src/mesa/drivers/dri/radeon/radeon_fog.c

   1 /**************************************************************************
   2
   3 Copyright 2000, 2001 ATI Technologies Inc., Ontario, Canada, and
   4                      VMware, Inc.
   5
   6 All Rights Reserved.
   7
   8 Permission is hereby granted, free of charge, to any person obtaining
   9 a copy of this software and associated documentation files (the
  10 "Software"), to deal in the Software without restriction, including
  11 without limitation the rights to use, copy, modify, merge, publish,
  12 distribute, sublicense, and/or sell copies of the Software, and to
  13 permit persons to whom the Software is furnished to do so, subject to
  14 the following conditions:
  15
  16 The above copyright notice and this permission notice (including the
  17 next paragraph) shall be included in all copies or substantial
  18 portions of the Software.
  19
  20 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  21 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  22 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  23 IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
  24 LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  25 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  26 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  27
  28 **************************************************************************/
  29
  30 /*
  31  * Authors:
  32  *   Keith Whitwell <keithw@vmware.com>
  33  */
  34
  35 #include "c99_math.h"
  36 #include "main/glheader.h"
  37 #include "main/imports.h"
  38 #include "main/context.h"
  39 #include "main/mtypes.h"
  40 #include "main/enums.h"
  41 #include "main/macros.h"
  42
  43 #include "radeon_screen.h"
  44 #include "radeon_fog.h"
  45
  46 /**********************************************************************/
  47 /*             Fog blend factor computation for hw tcl                */
  48 /*             same calculation used as in t_vb_fog.c                 */
  49 /**********************************************************************/
  50
  51 #define FOG_EXP_TABLE_SIZE 256
  52 #define FOG_MAX (10.0)
  53 #define EXP_FOG_MAX .0006595
  54 #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
  55 static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
  56
  57 #if 1
  58 #define NEG_EXP( result, narg )                                         \
  59 do {                                                                    \
  60    GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR));                       \
  61    GLint k = (GLint) f;                                                 \
  62    if (k > FOG_EXP_TABLE_SIZE-2)                                        \
  63       result = (GLfloat) EXP_FOG_MAX;                                   \
  64    else                                                                 \
  65       result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]);      \
  66 } while (0)
  67 #else
  68 #define NEG_EXP( result, narg )                                 \
  69 do {                                                            \
  70    result = exp(-narg);                                         \
  71 } while (0)
  72 #endif
  73
  74
  75 /**
  76  * Initialize the exp_table[] lookup table for approximating exp().
  77  */
  78 void
  79 radeonInitStaticFogData( void )
  80 {
  81    GLfloat f = 0.0F;
  82    GLint i = 0;
  83    for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
  84       exp_table[i] = (GLfloat) exp(-f);
  85    }
  86 }
  87
  88 /**
  89  * Compute per-vertex fog blend factors from fog coordinates by
  90  * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
  91  * Fog coordinates are distances from the eye (typically between the
  92  * near and far clip plane distances).
  93  * Note the fog (eye Z) coords may be negative so we use ABS(z) below.
  94  * Fog blend factors are in the range [0,1].
  95  */
  96 float
  97 radeonComputeFogBlendFactor( struct gl_context *ctx, GLfloat fogcoord )
  98 {
  99         GLfloat end  = ctx->Fog.End;
 100         GLfloat d, temp;
 101         const GLfloat z = fabsf(fogcoord);
 102
 103         switch (ctx->Fog.Mode) {
 104         case GL_LINEAR:
 105                 if (ctx->Fog.Start == ctx->Fog.End)
 106                         d = 1.0F;
 107                 else
 108                         d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
 109                 temp = (end - z) * d;
 110                 return CLAMP(temp, 0.0F, 1.0F);
 111                 break;
 112         case GL_EXP:
 113                 d = ctx->Fog.Density;
 114                 NEG_EXP( temp, d * z );
 115                 return temp;
 116                 break;
 117         case GL_EXP2:
 118                 d = ctx->Fog.Density*ctx->Fog.Density;
 119                 NEG_EXP( temp, d * z * z );
 120                 return temp;
 121                 break;
 122         default:
 123                 _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
 124                 return 0;
 125         }
 126 }
 127