src/mesa/swrast/s_fog.c

   1 /* $Id: s_fog.c,v 1.3 2000/11/15 00:26:01 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2000  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
  37
  38 /*
  39  * Apply fog to an array of RGBA pixels.
  40  * Input:  n - number of pixels
  41  *         fog - array of interpolated screen-space fog coordinates in [0..1]
  42  *         red, green, blue, alpha - pixel colors
  43  * Output:  red, green, blue, alpha - fogged pixel colors
  44  */
  45 void
  46 _mesa_fog_rgba_pixels( const GLcontext *ctx,
  47                        GLuint n,
  48                        const GLfixed fog[],
  49                        GLchan rgba[][4] )
  50 {
  51    GLfixed rFog = ctx->Fog.Color[0] * CHAN_MAXF;
  52    GLfixed gFog = ctx->Fog.Color[1] * CHAN_MAXF;
  53    GLfixed bFog = ctx->Fog.Color[2] * CHAN_MAXF;
  54    GLuint i;
  55
  56    for (i=0;i<n;i++) {
  57       GLfixed f = CLAMP(fog[i], 0, FIXED_ONE);
  58       GLfixed g = FIXED_ONE - f;
  59       rgba[i][0] = (f*rgba[i][0] + g*rFog) >> FIXED_SHIFT;
  60       rgba[i][1] = (f*rgba[i][1] + g*gFog) >> FIXED_SHIFT;
  61       rgba[i][2] = (f*rgba[i][2] + g*bFog) >> FIXED_SHIFT;
  62    }
  63 }
  64
  65
  66
  67
  68 /*
  69  * Apply fog to an array of color index pixels.
  70  * Input:  n - number of pixels
  71  *         z - array of integer depth values
  72  *         index - pixel color indexes
  73  * Output:  index - fogged pixel color indexes
  74  */
  75 void
  76 _mesa_fog_ci_pixels( const GLcontext *ctx,
  77                      GLuint n, const GLfixed fog[], GLuint index[] )
  78 {
  79    GLuint idx = ctx->Fog.Index;
  80    GLuint i;
  81
  82    for (i=0;i<n;i++) {
  83       GLfixed f = FixedToFloat(CLAMP(fog[i], 0, FIXED_ONE));
  84       index[i] = (GLuint) ((GLfloat) index[i] + (1.0F-f) * idx);
  85    }
  86 }
  87
  88
  89
  90 /*
  91  * Calculate fog coords from window z values
  92  * Input:  n - number of pixels
  93  *         z - array of integer depth values
  94  *         red, green, blue, alpha - pixel colors
  95  * Output:  red, green, blue, alpha - fogged pixel colors
  96  *
  97  * Use lookup table & interpolation?
  98  */
  99 void
 100 _mesa_win_fog_coords_from_z( const GLcontext *ctx,
 101                              GLuint n,
 102                              const GLdepth z[],
 103                              GLfixed fogcoord[] )
 104 {
 105    const GLboolean ortho = (ctx->ProjectionMatrix.m[15] != 0.0F);
 106    const GLfloat p10 = ctx->ProjectionMatrix.m[10];
 107    const GLfloat p14 = ctx->ProjectionMatrix.m[14];
 108    const GLfloat tz = ctx->Viewport._WindowMap.m[MAT_TZ];
 109    const GLfloat szInv = 1.0F / ctx->Viewport._WindowMap.m[MAT_SZ];
 110    GLuint i;
 111
 112    /*
 113     * Note: to compute eyeZ from the ndcZ we have to solve the following:
 114     *
 115     *        p[10] * eyeZ + p[14] * eyeW
 116     * ndcZ = ---------------------------
 117     *        p[11] * eyeZ + p[15] * eyeW
 118     *
 119     * Thus:
 120     *
 121     *        p[14] * eyeW - p[15] * eyeW * ndcZ
 122     * eyeZ = ----------------------------------
 123     *             p[11] * ndcZ - p[10]
 124     *
 125     * If we note:
 126     *    a) if using an orthographic projection, p[11] = 0 and p[15] = 1.
 127     *    b) if using a perspective projection, p[11] = -1 and p[15] = 0.
 128     *    c) we assume eyeW = 1 (not always true- glVertex4)
 129     *
 130     * Then we can simplify the calculation of eyeZ quite a bit.  We do
 131     * separate calculations for the orthographic and perspective cases below.
 132     * Note that we drop a negative sign or two since they don't matter.
 133     */
 134
 135    switch (ctx->Fog.Mode) {
 136       case GL_LINEAR:
 137          {
 138             GLfloat fogEnd = ctx->Fog.End;
 139             GLfloat fogScale = (GLfloat) FIXED_ONE / (ctx->Fog.End -
 140                                                       ctx->Fog.Start);
 141             if (ortho) {
 142                for (i=0;i<n;i++) {
 143                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 144                   GLfloat eyez = (ndcz - p14) / p10;
 145                   if (eyez < 0.0)  eyez = -eyez;
 146                   fogcoord[i] = (GLint) ((fogEnd - eyez) * fogScale);
 147                }
 148             }
 149             else {
 150                /* perspective */
 151                for (i=0;i<n;i++) {
 152                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 153                   GLfloat eyez = p14 / (ndcz + p10);
 154                   if (eyez < 0.0)  eyez = -eyez;
 155                   fogcoord[i] = (GLint) ((fogEnd - eyez) * fogScale);
 156                }
 157             }
 158          }
 159          break;
 160       case GL_EXP:
 161          if (ortho) {
 162             for (i=0;i<n;i++) {
 163                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 164                GLfloat eyez = (ndcz - p14) / p10;
 165                if (eyez < 0.0) eyez = -eyez;
 166                fogcoord[i] = FloatToFixed(exp( -ctx->Fog.Density * eyez ));
 167             }
 168          }
 169          else {
 170             /* perspective */
 171             for (i=0;i<n;i++) {
 172                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 173                GLfloat eyez = p14 / (ndcz + p10);
 174                if (eyez < 0.0) eyez = -eyez;
 175                fogcoord[i] = FloatToFixed(exp( -ctx->Fog.Density * eyez ));
 176             }
 177          }
 178          break;
 179       case GL_EXP2:
 180          {
 181             GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 182             if (ortho) {
 183                for (i=0;i<n;i++) {
 184                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 185                   GLfloat eyez = (ndcz - p14) / p10;
 186                   GLfloat tmp = negDensitySquared * eyez * eyez;
 187 #if defined(__alpha__) || defined(__alpha)
 188                   /* XXX this underflow check may be needed for other systems*/
 189                   if (tmp < FLT_MIN_10_EXP)
 190                      tmp = FLT_MIN_10_EXP;
 191 #endif
 192                   fogcoord[i] = FloatToFixed(exp( tmp ));
 193                }
 194             }
 195             else {
 196                /* perspective */
 197                for (i=0;i<n;i++) {
 198                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 199                   GLfloat eyez = p14 / (ndcz + 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] = FloatToFixed(exp( tmp ));
 207                }
 208             }
 209          }
 210          break;
 211       default:
 212          gl_problem(ctx, "Bad fog mode in _mesa_win_fog_coords_from_z");
 213          return;
 214    }
 215 }
 216
 217
 218 /*
 219  * Apply fog to an array of RGBA pixels.
 220  * Input:  n - number of pixels
 221  *         z - array of integer depth values
 222  *         red, green, blue, alpha - pixel colors
 223  * Output:  red, green, blue, alpha - fogged pixel colors
 224  */
 225 void
 226 _mesa_depth_fog_rgba_pixels( const GLcontext *ctx,
 227                              GLuint n, const GLdepth z[], GLchan rgba[][4] )
 228 {
 229    GLfixed fog[MAX_WIDTH];
 230    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 231    _mesa_fog_rgba_pixels( ctx, n, fog, rgba );
 232 }
 233
 234
 235 /*
 236  * Apply fog to an array of color index pixels.
 237  * Input:  n - number of pixels
 238  *         z - array of integer depth values
 239  *         index - pixel color indexes
 240  * Output:  index - fogged pixel color indexes
 241  */
 242 void
 243 _mesa_depth_fog_ci_pixels( const GLcontext *ctx,
 244                      GLuint n, const GLdepth z[], GLuint index[] )
 245 {
 246    GLfixed fog[MAX_WIDTH];
 247    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 248    _mesa_fog_ci_pixels( ctx, n, fog, index );
 249 }
 250