/*
* Mesa 3-D graphics library
*
* 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
* THE AUTHORS OR COPYRIGHT HOLDERS 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 "c99_math.h"
#include "main/glheader.h"
#include "main/macros.h"
#include "s_context.h"
#include "s_fog.h"
/**
* Used to convert current raster distance to a fog factor in [0,1].
*/
GLfloat
_swrast_z_to_fogfactor(struct gl_context *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 = expf(-d * z);
f = CLAMP(f, 0.0F, 1.0F);
return f;
case GL_EXP2:
d = ctx->Fog.Density;
f = expf(-(d * d * z * z));
f = CLAMP(f, 0.0F, 1.0F);
return f;
default:
_mesa_problem(ctx, "Bad fog mode in _swrast_z_to_fogfactor");
return 0.0;
}
}
#define LINEAR_FOG(f, coord) f = (fogEnd - coord) * fogScale
#define EXP_FOG(f, coord) f = expf(density * coord)
#define EXP2_FOG(f, coord) \
do { \
GLfloat tmp = negDensitySquared * coord * coord; \
if (tmp < FLT_MIN_10_EXP) \
tmp = FLT_MIN_10_EXP; \
f = expf(tmp); \
} while(0)
#define BLEND_FOG(f, coord) f = coord
/**
* Template code for computing fog blend factor and applying it to colors.
* \param TYPE either GLubyte, GLushort or GLfloat.
* \param COMPUTE_F code to compute the fog blend factor, f.
*/
#define FOG_LOOP(TYPE, FOG_FUNC) \
if (span->arrayAttribs & VARYING_BIT_FOGC) { \
GLuint i; \
for (i = 0; i < span->end; i++) { \
const GLfloat fogCoord = span->array->attribs[VARYING_SLOT_FOGC][i][0]; \
const GLfloat c = fabsf(fogCoord); \
GLfloat f, oneMinusF; \
FOG_FUNC(f, c); \
f = CLAMP(f, 0.0F, 1.0F); \
oneMinusF = 1.0F - f; \
rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog); \
rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog); \
rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog); \
} \
} \
else { \
const GLfloat fogStep = span->attrStepX[VARYING_SLOT_FOGC][0]; \
GLfloat fogCoord = span->attrStart[VARYING_SLOT_FOGC][0]; \
const GLfloat wStep = span->attrStepX[VARYING_SLOT_POS][3]; \
GLfloat w = span->attrStart[VARYING_SLOT_POS][3]; \
GLuint i; \
for (i = 0; i < span->end; i++) { \
const GLfloat c = fabsf(fogCoord) / w; \
GLfloat f, oneMinusF; \
FOG_FUNC(f, c); \
f = CLAMP(f, 0.0F, 1.0F); \
oneMinusF = 1.0F - f; \
rgba[i][RCOMP] = (TYPE) (f * rgba[i][RCOMP] + oneMinusF * rFog); \
rgba[i][GCOMP] = (TYPE) (f * rgba[i][GCOMP] + oneMinusF * gFog); \
rgba[i][BCOMP] = (TYPE) (f * rgba[i][BCOMP] + oneMinusF * bFog); \
fogCoord += fogStep; \
w += wStep; \
} \
}
/**
* Apply fog to a span of RGBA pixels.
* The fog value are either in the span->array->fog array or interpolated from
* the fog/fogStep values.
* They fog values are either fog coordinates (Z) or fog blend factors.
* _PreferPixelFog should be in sync with that state!
*/
void
_swrast_fog_rgba_span( const struct gl_context *ctx, SWspan *span )
{
const SWcontext *swrast = CONST_SWRAST_CONTEXT(ctx);
GLfloat rFog, gFog, bFog;
assert(swrast->_FogEnabled);
assert(span->arrayMask & SPAN_RGBA);
/* compute (scaled) fog color */
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
rFog = ctx->Fog.Color[RCOMP] * 255.0F;
gFog = ctx->Fog.Color[GCOMP] * 255.0F;
bFog = ctx->Fog.Color[BCOMP] * 255.0F;
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
rFog = ctx->Fog.Color[RCOMP] * 65535.0F;
gFog = ctx->Fog.Color[GCOMP] * 65535.0F;
bFog = ctx->Fog.Color[BCOMP] * 65535.0F;
}
else {
rFog = ctx->Fog.Color[RCOMP];
gFog = ctx->Fog.Color[GCOMP];
bFog = ctx->Fog.Color[BCOMP];
}
if (swrast->_PreferPixelFog) {
/* The span's fog values are fog coordinates, now compute blend factors
* and blend the fragment colors with the fog color.
*/
switch (ctx->Fog.Mode) {
case GL_LINEAR:
{
const GLfloat fogEnd = ctx->Fog.End;
const GLfloat fogScale = (ctx->Fog.Start == ctx->Fog.End)
? 1.0F : 1.0F / (ctx->Fog.End - ctx->Fog.Start);
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
GLubyte (*rgba)[4] = span->array->rgba8;
FOG_LOOP(GLubyte, LINEAR_FOG);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
GLushort (*rgba)[4] = span->array->rgba16;
FOG_LOOP(GLushort, LINEAR_FOG);
}
else {
GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
assert(span->array->ChanType == GL_FLOAT);
FOG_LOOP(GLfloat, LINEAR_FOG);
}
}
break;
case GL_EXP:
{
const GLfloat density = -ctx->Fog.Density;
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
GLubyte (*rgba)[4] = span->array->rgba8;
FOG_LOOP(GLubyte, EXP_FOG);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
GLushort (*rgba)[4] = span->array->rgba16;
FOG_LOOP(GLushort, EXP_FOG);
}
else {
GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
assert(span->array->ChanType == GL_FLOAT);
FOG_LOOP(GLfloat, EXP_FOG);
}
}
break;
case GL_EXP2:
{
const GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
GLubyte (*rgba)[4] = span->array->rgba8;
FOG_LOOP(GLubyte, EXP2_FOG);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
GLushort (*rgba)[4] = span->array->rgba16;
FOG_LOOP(GLushort, EXP2_FOG);
}
else {
GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
assert(span->array->ChanType == GL_FLOAT);
FOG_LOOP(GLfloat, EXP2_FOG);
}
}
break;
default:
_mesa_problem(ctx, "Bad fog mode in _swrast_fog_rgba_span");
return;
}
}
else {
/* The span's fog start/step/array values are blend factors in [0,1].
* They were previously computed per-vertex.
*/
if (span->array->ChanType == GL_UNSIGNED_BYTE) {
GLubyte (*rgba)[4] = span->array->rgba8;
FOG_LOOP(GLubyte, BLEND_FOG);
}
else if (span->array->ChanType == GL_UNSIGNED_SHORT) {
GLushort (*rgba)[4] = span->array->rgba16;
FOG_LOOP(GLushort, BLEND_FOG);
}
else {
GLfloat (*rgba)[4] = span->array->attribs[VARYING_SLOT_COL0];
assert(span->array->ChanType == GL_FLOAT);
FOG_LOOP(GLfloat, BLEND_FOG);
}
}
}