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OS/2 Shareware BBS: 10 Tools
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mesa5.zip
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mesa5src.zip
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swrast
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s_fog.cpp
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2002-08-06
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/* $Id: s_fog.c,v 1.23 2002/08/07 00:45:07 brianp Exp $ */
/*
* Mesa 3-D graphics library
* Version: 4.1
*
* Copyright (C) 1999-2002 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.
*/
#include "glheader.h"
#include "colormac.h"
#include "context.h"
#include "macros.h"
#include "mmath.h"
#include "s_context.h"
#include "s_fog.h"
#include "s_span.h"
/**
* Used to convert current raster distance to a fog factor in [0,1].
*/
GLfloat
_mesa_z_to_fogfactor(GLcontext *ctx, GLfloat z)
{
GLfloat d, f;
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);
f = (ctx->Fog.End - z) * d;
return CLAMP(f, 0.0F, 1.0F);
case GL_EXP:
d = ctx->Fog.Density;
f = (GLfloat) exp(-d * z);
return f;
case GL_EXP2:
d = ctx->Fog.Density;
f = (GLfloat) exp(-(d * d * z * z));
return f;
default:
_mesa_problem(ctx, "Bad fog mode in _mesa_z_to_fogfactor");
return 0.0;
}
}
/**
* Calculate fog factors (in [0,1]) from window z values
* Input: n - number of pixels
* z - array of integer depth values
* red, green, blue, alpha - pixel colors
* Output: red, green, blue, alpha - fogged pixel colors
*
* Use lookup table & interpolation?
*/
static void
compute_fog_factors_from_z( const GLcontext *ctx,
GLuint n,
const GLdepth z[],
GLfloat fogFact[] )
{
const GLfloat *proj = ctx->ProjectionMatrixStack.Top->m;
const GLboolean ortho = (proj[15] != 0.0F);
const GLfloat p10 = proj[10];
const GLfloat p14 = proj[14];
const GLfloat tz = ctx->Viewport._WindowMap.m[MAT_TZ];
GLfloat szInv;
GLuint i;
if (ctx->Viewport._WindowMap.m[MAT_SZ] == 0.0)
szInv = 1.0F;
else
szInv = 1.0F / ctx->Viewport._WindowMap.m[MAT_SZ];
/*
* Note: to compute eyeZ from the ndcZ we have to solve the following:
*
* p[10] * eyeZ + p[14] * eyeW
* ndcZ = ---------------------------
* p[11] * eyeZ + p[15] * eyeW
*
* Thus:
*
* p[14] * eyeW - p[15] * eyeW * ndcZ
* eyeZ = ----------------------------------
* p[11] * ndcZ - p[10]
*
* If we note:
* a) if using an orthographic projection, p[11] = 0 and p[15] = 1.
* b) if using a perspective projection, p[11] = -1 and p[15] = 0.
* c) we assume eyeW = 1 (not always true- glVertex4)
*
* Then we can simplify the calculation of eyeZ quite a bit. We do
* separate calculations for the orthographic and perspective cases below.
* Note that we drop a negative sign or two since they don't matter.
*/
switch (ctx->Fog.Mode) {
case GL_LINEAR:
{
GLfloat fogEnd = ctx->Fog.End;
GLfloat fogScale;
if (ctx->Fog.Start == ctx->Fog.End)
fogScale = 1.0;
else
fogScale = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
if (ortho) {
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = (ndcz - p14) / p10;
GLfloat f;
if (eyez < 0.0)
eyez = -eyez;
f = (fogEnd - eyez) * fogScale;
fogFact[i] = CLAMP(f, 0.0F, 1.0F);
}
}
else {
/* perspective */
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = p14 / (ndcz + p10);
GLfloat f;
if (eyez < 0.0)
eyez = -eyez;
f = (fogEnd - eyez) * fogScale;
fogFact[i] = CLAMP(f, 0.0F, 1.0F);
}
}
}
break;
case GL_EXP:
if (ortho) {
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = (ndcz - p14) / p10;
if (eyez < 0.0)
eyez = -eyez;
fogFact[i] = (GLfloat) exp( -ctx->Fog.Density * eyez );
}
}
else {
/* perspective */
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = p14 / (ndcz + p10);
if (eyez < 0.0)
eyez = -eyez;
fogFact[i] = (GLfloat) exp( -ctx->Fog.Density * eyez );
}
}
break;
case GL_EXP2:
{
GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
if (ortho) {
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = (ndcz - p14) / p10;
GLfloat tmp = negDensitySquared * eyez * eyez;
#if defined(__alpha__) || defined(__alpha)
/* XXX this underflow check may be needed for other systems*/
if (tmp < FLT_MIN_10_EXP)
tmp = FLT_MIN_10_EXP;
#endif
fogFact[i] = (GLfloat) exp( tmp );
}
}
else {
/* perspective */
for (i=0;i<n;i++) {
GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
GLfloat eyez = p14 / (ndcz + p10);
GLfloat tmp = negDensitySquared * eyez * eyez;
#if defined(__alpha__) || defined(__alpha)
/* XXX this underflow check may be needed for other systems*/
if (tmp < FLT_MIN_10_EXP)
tmp = FLT_MIN_10_EXP;
#endif
fogFact[i] = (GLfloat) exp( tmp );
}
}
}
break;
default:
_mesa_problem(ctx, "Bad fog mode in compute_fog_factors_from_z");
return;
}
}
/**
* Apply fog to a span of RGBA pixels.
* The fog factors are either in the span->array->fog or stored as base/step.
* These are fog _factors_, not fog coords. Fog coords were converted to
* fog factors per vertex.
*/
void
_mesa_fog_rgba_span( const GLcontext *ctx, struct sw_span *span )
{
const SWcontext *swrast = SWRAST_CONTEXT(ctx);
const GLuint n = span->end;
GLchan (*rgba)[4] = (GLchan (*)[4]) span->array->rgba;
GLchan rFog, gFog, bFog;
ASSERT(ctx->Fog.Enabled);
ASSERT((span->interpMask | span->arrayMask) & SPAN_FOG);
ASSERT(span->arrayMask & SPAN_RGBA);
UNCLAMPED_FLOAT_TO_CHAN(rFog, ctx->Fog.Color[RCOMP]);
UNCLAMPED_FLOAT_TO_CHAN(gFog, ctx->Fog.Color[GCOMP]);
UNCLAMPED_FLOAT_TO_CHAN(bFog, ctx->Fog.Color[BCOMP]);
if (swrast->_PreferPixelFog) {
/* compute fog factor from each fragment's Z value */
if ((span->interpMask & SPAN_Z) && (span->arrayMask & SPAN_Z) == 0)
_mesa_span_interpolate_z(ctx, span);
compute_fog_factors_from_z(ctx, n, span->array->z, span->array->fog);
span->arrayMask |= SPAN_FOG;
}
if (span->arrayMask & SPAN_FOG) {
/* use fog array in span */
GLuint i;
for (i = 0; i < n; i++) {
const GLfloat fog = span->array->fog[i];
const GLfloat oneMinusFog = 1.0F - fog;
rgba[i][RCOMP] = (GLchan) (fog * rgba[i][RCOMP] + oneMinusFog * rFog);
rgba[i][GCOMP] = (GLchan) (fog * rgba[i][GCOMP] + oneMinusFog * gFog);
rgba[i][BCOMP] = (GLchan) (fog * rgba[i][BCOMP] + oneMinusFog * bFog);
}
}
else {
/* interpolate fog factors */
GLfloat fog = span->fog, dFog = span->fogStep;
GLuint i;
for (i = 0; i < n; i++) {
const GLfloat oneMinusFog = 1.0F - fog;
rgba[i][RCOMP] = (GLchan) (fog * rgba[i][RCOMP] + oneMinusFog * rFog);
rgba[i][GCOMP] = (GLchan) (fog * rgba[i][GCOMP] + oneMinusFog * gFog);
rgba[i][BCOMP] = (GLchan) (fog * rgba[i][BCOMP] + oneMinusFog * bFog);
fog += dFog;
}
}
}
/**
* As above, but color index mode.
*/
void
_mesa_fog_ci_span( const GLcontext *ctx, struct sw_span *span )
{
const SWcontext *swrast = SWRAST_CONTEXT(ctx);
const GLuint n = span->end;
GLuint *index = span->array->index;
ASSERT(ctx->Fog.Enabled);
ASSERT(span->arrayMask & SPAN_INDEX);
ASSERT((span->interpMask | span->arrayMask) & SPAN_FOG);
if (swrast->_PreferPixelFog) {
/* compute fog factor from each fragment's Z value */
if ((span->interpMask & SPAN_Z) && (span->arrayMask & SPAN_Z) == 0)
_mesa_span_interpolate_z(ctx, span);
compute_fog_factors_from_z(ctx, n, span->array->z, span->array->fog);
span->arrayMask |= SPAN_FOG;
}
if (span->arrayMask & SPAN_FOG) {
const GLuint idx = (GLuint) ctx->Fog.Index;
GLuint i;
for (i = 0; i < n; i++) {
const GLfloat f = CLAMP(span->array->fog[i], 0.0F, 1.0F);
index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * idx);
}
}
else {
GLfloat fog = span->fog, dFog = span->fogStep;
const GLuint idx = (GLuint) ctx->Fog.Index;
GLuint i;
for (i = 0; i < n; i++) {
const GLfloat f = CLAMP(fog, 0.0F, 1.0F);
index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * idx);
fog += dFog;
}
}
}