127 lines
3.7 KiB
C
127 lines
3.7 KiB
C
/**************************************************************************
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Copyright 2000, 2001 ATI Technologies Inc., Ontario, Canada, and
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VMware, Inc.
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All Rights Reserved.
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice (including the
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next paragraph) shall be included in all copies or substantial
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portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
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LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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**************************************************************************/
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/*
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* Authors:
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* Keith Whitwell <keithw@vmware.com>
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*/
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#include "c99_math.h"
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#include "main/glheader.h"
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#include "main/context.h"
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#include "main/mtypes.h"
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#include "main/enums.h"
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#include "main/macros.h"
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#include "radeon_screen.h"
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#include "radeon_fog.h"
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/**********************************************************************/
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/* Fog blend factor computation for hw tcl */
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/* same calculation used as in t_vb_fog.c */
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/**********************************************************************/
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#define FOG_EXP_TABLE_SIZE 256
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#define FOG_MAX (10.0)
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#define EXP_FOG_MAX .0006595
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#define FOG_INCR (FOG_MAX/FOG_EXP_TABLE_SIZE)
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static GLfloat exp_table[FOG_EXP_TABLE_SIZE];
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#if 1
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#define NEG_EXP( result, narg ) \
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do { \
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GLfloat f = (GLfloat) (narg * (1.0/FOG_INCR)); \
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GLint k = (GLint) f; \
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if (k > FOG_EXP_TABLE_SIZE-2) \
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result = (GLfloat) EXP_FOG_MAX; \
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else \
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result = exp_table[k] + (f-k)*(exp_table[k+1]-exp_table[k]); \
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} while (0)
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#else
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#define NEG_EXP( result, narg ) \
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do { \
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result = exp(-narg); \
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} while (0)
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#endif
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/**
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* Initialize the exp_table[] lookup table for approximating exp().
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*/
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void
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radeonInitStaticFogData( void )
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{
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GLfloat f = 0.0F;
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GLint i = 0;
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for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
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exp_table[i] = (GLfloat) exp(-f);
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}
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}
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/**
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* Compute per-vertex fog blend factors from fog coordinates by
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* evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function.
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* Fog coordinates are distances from the eye (typically between the
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* near and far clip plane distances).
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* Note the fog (eye Z) coords may be negative so we use ABS(z) below.
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* Fog blend factors are in the range [0,1].
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*/
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float
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radeonComputeFogBlendFactor( struct gl_context *ctx, GLfloat fogcoord )
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{
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GLfloat end = ctx->Fog.End;
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GLfloat d, temp;
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const GLfloat z = fabsf(fogcoord);
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switch (ctx->Fog.Mode) {
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case GL_LINEAR:
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if (ctx->Fog.Start == ctx->Fog.End)
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d = 1.0F;
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else
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d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
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temp = (end - z) * d;
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return CLAMP(temp, 0.0F, 1.0F);
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break;
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case GL_EXP:
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d = ctx->Fog.Density;
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NEG_EXP( temp, d * z );
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return temp;
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break;
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case GL_EXP2:
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d = ctx->Fog.Density*ctx->Fog.Density;
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NEG_EXP( temp, d * z * z );
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return temp;
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break;
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default:
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_mesa_problem(ctx, "Bad fog mode in make_fog_coord");
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return 0;
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}
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}
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