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265 lines
7.4 KiB
C
265 lines
7.4 KiB
C
/*
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* Mesa 3-D graphics library
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* Version: 6.5
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*
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* Copyright (C) 1999-2006 Brian Paul All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* Authors:
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* Keith Whitwell <keith@tungstengraphics.com>
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*/
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#include <precomp.h>
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struct fog_stage_data {
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GLvector4f fogcoord; /* has actual storage allocated */
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};
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#define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
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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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static GLfloat inited = 0;
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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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static void
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init_static_data( 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] = EXPF(-f);
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}
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inited = 1;
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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 that fogcoords may be negative, if eye z is source absolute
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* value must be taken earlier.
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* Fog blend factors are in the range [0,1].
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*/
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static void
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compute_fog_blend_factors(struct gl_context *ctx, GLvector4f *out, const GLvector4f *in)
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{
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GLfloat end = ctx->Fog.End;
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GLfloat *v = in->start;
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GLuint stride = in->stride;
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GLuint n = in->count;
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GLfloat (*data)[4] = out->data;
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GLfloat d;
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GLuint i;
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out->count = in->count;
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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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for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
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const GLfloat z = *v;
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GLfloat f = (end - z) * d;
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data[i][0] = CLAMP(f, 0.0F, 1.0F);
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}
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break;
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case GL_EXP:
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d = ctx->Fog.Density;
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for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
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const GLfloat z = *v;
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NEG_EXP( data[i][0], d * z );
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}
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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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for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
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const GLfloat z = *v;
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NEG_EXP( data[i][0], d * z * z );
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}
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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;
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}
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}
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static GLboolean
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run_fog_stage(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
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{
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TNLcontext *tnl = TNL_CONTEXT(ctx);
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struct vertex_buffer *VB = &tnl->vb;
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struct fog_stage_data *store = FOG_STAGE_DATA(stage);
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GLvector4f *input;
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if (!ctx->Fog.Enabled)
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return GL_TRUE;
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if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT) {
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GLuint i;
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GLfloat *coord;
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/* Fog is computed from vertex or fragment Z values */
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/* source = VB->AttribPtr[_TNL_ATTRIB_POS] or VB->EyePtr coords */
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/* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
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VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;
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if (!ctx->_NeedEyeCoords) {
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/* compute fog coords from object coords */
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const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
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GLfloat plane[4];
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/* Use this to store calculated eye z values:
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*/
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input = &store->fogcoord;
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plane[0] = m[2];
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plane[1] = m[6];
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plane[2] = m[10];
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plane[3] = m[14];
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/* Full eye coords weren't required, just calculate the
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* eye Z values.
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*/
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_mesa_dotprod_tab[VB->AttribPtr[_TNL_ATTRIB_POS]->size]
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( (GLfloat *) input->data,
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4 * sizeof(GLfloat),
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VB->AttribPtr[_TNL_ATTRIB_POS], plane );
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input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
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/* make sure coords are really positive
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NOTE should avoid going through array twice */
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coord = input->start;
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for (i = 0; i < input->count; i++) {
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*coord = FABSF(*coord);
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STRIDE_F(coord, input->stride);
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}
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}
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else {
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/* fog coordinates = eye Z coordinates - need to copy for ABS */
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input = &store->fogcoord;
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if (VB->EyePtr->size < 2)
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_mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
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input->stride = 4 * sizeof(GLfloat);
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input->count = VB->EyePtr->count;
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coord = VB->EyePtr->start;
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for (i = 0 ; i < VB->EyePtr->count; i++) {
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input->data[i][0] = FABSF(coord[2]);
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STRIDE_F(coord, VB->EyePtr->stride);
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}
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}
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}
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else {
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/* use glFogCoord() coordinates */
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input = VB->AttribPtr[_TNL_ATTRIB_FOG]; /* source data */
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/* input->count may be one if glFogCoord was only called once
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* before glBegin. But we need to compute fog for all vertices.
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*/
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input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
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VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord; /* dest data */
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}
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if (tnl->_DoVertexFog) {
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/* compute blend factors from fog coordinates */
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compute_fog_blend_factors( ctx, VB->AttribPtr[_TNL_ATTRIB_FOG], input );
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}
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else {
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/* results = incoming fog coords (compute fog per-fragment later) */
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VB->AttribPtr[_TNL_ATTRIB_FOG] = input;
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}
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return GL_TRUE;
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}
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/* Called the first time stage->run() is invoked.
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*/
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static GLboolean
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alloc_fog_data(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
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{
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TNLcontext *tnl = TNL_CONTEXT(ctx);
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struct fog_stage_data *store;
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stage->privatePtr = MALLOC(sizeof(*store));
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store = FOG_STAGE_DATA(stage);
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if (!store)
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return GL_FALSE;
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_mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
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if (!inited)
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init_static_data();
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return GL_TRUE;
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}
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static void
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free_fog_data(struct tnl_pipeline_stage *stage)
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{
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struct fog_stage_data *store = FOG_STAGE_DATA(stage);
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if (store) {
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_mesa_vector4f_free( &store->fogcoord );
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FREE( store );
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stage->privatePtr = NULL;
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}
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}
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const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
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{
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"build fog coordinates", /* name */
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NULL, /* private_data */
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alloc_fog_data, /* dtr */
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free_fog_data, /* dtr */
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NULL, /* check */
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run_fog_stage /* run -- initially set to init. */
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};
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