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 "glheader.h"
  30 #include "colormac.h"
  31 #include "context.h"
  32 #include "macros.h"
  33 #include "imports.h"
  34 #include "mtypes.h"
  35
  36 #include "math/m_xform.h"
  37
  38 #include "t_context.h"
  39 #include "t_pipeline.h"
  40
  41
  42 struct fog_stage_data {
  43    GLvector4f fogcoord;         /* has actual storage allocated */
  44    GLvector4f input;            /* points into VB->EyePtr Z values */
  45 };
  46
  47 #define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
  48
  49 #define FOG_EXP_TABLE_SIZE 256
  50 #define FOG_MAX (10.0)
  51 #define EXP_FOG_MAX .0006595
  52 #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
  53 static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
  54 static GLfloat inited = 0;
  55
  56 #if 1
  57 #define NEG_EXP( result, narg )                                         \
  58 do {                                                                    \
  59    GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));                       \
  60    GLint k = (GLint) f;                                                 \
  61    if (k > FOG_EXP_TABLE_SIZE-2)                                        \
  62       result = (GLfloat) EXP_FOG_MAX;                                   \
  63    else                                                                 \
  64       result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);      \
  65 } while (0)
  66 #else
  67 #define NEG_EXP( result, narg )                                 \
  68 do {                                                            \
  69    result = exp(-narg);                                         \
  70 } while (0)
  71 #endif
  72
  73
  74 /**
  75  * Initialize the exp_table[] lookup table for approximating exp().
  76  */
  77 static void
  78 init_static_data( void )
  79 {
  80    GLfloat f = 0.0F;
  81    GLint i = 0;
  82    for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
  83       exp_table[i] = EXPF(-f);
  84    }
  85    inited = 1;
  86 }
  87
  88
  89 /**
  90  * Compute per-vertex fog blend factors from fog coordinates by
  91  * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
  92  * Fog coordinates are distances from the eye (typically between the
  93  * near and far clip plane distances).
  94  * Note the fog (eye Z) coords may be negative so we use ABS(z) below.
  95  * Fog blend factors are in the range [0,1].
  96  */
  97 static void
  98 compute_fog_blend_factors(GLcontext *ctx, GLvector4f *out, const GLvector4f *in)
  99 {
 100    GLfloat end  = ctx->Fog.End;
 101    GLfloat *v = in->start;
 102    GLuint stride = in->stride;
 103    GLuint n = in->count;
 104    GLfloat (*data)[4] = out->data;
 105    GLfloat d;
 106    GLuint i;
 107
 108    out->count = in->count;
 109
 110    switch (ctx->Fog.Mode) {
 111    case GL_LINEAR:
 112       if (ctx->Fog.Start == ctx->Fog.End)
 113          d = 1.0F;
 114       else
 115          d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 116       for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
 117          const GLfloat z = *v;
 118          GLfloat f = (end - z) * d;
 119          data[i][0] = CLAMP(f, 0.0F, 1.0F);
 120       }
 121       break;
 122    case GL_EXP:
 123       d = ctx->Fog.Density;
 124       for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
 125          const GLfloat z = *v;
 126          NEG_EXP( data[i][0], d * z );
 127       }
 128       break;
 129    case GL_EXP2:
 130       d = ctx->Fog.Density*ctx->Fog.Density;
 131       for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
 132          const GLfloat z = *v;
 133          NEG_EXP( data[i][0], d * z * z );
 134       }
 135       break;
 136    default:
 137       _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
 138       return;
 139    }
 140 }
 141
 142
 143 static GLboolean
 144 run_fog_stage(GLcontext *ctx, struct tnl_pipeline_stage *stage)
 145 {
 146    TNLcontext *tnl = TNL_CONTEXT(ctx);
 147    struct vertex_buffer *VB = &tnl->vb;
 148    struct fog_stage_data *store = FOG_STAGE_DATA(stage);
 149    GLvector4f *input;
 150
 151    if (!ctx->Fog.Enabled || ctx->VertexProgram._Current)
 152       return GL_TRUE;
 153
 154
 155    if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {
 156       GLuint i;
 157       GLfloat *coord;
 158       /* Fog is computed from vertex or fragment Z values */
 159       /* source = VB->ObjPtr or VB->EyePtr coords */
 160       /* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
 161       VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;
 162
 163       if (!ctx->_NeedEyeCoords) {
 164          /* compute fog coords from object coords */
 165          const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
 166          GLfloat plane[4];
 167
 168          /* Use this to store calculated eye z values:
 169           */
 170          input = &store->fogcoord;
 171
 172          /* NOTE: negate plane here so we get positive fog coords! */
 173          /* NOTE2: this doesn't always work (tests/fog - all frag depth fog
 174             coords will be negative). */
 175          plane[0] = -m[2];
 176          plane[1] = -m[6];
 177          plane[2] = -m[10];
 178          plane[3] = -m[14];
 179          /* Full eye coords weren't required, just calculate the
 180           * eye Z values.
 181           */
 182          _mesa_dotprod_tab[VB->ObjPtr->size]( (GLfloat *) input->data,
 183                                               4 * sizeof(GLfloat),
 184                                               VB->ObjPtr, plane );
 185
 186          input->count = VB->ObjPtr->count;
 187
 188          /* make sure coords are really positive
 189             NOTE should avoid going through array twice */
 190          coord = input->start;
 191          for (i = 0; i < input->count; i++) {
 192             input->data[i][0] = FABSF(*coord);
 193             STRIDE_F(coord, input->stride);
 194          }
 195       }
 196       else {
 197          /* fog coordinates = eye Z coordinates (use ABS later) */
 198          input = &store->fogcoord;
 199
 200          if (VB->EyePtr->size < 2)
 201             _mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
 202
 203          input->stride = 4 * sizeof(GLfloat);
 204          input->count = VB->EyePtr->count;
 205          coord = VB->EyePtr->start;
 206          for (i = 0 ; i < VB->EyePtr->count; i++) {
 207             input->data[i][0] = FABSF(coord[2]);
 208             STRIDE_F(coord, VB->EyePtr->stride);
 209          }
 210       }
 211    }
 212    else {
 213       /* use glFogCoord() coordinates */
 214       input = VB->AttribPtr[_TNL_ATTRIB_FOG];  /* source data */
 215
 216       /* input->count may be one if glFogCoord was only called once
 217        * before glBegin.  But we need to compute fog for all vertices.
 218        */
 219       input->count = VB->ObjPtr->count;
 220
 221       VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;  /* dest data */
 222    }
 223
 224    if (tnl->_DoVertexFog) {
 225       /* compute blend factors from fog coordinates */
 226       compute_fog_blend_factors( ctx, VB->AttribPtr[_TNL_ATTRIB_FOG], input );
 227    }
 228    else {
 229       /* results = incoming fog coords (compute fog per-fragment later) */
 230       VB->AttribPtr[_TNL_ATTRIB_FOG] = input;
 231    }
 232
 233    VB->FogCoordPtr = VB->AttribPtr[_TNL_ATTRIB_FOG];
 234    return GL_TRUE;
 235 }
 236
 237
 238
 239 /* Called the first time stage->run() is invoked.
 240  */
 241 static GLboolean
 242 alloc_fog_data(GLcontext *ctx, struct tnl_pipeline_stage *stage)
 243 {
 244    TNLcontext *tnl = TNL_CONTEXT(ctx);
 245    struct fog_stage_data *store;
 246    stage->privatePtr = MALLOC(sizeof(*store));
 247    store = FOG_STAGE_DATA(stage);
 248    if (!store)
 249       return GL_FALSE;
 250
 251    _mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
 252    _mesa_vector4f_init( &store->input, 0, NULL );
 253
 254    if (!inited)
 255       init_static_data();
 256
 257    return GL_TRUE;
 258 }
 259
 260
 261 static void
 262 free_fog_data(struct tnl_pipeline_stage *stage)
 263 {
 264    struct fog_stage_data *store = FOG_STAGE_DATA(stage);
 265    if (store) {
 266       _mesa_vector4f_free( &store->fogcoord );
 267       FREE( store );
 268       stage->privatePtr = NULL;
 269    }
 270 }
 271
 272
 273 const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
 274 {
 275    "build fog coordinates",     /* name */
 276    NULL,                        /* private_data */
 277    alloc_fog_data,              /* dtr */
 278    free_fog_data,               /* dtr */
 279    NULL,                /* check */
 280    run_fog_stage                /* run -- initially set to init. */
 281 };