src/mesa/swrast/s_fog.c

   1 /* $Id: s_fog.c,v 1.12 2001/05/03 22:13:32 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2001  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 "colormac.h"
  30 #include "context.h"
  31 #include "macros.h"
  32 #include "mmath.h"
  33
  34 #include "s_context.h"
  35 #include "s_fog.h"
  36 #include "s_pb.h"
  37
  38
  39 /*
  40  * Apply fog to an array of RGBA pixels.
  41  * Input:  n - number of pixels
  42  *         fog - array of interpolated screen-space fog coordinates in [0..1]
  43  *         red, green, blue, alpha - pixel colors
  44  * Output:  red, green, blue, alpha - fogged pixel colors
  45  */
  46 void
  47 _mesa_fog_rgba_pixels( const GLcontext *ctx,
  48                        GLuint n,
  49                        const GLfloat fog[],
  50                        GLchan rgba[][4] )
  51 {
  52    GLuint i;
  53    GLchan rFog, gFog, bFog;
  54
  55    UNCLAMPED_FLOAT_TO_CHAN(rFog, ctx->Fog.Color[RCOMP]);
  56    UNCLAMPED_FLOAT_TO_CHAN(gFog, ctx->Fog.Color[GCOMP]);
  57    UNCLAMPED_FLOAT_TO_CHAN(bFog, ctx->Fog.Color[BCOMP]);
  58
  59    for (i = 0; i < n; i++) {
  60       const GLfloat f = fog[i];
  61       const GLfloat g = 1.0 - f;
  62       rgba[i][RCOMP] = f * rgba[i][RCOMP] + g * rFog;
  63       rgba[i][GCOMP] = f * rgba[i][GCOMP] + g * gFog;
  64       rgba[i][BCOMP] = f * rgba[i][BCOMP] + g * bFog;
  65    }
  66 }
  67
  68
  69
  70 /*
  71  * Apply fog to an array of color index pixels.
  72  * Input:  n - number of pixels
  73  *         z - array of integer depth values
  74  *         index - pixel color indexes
  75  * Output:  index - fogged pixel color indexes
  76  */
  77 void
  78 _mesa_fog_ci_pixels( const GLcontext *ctx,
  79                      GLuint n, const GLfloat fog[], GLuint index[] )
  80 {
  81    GLuint idx = (GLuint) ctx->Fog.Index;
  82    GLuint i;
  83
  84    for (i = 0; i < n; i++) {
  85       const GLfloat f = CLAMP(fog[i], 0.0, 1.0);
  86       index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * idx);
  87    }
  88 }
  89
  90
  91
  92 /*
  93  * Calculate fog coords from window z values
  94  * Input:  n - number of pixels
  95  *         z - array of integer depth values
  96  *         red, green, blue, alpha - pixel colors
  97  * Output:  red, green, blue, alpha - fogged pixel colors
  98  *
  99  * Use lookup table & interpolation?
 100  */
 101 void
 102 _mesa_win_fog_coords_from_z( const GLcontext *ctx,
 103                              GLuint n,
 104                              const GLdepth z[],
 105                              GLfloat fogcoord[] )
 106 {
 107    const GLboolean ortho = (ctx->ProjectionMatrix.m[15] != 0.0F);
 108    const GLfloat p10 = ctx->ProjectionMatrix.m[10];
 109    const GLfloat p14 = ctx->ProjectionMatrix.m[14];
 110    const GLfloat tz = ctx->Viewport._WindowMap.m[MAT_TZ];
 111    GLfloat szInv;
 112    GLuint i;
 113
 114    if (ctx->Viewport._WindowMap.m[MAT_SZ] == 0.0)
 115       szInv = 1.0F;
 116    else
 117       szInv = 1.0F / ctx->Viewport._WindowMap.m[MAT_SZ];
 118
 119    /*
 120     * Note: to compute eyeZ from the ndcZ we have to solve the following:
 121     *
 122     *        p[10] * eyeZ + p[14] * eyeW
 123     * ndcZ = ---------------------------
 124     *        p[11] * eyeZ + p[15] * eyeW
 125     *
 126     * Thus:
 127     *
 128     *        p[14] * eyeW - p[15] * eyeW * ndcZ
 129     * eyeZ = ----------------------------------
 130     *             p[11] * ndcZ - p[10]
 131     *
 132     * If we note:
 133     *    a) if using an orthographic projection, p[11] = 0 and p[15] = 1.
 134     *    b) if using a perspective projection, p[11] = -1 and p[15] = 0.
 135     *    c) we assume eyeW = 1 (not always true- glVertex4)
 136     *
 137     * Then we can simplify the calculation of eyeZ quite a bit.  We do
 138     * separate calculations for the orthographic and perspective cases below.
 139     * Note that we drop a negative sign or two since they don't matter.
 140     */
 141
 142    switch (ctx->Fog.Mode) {
 143       case GL_LINEAR:
 144          {
 145             GLfloat fogEnd = ctx->Fog.End;
 146             GLfloat fogScale;
 147             if (ctx->Fog.Start == ctx->Fog.End)
 148                fogScale = 1.0;
 149             else
 150                fogScale = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 151             if (ortho) {
 152                for (i=0;i<n;i++) {
 153                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 154                   GLfloat eyez = (ndcz - p14) / p10;
 155                   if (eyez < 0.0)
 156                      eyez = -eyez;
 157                   fogcoord[i] = (fogEnd - eyez) * fogScale;
 158                }
 159             }
 160             else {
 161                /* perspective */
 162                for (i=0;i<n;i++) {
 163                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 164                   GLfloat eyez = p14 / (ndcz + p10);
 165                   if (eyez < 0.0)
 166                      eyez = -eyez;
 167                   fogcoord[i] = (fogEnd - eyez) * fogScale;
 168                }
 169             }
 170          }
 171          break;
 172       case GL_EXP:
 173          if (ortho) {
 174             for (i=0;i<n;i++) {
 175                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 176                GLfloat eyez = (ndcz - p14) / p10;
 177                if (eyez < 0.0)
 178                   eyez = -eyez;
 179                fogcoord[i] = exp( -ctx->Fog.Density * eyez );
 180             }
 181          }
 182          else {
 183             /* perspective */
 184             for (i=0;i<n;i++) {
 185                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 186                GLfloat eyez = p14 / (ndcz + p10);
 187                if (eyez < 0.0)
 188                   eyez = -eyez;
 189                fogcoord[i] = exp( -ctx->Fog.Density * eyez );
 190             }
 191          }
 192          break;
 193       case GL_EXP2:
 194          {
 195             GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 196             if (ortho) {
 197                for (i=0;i<n;i++) {
 198                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 199                   GLfloat eyez = (ndcz - p14) / p10;
 200                   GLfloat tmp = negDensitySquared * eyez * eyez;
 201 #if defined(__alpha__) || defined(__alpha)
 202                   /* XXX this underflow check may be needed for other systems*/
 203                   if (tmp < FLT_MIN_10_EXP)
 204                      tmp = FLT_MIN_10_EXP;
 205 #endif
 206                   fogcoord[i] = exp( tmp );
 207                }
 208             }
 209             else {
 210                /* perspective */
 211                for (i=0;i<n;i++) {
 212                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 213                   GLfloat eyez = p14 / (ndcz + p10);
 214                   GLfloat tmp = negDensitySquared * eyez * eyez;
 215 #if defined(__alpha__) || defined(__alpha)
 216                   /* XXX this underflow check may be needed for other systems*/
 217                   if (tmp < FLT_MIN_10_EXP)
 218                      tmp = FLT_MIN_10_EXP;
 219 #endif
 220                   fogcoord[i] = exp( tmp );
 221                }
 222             }
 223          }
 224          break;
 225       default:
 226          _mesa_problem(ctx, "Bad fog mode in _mesa_win_fog_coords_from_z");
 227          return;
 228    }
 229 }
 230
 231
 232 /*
 233  * Apply fog to an array of RGBA pixels.
 234  * Input:  n - number of pixels
 235  *         z - array of integer depth values
 236  *         red, green, blue, alpha - pixel colors
 237  * Output:  red, green, blue, alpha - fogged pixel colors
 238  */
 239 void
 240 _mesa_depth_fog_rgba_pixels( const GLcontext *ctx,
 241                              GLuint n, const GLdepth z[], GLchan rgba[][4] )
 242 {
 243    GLfloat fog[PB_SIZE];
 244    ASSERT(n <= PB_SIZE);
 245    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 246    _mesa_fog_rgba_pixels( ctx, n, fog, rgba );
 247 }
 248
 249
 250 /*
 251  * Apply fog to an array of color index pixels.
 252  * Input:  n - number of pixels
 253  *         z - array of integer depth values
 254  *         index - pixel color indexes
 255  * Output:  index - fogged pixel color indexes
 256  */
 257 void
 258 _mesa_depth_fog_ci_pixels( const GLcontext *ctx,
 259                      GLuint n, const GLdepth z[], GLuint index[] )
 260 {
 261    GLfloat fog[PB_SIZE];
 262    ASSERT(n <= PB_SIZE);
 263    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 264    _mesa_fog_ci_pixels( ctx, n, fog, index );
 265 }