| /************************************************************************** |
| |
| Copyright 2000, 2001 ATI Technologies Inc., Ontario, Canada, and |
| Tungsten Graphics Inc., Austin, Texas. |
| |
| All Rights Reserved. |
| |
| Permission is hereby granted, free of charge, to any person obtaining |
| a copy of this software and associated documentation files (the |
| "Software"), to deal in the Software without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Software, and to |
| permit persons to whom the Software is furnished to do so, subject to |
| the following conditions: |
| |
| The above copyright notice and this permission notice (including the |
| next paragraph) shall be included in all copies or substantial |
| portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
| IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE |
| LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION |
| OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION |
| WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
| |
| **************************************************************************/ |
| |
| /* |
| * Authors: |
| * Keith Whitwell <keith@tungstengraphics.com> |
| */ |
| |
| #include "main/glheader.h" |
| #include "main/imports.h" |
| #include "main/context.h" |
| #include "main/mtypes.h" |
| #include "main/enums.h" |
| #include "main/macros.h" |
| |
| #include "radeon_fog.h" |
| |
| /**********************************************************************/ |
| /* Fog blend factor computation for hw tcl */ |
| /* same calculation used as in t_vb_fog.c */ |
| /**********************************************************************/ |
| |
| #define FOG_EXP_TABLE_SIZE 256 |
| #define FOG_MAX (10.0) |
| #define EXP_FOG_MAX .0006595 |
| #define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE) |
| static GLfloat exp_table[FOG_EXP_TABLE_SIZE]; |
| |
| #if 1 |
| #define NEG_EXP( result, narg ) \ |
| do { \ |
| GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR)); \ |
| GLint k = (GLint) f; \ |
| if (k > FOG_EXP_TABLE_SIZE-2) \ |
| result = (GLfloat) EXP_FOG_MAX; \ |
| else \ |
| result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]); \ |
| } while (0) |
| #else |
| #define NEG_EXP( result, narg ) \ |
| do { \ |
| result = exp(-narg); \ |
| } while (0) |
| #endif |
| |
| |
| /** |
| * Initialize the exp_table[] lookup table for approximating exp(). |
| */ |
| void |
| radeonInitStaticFogData( void ) |
| { |
| GLfloat f = 0.0F; |
| GLint i = 0; |
| for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) { |
| exp_table[i] = (GLfloat) exp(-f); |
| } |
| } |
| |
| /** |
| * Compute per-vertex fog blend factors from fog coordinates by |
| * evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function. |
| * Fog coordinates are distances from the eye (typically between the |
| * near and far clip plane distances). |
| * Note the fog (eye Z) coords may be negative so we use ABS(z) below. |
| * Fog blend factors are in the range [0,1]. |
| */ |
| float |
| radeonComputeFogBlendFactor( struct gl_context *ctx, GLfloat fogcoord ) |
| { |
| GLfloat end = ctx->Fog.End; |
| GLfloat d, temp; |
| const GLfloat z = FABSF(fogcoord); |
| |
| switch (ctx->Fog.Mode) { |
| case GL_LINEAR: |
| if (ctx->Fog.Start == ctx->Fog.End) |
| d = 1.0F; |
| else |
| d = 1.0F / (ctx->Fog.End - ctx->Fog.Start); |
| temp = (end - z) * d; |
| return CLAMP(temp, 0.0F, 1.0F); |
| break; |
| case GL_EXP: |
| d = ctx->Fog.Density; |
| NEG_EXP( temp, d * z ); |
| return temp; |
| break; |
| case GL_EXP2: |
| d = ctx->Fog.Density*ctx->Fog.Density; |
| NEG_EXP( temp, d * z * z ); |
| return temp; |
| break; |
| default: |
| _mesa_problem(ctx, "Bad fog mode in make_fog_coord"); |
| return 0; |
| } |
| } |
| |