src/mesa/swrast/s_fog.c

   1 /* $Id: s_fog.c,v 1.9 2001/03/03 20:33:30 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 #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 GLfixed 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 #if CHAN_TYPE == GL_FLOAT
  60    for (i = 0; i < n; i++) {
  61       const GLfixed cf = CLAMP(fog[i], 0, FIXED_ONE);
  62       const GLfloat f = FixedToFloat(cf);
  63       const GLfloat g = 1.0F - f;
  64       rgba[i][RCOMP] = f * rgba[i][RCOMP] + g * rFog;
  65       rgba[i][GCOMP] = f * rgba[i][GCOMP] + g * gFog;
  66       rgba[i][BCOMP] = f * rgba[i][BCOMP] + g * bFog;
  67    }
  68 #else
  69    for (i = 0; i < n; i++) {
  70       const GLfixed f = CLAMP(fog[i], 0, FIXED_ONE);
  71       const GLfixed g = FIXED_ONE - f;
  72       rgba[i][0] = (f * rgba[i][0] + g * rFog) >> FIXED_SHIFT;
  73       rgba[i][1] = (f * rgba[i][1] + g * gFog) >> FIXED_SHIFT;
  74       rgba[i][2] = (f * rgba[i][2] + g * bFog) >> FIXED_SHIFT;
  75    }
  76 #endif
  77 }
  78
  79
  80
  81 /*
  82  * Apply fog to an array of color index pixels.
  83  * Input:  n - number of pixels
  84  *         z - array of integer depth values
  85  *         index - pixel color indexes
  86  * Output:  index - fogged pixel color indexes
  87  */
  88 void
  89 _mesa_fog_ci_pixels( const GLcontext *ctx,
  90                      GLuint n, const GLfixed fog[], GLuint index[] )
  91 {
  92    GLuint idx = ctx->Fog.Index;
  93    GLuint i;
  94
  95    for (i=0;i<n;i++) {
  96       GLfloat f = FixedToFloat(CLAMP(fog[i], 0, FIXED_ONE));
  97       index[i] = (GLuint) ((GLfloat) index[i] + (1.0F-f) * idx);
  98    }
  99 }
 100
 101
 102
 103 /*
 104  * Calculate fog coords from window z values
 105  * Input:  n - number of pixels
 106  *         z - array of integer depth values
 107  *         red, green, blue, alpha - pixel colors
 108  * Output:  red, green, blue, alpha - fogged pixel colors
 109  *
 110  * Use lookup table & interpolation?
 111  */
 112 void
 113 _mesa_win_fog_coords_from_z( const GLcontext *ctx,
 114                              GLuint n,
 115                              const GLdepth z[],
 116                              GLfixed fogcoord[] )
 117 {
 118    const GLboolean ortho = (ctx->ProjectionMatrix.m[15] != 0.0F);
 119    const GLfloat p10 = ctx->ProjectionMatrix.m[10];
 120    const GLfloat p14 = ctx->ProjectionMatrix.m[14];
 121    const GLfloat tz = ctx->Viewport._WindowMap.m[MAT_TZ];
 122    GLfloat szInv;
 123    GLuint i;
 124
 125    if (ctx->Viewport._WindowMap.m[MAT_SZ] == 0.0)
 126       szInv = 1.0F;
 127    else
 128       szInv = 1.0F / ctx->Viewport._WindowMap.m[MAT_SZ];
 129
 130    /*
 131     * Note: to compute eyeZ from the ndcZ we have to solve the following:
 132     *
 133     *        p[10] * eyeZ + p[14] * eyeW
 134     * ndcZ = ---------------------------
 135     *        p[11] * eyeZ + p[15] * eyeW
 136     *
 137     * Thus:
 138     *
 139     *        p[14] * eyeW - p[15] * eyeW * ndcZ
 140     * eyeZ = ----------------------------------
 141     *             p[11] * ndcZ - p[10]
 142     *
 143     * If we note:
 144     *    a) if using an orthographic projection, p[11] = 0 and p[15] = 1.
 145     *    b) if using a perspective projection, p[11] = -1 and p[15] = 0.
 146     *    c) we assume eyeW = 1 (not always true- glVertex4)
 147     *
 148     * Then we can simplify the calculation of eyeZ quite a bit.  We do
 149     * separate calculations for the orthographic and perspective cases below.
 150     * Note that we drop a negative sign or two since they don't matter.
 151     */
 152
 153    switch (ctx->Fog.Mode) {
 154       case GL_LINEAR:
 155          {
 156             GLfloat fogEnd = ctx->Fog.End;
 157             GLfloat fogScale;
 158             if (ctx->Fog.Start == ctx->Fog.End)
 159                fogScale = 1.0;
 160             else
 161                fogScale = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 162             if (ortho) {
 163                for (i=0;i<n;i++) {
 164                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 165                   GLfloat eyez = (ndcz - p14) / p10;
 166                   if (eyez < 0.0)
 167                      eyez = -eyez;
 168                   fogcoord[i] = FloatToFixed((fogEnd - eyez) * fogScale);
 169                }
 170             }
 171             else {
 172                /* perspective */
 173                for (i=0;i<n;i++) {
 174                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 175                   GLfloat eyez = p14 / (ndcz + p10);
 176                   if (eyez < 0.0)
 177                      eyez = -eyez;
 178                   fogcoord[i] = FloatToFixed((fogEnd - eyez) * fogScale);
 179                }
 180             }
 181          }
 182          break;
 183       case GL_EXP:
 184          if (ortho) {
 185             for (i=0;i<n;i++) {
 186                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 187                GLfloat eyez = (ndcz - p14) / p10;
 188                if (eyez < 0.0)
 189                   eyez = -eyez;
 190                fogcoord[i] = FloatToFixed(exp( -ctx->Fog.Density * eyez ));
 191             }
 192          }
 193          else {
 194             /* perspective */
 195             for (i=0;i<n;i++) {
 196                GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 197                GLfloat eyez = p14 / (ndcz + p10);
 198                if (eyez < 0.0)
 199                   eyez = -eyez;
 200                fogcoord[i] = FloatToFixed(exp( -ctx->Fog.Density * eyez ));
 201             }
 202          }
 203          break;
 204       case GL_EXP2:
 205          {
 206             GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
 207             if (ortho) {
 208                for (i=0;i<n;i++) {
 209                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 210                   GLfloat eyez = (ndcz - p14) / p10;
 211                   GLfloat tmp = negDensitySquared * eyez * eyez;
 212 #if defined(__alpha__) || defined(__alpha)
 213                   /* XXX this underflow check may be needed for other systems*/
 214                   if (tmp < FLT_MIN_10_EXP)
 215                      tmp = FLT_MIN_10_EXP;
 216 #endif
 217                   fogcoord[i] = FloatToFixed(exp( tmp ));
 218                }
 219             }
 220             else {
 221                /* perspective */
 222                for (i=0;i<n;i++) {
 223                   GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
 224                   GLfloat eyez = p14 / (ndcz + p10);
 225                   GLfloat tmp = negDensitySquared * eyez * eyez;
 226 #if defined(__alpha__) || defined(__alpha)
 227                   /* XXX this underflow check may be needed for other systems*/
 228                   if (tmp < FLT_MIN_10_EXP)
 229                      tmp = FLT_MIN_10_EXP;
 230 #endif
 231                   fogcoord[i] = FloatToFixed(exp( tmp ));
 232                }
 233             }
 234          }
 235          break;
 236       default:
 237          _mesa_problem(ctx, "Bad fog mode in _mesa_win_fog_coords_from_z");
 238          return;
 239    }
 240 }
 241
 242
 243 /*
 244  * Apply fog to an array of RGBA pixels.
 245  * Input:  n - number of pixels
 246  *         z - array of integer depth values
 247  *         red, green, blue, alpha - pixel colors
 248  * Output:  red, green, blue, alpha - fogged pixel colors
 249  */
 250 void
 251 _mesa_depth_fog_rgba_pixels( const GLcontext *ctx,
 252                              GLuint n, const GLdepth z[], GLchan rgba[][4] )
 253 {
 254    GLfixed fog[PB_SIZE];
 255    ASSERT(n <= PB_SIZE);
 256    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 257    _mesa_fog_rgba_pixels( ctx, n, fog, rgba );
 258 }
 259
 260
 261 /*
 262  * Apply fog to an array of color index pixels.
 263  * Input:  n - number of pixels
 264  *         z - array of integer depth values
 265  *         index - pixel color indexes
 266  * Output:  index - fogged pixel color indexes
 267  */
 268 void
 269 _mesa_depth_fog_ci_pixels( const GLcontext *ctx,
 270                      GLuint n, const GLdepth z[], GLuint index[] )
 271 {
 272    GLfixed fog[PB_SIZE];
 273    ASSERT(n <= PB_SIZE);
 274    _mesa_win_fog_coords_from_z( ctx, n, z, fog );
 275    _mesa_fog_ci_pixels( ctx, n, fog, index );
 276 }
 277