reactos/dll/opengl/mesa/src/mesa/tnl/t_vb_fog.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5
   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  * Authors:
  25  *    Keith Whitwell <keith@tungstengraphics.com>
  26  */
  27
  28
  29 #include "main/glheader.h"
  30 #include "main/colormac.h"
  31 #include "main/macros.h"
  32 #include "main/imports.h"
  33 #include "main/mtypes.h"
  34
  35 #include "math/m_xform.h"
  36
  37 #include "t_context.h"
  38 #include "t_pipeline.h"
  39
  40
  41 struct fog_stage_data {
  42    GLvector4f fogcoord;         /* has actual storage allocated */
  43 };
  44
  45 #define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
  46
  47 #define FOG_EXP_TABLE_SIZE 256
  48 #define FOG_MAX (10.0)
  49 #define EXP_FOG_MAX .0006595
  50 #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
  51 static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
  52 static GLfloat inited = 0;
  53
  54 #if 1
  55 #define NEG_EXP( result, narg )                                         \
  56 do {                                                                    \
  57    GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));                       \
  58    GLint k = (GLint) f;                                                 \
  59    if (k > FOG_EXP_TABLE_SIZE-2)                                        \
  60       result = (GLfloat) EXP_FOG_MAX;                                   \
  61    else                                                                 \
  62       result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);      \
  63 } while (0)
  64 #else
  65 #define NEG_EXP( result, narg )                                 \
  66 do {                                                            \
  67    result = exp(-narg);                                         \
  68 } while (0)
  69 #endif
  70
  71
  72 /**
  73  * Initialize the exp_table[] lookup table for approximating exp().
  74  */
  75 static void
  76 init_static_data( void )
  77 {
  78    GLfloat f = 0.0F;
  79    GLint i = 0;
  80    for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
  81       exp_table[i] = EXPF(-f);
  82    }
  83    inited = 1;
  84 }
  85
  86
  87 /**
  88  * Compute per-vertex fog blend factors from fog coordinates by
  89  * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
  90  * Fog coordinates are distances from the eye (typically between the
  91  * near and far clip plane distances).
  92  * Note that fogcoords may be negative, if eye z is source absolute
  93  * value must be taken earlier.
  94  * Fog blend factors are in the range [0,1].
  95  */
  96 static void
  97 compute_fog_blend_factors(struct gl_context *ctx, GLvector4f *out, const GLvector4f *in)
  98 {
  99    GLfloat end  = ctx->Fog.End;
 100    GLfloat *v = in->start;
 101    GLuint stride = in->stride;
 102    GLuint n = in->count;
 103    GLfloat (*data)[4] = out->data;
 104    GLfloat d;
 105    GLuint i;
 106
 107    out->count = in->count;
 108
 109    switch (ctx->Fog.Mode) {
 110    case GL_LINEAR:
 111       if (ctx->Fog.Start == ctx->Fog.End)
 112          d = 1.0F;
 113       else
 114          d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 115       for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
 116          const GLfloat z = *v;
 117          GLfloat f = (end - z) * d;
 118          data[i][0] = CLAMP(f, 0.0F, 1.0F);
 119       }
 120       break;
 121    case GL_EXP:
 122       d = ctx->Fog.Density;
 123       for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
 124          const GLfloat z = *v;
 125          NEG_EXP( data[i][0], d * z );
 126       }
 127       break;
 128    case GL_EXP2:
 129       d = ctx->Fog.Density*ctx->Fog.Density;
 130       for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
 131          const GLfloat z = *v;
 132          NEG_EXP( data[i][0], d * z * z );
 133       }
 134       break;
 135    default:
 136       _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
 137       return;
 138    }
 139 }
 140
 141
 142 static GLboolean
 143 run_fog_stage(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
 144 {
 145    TNLcontext *tnl = TNL_CONTEXT(ctx);
 146    struct vertex_buffer *VB = &tnl->vb;
 147    struct fog_stage_data *store = FOG_STAGE_DATA(stage);
 148    GLvector4f *input;
 149
 150
 151    if (!ctx->Fog.Enabled)
 152       return GL_TRUE;
 153
 154    if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {
 155       GLuint i;
 156       GLfloat *coord;
 157       /* Fog is computed from vertex or fragment Z values */
 158       /* source = VB->AttribPtr[_TNL_ATTRIB_POS] or VB->EyePtr coords */
 159       /* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
 160       VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;
 161
 162       if (!ctx->_NeedEyeCoords) {
 163          /* compute fog coords from object coords */
 164          const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
 165          GLfloat plane[4];
 166
 167          /* Use this to store calculated eye z values:
 168           */
 169          input = &store->fogcoord;
 170
 171          plane[0] = m[2];
 172          plane[1] = m[6];
 173          plane[2] = m[10];
 174          plane[3] = m[14];
 175          /* Full eye coords weren't required, just calculate the
 176           * eye Z values.
 177           */
 178          _mesa_dotprod_tab[VB->AttribPtr[_TNL_ATTRIB_POS]->size]
 179             ( (GLfloat *) input->data,
 180               4 * sizeof(GLfloat),
 181               VB->AttribPtr[_TNL_ATTRIB_POS], plane );
 182
 183          input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
 184
 185          /* make sure coords are really positive
 186             NOTE should avoid going through array twice */
 187          coord = input->start;
 188          for (i = 0; i < input->count; i++) {
 189             *coord = FABSF(*coord);
 190             STRIDE_F(coord, input->stride);
 191          }
 192       }
 193       else {
 194          /* fog coordinates = eye Z coordinates - need to copy for ABS */
 195          input = &store->fogcoord;
 196
 197          if (VB->EyePtr->size < 2)
 198             _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
 199
 200          input->stride = 4 * sizeof(GLfloat);
 201          input->count = VB->EyePtr->count;
 202          coord = VB->EyePtr->start;
 203          for (i = 0 ; i < VB->EyePtr->count; i++) {
 204             input->data[i][0] = FABSF(coord[2]);
 205             STRIDE_F(coord, VB->EyePtr->stride);
 206          }
 207       }
 208    }
 209    else {
 210       /* use glFogCoord() coordinates */
 211       input = VB->AttribPtr[_TNL_ATTRIB_FOG];  /* source data */
 212
 213       /* input->count may be one if glFogCoord was only called once
 214        * before glBegin.  But we need to compute fog for all vertices.
 215        */
 216       input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
 217
 218       VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;  /* dest data */
 219    }
 220
 221    if (tnl->_DoVertexFog) {
 222       /* compute blend factors from fog coordinates */
 223       compute_fog_blend_factors( ctx, VB->AttribPtr[_TNL_ATTRIB_FOG], input );
 224    }
 225    else {
 226       /* results = incoming fog coords (compute fog per-fragment later) */
 227       VB->AttribPtr[_TNL_ATTRIB_FOG] = input;
 228    }
 229
 230    return GL_TRUE;
 231 }
 232
 233
 234
 235 /* Called the first time stage->run() is invoked.
 236  */
 237 static GLboolean
 238 alloc_fog_data(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
 239 {
 240    TNLcontext *tnl = TNL_CONTEXT(ctx);
 241    struct fog_stage_data *store;
 242    stage->privatePtr = MALLOC(sizeof(*store));
 243    store = FOG_STAGE_DATA(stage);
 244    if (!store)
 245       return GL_FALSE;
 246
 247    _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
 248
 249    if (!inited)
 250       init_static_data();
 251
 252    return GL_TRUE;
 253 }
 254
 255
 256 static void
 257 free_fog_data(struct tnl_pipeline_stage *stage)
 258 {
 259    struct fog_stage_data *store = FOG_STAGE_DATA(stage);
 260    if (store) {
 261       _mesa_vector4f_free( &store->fogcoord );
 262       FREE( store );
 263       stage->privatePtr = NULL;
 264    }
 265 }
 266
 267
 268 const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
 269 {
 270    "build fog coordinates",     /* name */
 271    NULL,                        /* private_data */
 272    alloc_fog_data,              /* dtr */
 273    free_fog_data,               /* dtr */
 274    NULL,                /* check */
 275    run_fog_stage                /* run -- initially set to init. */
 276 };