oneMinusF;
 159 #if defined(__alpha__) || defined(__alpha)
 160                /* XXX this underflow check may be needed for other systems*/
 161                if (tmp < FLT_MIN_10_EXP)
 162                   tmp = FLT_MIN_10_EXP;
 163 #endif
 164                f = (GLfloat) exp(tmp);
 165                f = CLAMP(f, 0.0F, 1.0F);
 166                oneMinusF = 1.0F - f;
 167                rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
 168                rgba[i][GCOMP] = (GLchan) (f * rgba[i][GCOMP] + oneMinusF * gFog);
 169                rgba[i][BCOMP] = (GLchan) (f * rgba[i][BCOMP] + oneMinusF * bFog);
 170                fogCoord += fogStep;
 171                w += wStep;
 172             }
 173          }
 174          break;
 175       default:
 176          _mesa_problem(ctx, "Bad fog mode in _swrast_fog_rgba_span");
 177          return;
 178       }
 179    }
 180    else if (span->arrayMask & SPAN_FOG) {
 181       /* The span's fog array values are blend factors.
 182        * They were previously computed per-vertex.
 183        */
 184       GLuint i;
 185       for (i = 0; i < span->end; i++) {
 186          const GLfloat f = span->array->fog[i];
 187          const GLfloat oneMinusF = 1.0F - f;
 188          rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
 189          rgba[i][GCOMP] = (GLchan) (f * rgba[i][GCOMP] + oneMinusF * gFog);
 190          rgba[i][BCOMP] = (GLchan) (f * rgba[i][BCOMP] + oneMinusF * bFog);
 191       }
 192    }
 193    else {
 194       /* The span's fog start/step values are blend factors.
 195        * They were previously computed per-vertex.
 196        */
 197       const GLfloat fogStep = span->fogStep;
 198       GLfloat fog = span->fog;
 199       const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 200       GLfloat w = haveW ? span->w : 1.0F;
 201       GLuint i;
 202       ASSERT(span->interpMask & SPAN_FOG);
 203       for (i = 0; i < span->end; i++) {
 204          const GLfloat fact = fog / w;
 205          const GLfloat oneMinusF = 1.0F - fact;
 206          rgba[i][RCOMP] = (GLchan) (fact * rgba[i][RCOMP] + oneMinusF * rFog);
 207          rgba[i][GCOMP] = (GLchan) (fact * rgba[i][GCOMP] + oneMinusF * gFog);
 208          rgba[i][BCOMP] = (GLchan) (fact * rgba[i][BCOMP] + oneMinusF * bFog);
 209          fog += fogStep;
 210          w += wStep;
 211       }
 212    }
 213 }
 214
 215
 216 /**
 217  * As above, but color index mode.
 218  */
 219 void
 220 _swrast_fog_ci_span( const GLcontext *ctx, struct sw_span *span )
 221 {
 222    const SWcontext *swrast = SWRAST_CONTEXT(ctx);
 223    const GLuint haveW = (span->interpMask & SPAN_W);
 224    const GLuint fogIndex = (GLuint) ctx->Fog.Index;
 225    GLuint *index = span->array->index;
 226
 227    ASSERT(swrast->_FogEnabled);
 228    ASSERT(span->arrayMask & SPAN_INDEX);
 229    ASSERT((span->interpMask | span->arrayMask) & SPAN_FOG);
 230
 231    /* we need to compute fog blend factors */
 232    if (swrast->_PreferPixelFog) {
 233       /* The span's fog values are fog coordinates, now compute blend factors
 234        * and blend the fragment colors with the fog color.
 235        */
 236       switch (ctx->Fog.Mode) {
 237       case GL_LINEAR:
 238          {
 239             const GLfloat fogEnd = ctx->Fog.End;
 240             const GLfloat fogScale = (ctx->Fog.Start == ctx->Fog.End)
 241                ? 1.0F : 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 242             const GLfloat fogStep = span->fogStep;
 243             GLfloat fogCoord = span->fog;
 244             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 245             GLfloat w = haveW ? span->w : 1.0F;
 246             GLuint i;
 247             for (i = 0; i < span->end; i++) {
 248                GLfloat f = (fogEnd - fogCoord / w) * fogScale;
 249                f = CLAMP(f, 0.0F, 1.0F);
 250                index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
 251                fogCoord += fogStep;
 252                w += wStep;
 253             }
 254          }
 255          break;
 256       case GL_EXP:
 257          {
 258             const GLfloat density = -ctx->Fog.Density;
 259             const GLfloat fogStep = span->fogStep;
 260             GLfloat fogCoord = span->fog;
 261             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 262             GLfloat w = haveW ? span->w : 1.0F;
 263             GLuint i;
 264             for (i = 0; i < span->end; i++) {
 265                GLfloat f = (GLfloat) exp(density * fogCoord / w);
 266                f = CLAMP(f, 0.0F, 1.0F);
 267                index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
 268                fogCoord += fogStep;
 269                w += wStep;
 270             }
 271          }
 272          break;
 273       case GL_EXP2:
 274          {
 275             const GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 276             const GLfloat fogStep = span->fogStep;
 277             GLfloat fogCoord = span->fog;
 278             const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 279             GLfloat w = haveW ? span->w : 1.0F;
 280             GLuint i;
 281             for (i = 0; i < span->end; i++) {
 282                const GLfloat coord = fogCoord / w;
 283                GLfloat tmp = negDensitySquared * coord * coord;
 284                GLfloat f;
 285 #if defined(__alpha__) || defined(__alpha)
 286                /* XXX this underflow check may be needed for other systems*/
 287                if (tmp < FLT_MIN_10_EXP)
 288                   tmp = FLT_MIN_10_EXP;
 289 #endif
 290                f = (GLfloat) exp(tmp);
 291                f = CLAMP(f, 0.0F, 1.0F);
 292                index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
 293                fogCoord += fogStep;
 294                w += wStep;
 295             }
 296          }
 297          break;
 298       default:
 299          _mesa_problem(ctx, "Bad fog mode in _swrast_fog_ci_span");
 300          return;
 301       }
 302    }
 303    else if (span->arrayMask & SPAN_FOG) {
 304       /* The span's fog array values are blend factors.
 305        * They were previously computed per-vertex.
 306        */
 307       GLuint i;
 308       for (i = 0; i < span->end; i++) {
 309          const GLfloat f = span->array->fog[i];
 310          index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
 311       }
 312    }
 313    else {
 314       /* The span's fog start/step values are blend factors.
 315        * They were previously computed per-vertex.
 316        */
 317       const GLfloat fogStep = span->fogStep;
 318       GLfloat fog = span->fog;
 319       const GLfloat wStep = haveW ? span->dwdx : 0.0F;
 320       GLfloat w = haveW ? span->w : 1.0F;
 321       GLuint i;
 322       ASSERT(span->interpMask & SPAN_FOG);
 323       for (i = 0; i < span->end; i++) {
 324          const GLfloat f = fog / w;
 325          index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
 326          fog += fogStep;
 327          w += wStep;
 328       }
 329    }
 330 }