/*
* Mesa 3-D graphics library
* Version: 6.5
*
* Copyright (C) 1999-2006 Brian Paul 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 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
* BRIAN PAUL 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/colormac.h"
#include "main/macros.h"
#include "main/imports.h"
#include "main/mtypes.h"
#include "math/m_xform.h"
#include "t_context.h"
#include "t_pipeline.h"
struct fog_stage_data {
GLvector4f fogcoord; /* has actual storage allocated */
};
#define FOG_STAGE_DATA(stage) ((struct fog_stage_data *)stage->privatePtr)
#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];
static GLfloat inited = 0;
#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().
*/
static void
init_static_data( void )
{
GLfloat f = 0.0F;
GLint i = 0;
for ( ; i < FOG_EXP_TABLE_SIZE ; i++, f += FOG_INCR) {
exp_table[i] = EXPF(-f);
}
inited = 1;
}
/**
* 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 that fogcoords may be negative, if eye z is source absolute
* value must be taken earlier.
* Fog blend factors are in the range [0,1].
*/
static void
compute_fog_blend_factors(struct gl_context *ctx, GLvector4f *out, const GLvector4f *in)
{
GLfloat end = ctx->Fog.End;
GLfloat *v = in->start;
GLuint stride = in->stride;
GLuint n = in->count;
GLfloat (*data)[4] = out->data;
GLfloat d;
GLuint i;
out->count = in->count;
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);
for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
const GLfloat z = *v;
GLfloat f = (end - z) * d;
data[i][0] = CLAMP(f, 0.0F, 1.0F);
}
break;
case GL_EXP:
d = ctx->Fog.Density;
for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
const GLfloat z = *v;
NEG_EXP( data[i][0], d * z );
}
break;
case GL_EXP2:
d = ctx->Fog.Density*ctx->Fog.Density;
for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
const GLfloat z = *v;
NEG_EXP( data[i][0], d * z * z );
}
break;
default:
_mesa_problem(ctx, "Bad fog mode in make_fog_coord");
return;
}
}
static GLboolean
run_fog_stage(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
{
TNLcontext *tnl = TNL_CONTEXT(ctx);
struct vertex_buffer *VB = &tnl->vb;
struct fog_stage_data *store = FOG_STAGE_DATA(stage);
GLvector4f *input;
if (!ctx->Fog.Enabled)
return GL_TRUE;
if (ctx->Fog.FogCoordinateSource == GL_FRAGMENT_DEPTH_EXT && !ctx->VertexProgram._Current) {
GLuint i;
GLfloat *coord;
/* Fog is computed from vertex or fragment Z values */
/* source = VB->AttribPtr[_TNL_ATTRIB_POS] or VB->EyePtr coords */
/* dest = VB->AttribPtr[_TNL_ATTRIB_FOG] = fog stage private storage */
VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord;
if (!ctx->_NeedEyeCoords) {
/* compute fog coords from object coords */
const GLfloat *m = ctx->ModelviewMatrixStack.Top->m;
GLfloat plane[4];
/* Use this to store calculated eye z values:
*/
input = &store->fogcoord;
plane[0] = m[2];
plane[1] = m[6];
plane[2] = m[10];
plane[3] = m[14];
/* Full eye coords weren't required, just calculate the
* eye Z values.
*/
_mesa_dotprod_tab[VB->AttribPtr[_TNL_ATTRIB_POS]->size]
( (GLfloat *) input->data,
4 * sizeof(GLfloat),
VB->AttribPtr[_TNL_ATTRIB_POS], plane );
input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
/* make sure coords are really positive
NOTE should avoid going through array twice */
coord = input->start;
for (i = 0; i < input->count; i++) {
*coord = FABSF(*coord);
STRIDE_F(coord, input->stride);
}
}
else {
/* fog coordinates = eye Z coordinates - need to copy for ABS */
input = &store->fogcoord;
if (VB->EyePtr->size < 2)
_mesa_vector4f_clean_elem( VB->EyePtr, VB->Count, 2 );
input->stride = 4 * sizeof(GLfloat);
input->count = VB->EyePtr->count;
coord = VB->EyePtr->start;
for (i = 0 ; i < VB->EyePtr->count; i++) {
input->data[i][0] = FABSF(coord[2]);
STRIDE_F(coord, VB->EyePtr->stride);
}
}
}
else {
/* use glFogCoord() coordinates */
input = VB->AttribPtr[_TNL_ATTRIB_FOG]; /* source data */
/* input->count may be one if glFogCoord was only called once
* before glBegin. But we need to compute fog for all vertices.
*/
input->count = VB->AttribPtr[_TNL_ATTRIB_POS]->count;
VB->AttribPtr[_TNL_ATTRIB_FOG] = &store->fogcoord; /* dest data */
}
if (tnl->_DoVertexFog) {
/* compute blend factors from fog coordinates */
compute_fog_blend_factors( ctx, VB->AttribPtr[_TNL_ATTRIB_FOG], input );
}
else {
/* results = incoming fog coords (compute fog per-fragment later) */
VB->AttribPtr[_TNL_ATTRIB_FOG] = input;
}
return GL_TRUE;
}
/* Called the first time stage->run() is invoked.
*/
static GLboolean
alloc_fog_data(struct gl_context *ctx, struct tnl_pipeline_stage *stage)
{
TNLcontext *tnl = TNL_CONTEXT(ctx);
struct fog_stage_data *store;
stage->privatePtr = MALLOC(sizeof(*store));
store = FOG_STAGE_DATA(stage);
if (!store)
return GL_FALSE;
_mesa_vector4f_alloc( &store->fogcoord, 0, tnl->vb.Size, 32 );
if (!inited)
init_static_data();
return GL_TRUE;
}
static void
free_fog_data(struct tnl_pipeline_stage *stage)
{
struct fog_stage_data *store = FOG_STAGE_DATA(stage);
if (store) {
_mesa_vector4f_free( &store->fogcoord );
FREE( store );
stage->privatePtr = NULL;
}
}
const struct tnl_pipeline_stage _tnl_fog_coordinate_stage =
{
"build fog coordinates", /* name */
NULL, /* private_data */
alloc_fog_data, /* dtr */
free_fog_data, /* dtr */
NULL, /* check */
run_fog_stage /* run -- initially set to init. */
};