flightgear/src/Time/light.cxx

//
// light.cxx -- lighting routines
//
// Written by Curtis Olson, started April 1998.
//
// Copyright (C) 1998  Curtis L. Olson  - curt@me.umn.edu
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#ifdef HAVE_WINDOWS_H
#  include <windows.h>
#endif

#include <GL/gl.h>

#include <simgear/compiler.h>

#ifdef SG_MATH_EXCEPTION_CLASH
#  define exception c_exception
#endif

#ifdef SG_HAVE_STD_INCLUDES
#  include <cmath>
#else
#  include <math.h>
#endif

#include <string>
SG_USING_STD(string);

#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/math/interpolater.hxx>
#include <simgear/math/polar3d.hxx>
#include <simgear/misc/sg_path.hxx>
#include <simgear/scene/sky/sky.hxx>
#include <simgear/screen/colors.hxx>

#include <Main/main.hxx>
#include <Main/globals.hxx>
#include <Main/fg_props.hxx>
#include <Main/viewer.hxx>

#include "light.hxx"
#include "sunpos.hxx"

fgLIGHT cur_light_params;


// Constructor
fgLIGHT::fgLIGHT( void ) {
}


// initialize lighting tables
void fgLIGHT::Init( void ) {
    SG_LOG( SG_EVENT, SG_INFO, 
	    "Initializing Lighting interpolation tables." );

    // build the path name to the ambient lookup table
    SGPath path( globals->get_fg_root() );
    SGPath ambient = path;
    ambient.append( "Lighting/ambient" );
    SGPath diffuse = path;
    diffuse.append( "Lighting/diffuse" );
    SGPath specular = path;
    specular.append( "Lighting/specular" );
    SGPath sky = path;
    sky.append( "Lighting/sky" );

    // initialize ambient table
    ambient_tbl = new SGInterpTable( ambient.str() );

    // initialize diffuse table
    diffuse_tbl = new SGInterpTable( diffuse.str() );
    
    // initialize diffuse table
    specular_tbl = new SGInterpTable( specular.str() );
    
    // initialize sky table
    sky_tbl = new SGInterpTable( sky.str() );
}


// update lighting parameters based on current sun position
void fgLIGHT::Update( void ) {
    // if the 4th field is 0.0, this specifies a direction ...
    GLfloat white[4] = { 1.0, 1.0, 1.0, 1.0 };
    // base sky color
    GLfloat base_sky_color[4] = { 0.39, 0.50, 0.74, 1.0 };
    // base fog color
    GLfloat base_fog_color[4] = { 0.84, 0.87, 1.0, 1.0 };
    float deg, ambient, diffuse, specular, sky_brightness;

    SG_LOG( SG_EVENT, SG_INFO, "Updating light parameters." );

    // calculate lighting parameters based on sun's relative angle to
    // local up

    deg = sun_angle * SGD_RADIANS_TO_DEGREES;
    SG_LOG( SG_EVENT, SG_INFO, "  Sun angle = " << deg );

    ambient = ambient_tbl->interpolate( deg );
    diffuse = diffuse_tbl->interpolate( deg );
    specular = specular_tbl->interpolate( deg );
    sky_brightness = sky_tbl->interpolate( deg );

    SG_LOG( SG_EVENT, SG_INFO, 
	    "  ambient = " << ambient << "  diffuse = " << diffuse 
	    << "  specular = " << specular << "  sky = " << sky_brightness );

    // sky_brightness = 0.15;  // used to force a dark sky (when testing)

    // if ( ambient < 0.02 ) { ambient = 0.02; }
    // if ( diffuse < 0.0 ) { diffuse = 0.0; }
    // if ( sky_brightness < 0.1 ) { sky_brightness = 0.1; }

    // set sky color
    sky_color[0] = base_sky_color[0] * sky_brightness;
    sky_color[1] = base_sky_color[1] * sky_brightness;
    sky_color[2] = base_sky_color[2] * sky_brightness;
    sky_color[3] = base_sky_color[3];
    gamma_correct_rgb( sky_color );

    // set cloud and fog color
    cloud_color[0] = fog_color[0] = base_fog_color[0] * sky_brightness;
    cloud_color[1] = fog_color[1] = base_fog_color[1] * sky_brightness;
    cloud_color[2] = fog_color[2] = base_fog_color[2] * sky_brightness;
    cloud_color[3] = fog_color[3] = base_fog_color[3];
    gamma_correct_rgb( fog_color );

    // adjust the cloud colors for sunrise/sunset effects (darken them)
    if (sun_angle > 1.0) {
       float sun2 = sqrt(sun_angle);
       cloud_color[0] /= sun2;
       cloud_color[1] /= sun2;
       cloud_color[2] /= sun2;
    }
    gamma_correct_rgb( cloud_color );

    if (fgGetBool("/test/scene_lighting")) {
        float *sun_color = thesky->get_sun_color();

        scene_ambient[0] = ((sun_color[0]*0.25 + cloud_color[0]*0.75) + ambient) / 2;
        scene_ambient[1] = ((sun_color[1]*0.25 + cloud_color[1]*0.75) + ambient) / 2;
        scene_ambient[2] = ((sun_color[2]*0.25 + cloud_color[2]*0.75) + ambient) / 2;
        // scene_ambient[0] = white[0] * ambient;
        // scene_ambient[1] = white[0] * ambient;
        // scene_ambient[2] = white[0] * ambient;
        scene_ambient[3] = 1.0;

        scene_diffuse[0] = (sun_color[0]*0.25 + fog_color[0]*0.75) * diffuse;
        scene_diffuse[1] = (sun_color[1]*0.25 + fog_color[1]*0.75) * diffuse;
        scene_diffuse[2] = (sun_color[2]*0.25 + fog_color[2]*0.75) * diffuse;
        scene_diffuse[3] = 1.0;

        scene_specular[0] = sun_color[0] * specular;
        scene_specular[1] = sun_color[1] * specular;
        scene_specular[2] = sun_color[2] * specular;
        scene_specular[3] = 1.0;

    } else {

        scene_ambient[0] = white[0] * ambient;
        scene_ambient[1] = white[1] * ambient;
        scene_ambient[2] = white[2] * ambient;
        scene_ambient[3] = 1.0;

        scene_diffuse[0] = white[0] * diffuse;
        scene_diffuse[1] = white[1] * diffuse;
        scene_diffuse[2] = white[2] * diffuse;
        scene_diffuse[3] = 1.0;
        
        scene_specular[0] = white[0] * ambient;
        scene_specular[1] = white[1] * ambient;
        scene_specular[2] = white[2] * ambient;
        scene_specular[3] = 1.0;
    }
}


// calculate fog color adjusted for sunrise/sunset effects
void fgLIGHT::UpdateAdjFog( void ) {

    double heading = globals->get_current_view()->getHeading_deg()
                     * SGD_DEGREES_TO_RADIANS;
    double heading_offset = globals->get_current_view()->getHeadingOffset_deg()
                            * SGD_DEGREES_TO_RADIANS;

    SG_LOG( SG_EVENT, SG_DEBUG, "Updating adjusted fog parameters." );

    // set fog color (we'll try to match the sunset color in the
    // direction we are looking

    // Do some sanity checking ...
    if ( sun_rotation < -2.0 * SGD_2PI || sun_rotation > 2.0 * SGD_2PI ) {
	SG_LOG( SG_EVENT, SG_ALERT, "Sun rotation bad = " << sun_rotation );
	exit(-1);
    }

    if ( heading < -2.0 * SGD_2PI || heading > 2.0 * SGD_2PI ) {
	SG_LOG( SG_EVENT, SG_ALERT, "Heading rotation bad = " << heading );
	exit(-1);
    }

    if ( heading_offset < -2.0 * SGD_2PI || heading_offset > 2.0 * SGD_2PI ) {
	SG_LOG( SG_EVENT, SG_ALERT, "Heading offset bad = " << heading_offset );
	exit(-1);
    }

    double rotation;

    // first determine the difference between our view angle and local
    // direction to the sun
    rotation = -(sun_rotation + SGD_PI) - heading + heading_offset;
    while ( rotation < 0 ) {
	rotation += SGD_2PI;
    }
    while ( rotation > SGD_2PI ) {
	rotation -= SGD_2PI;
    }

    // revert to unmodified values before usign them.
    //
    float *sun_color = thesky->get_sun_color();

    gamma_restore_rgb( fog_color );

    // Calculate the fog color in the direction of the sun for
    // sunrise/sunset effects.
    //
    float s_red =   (fog_color[0] + 2 * sun_color[0]*sun_color[0]) / 3;
    float s_green = (fog_color[1] + 2 * sun_color[1]*sun_color[1]) / 3;
    float s_blue =  (fog_color[2] + 2 * sun_color[2]) / 3;

    // interpolate beween the sunrise/sunset color and the color
    // at the opposite direction of this effect. Take in account
    // the current visibility.
    //
    float av = thesky->get_visibility();
    if (av > 45000)
       av = 45000;

    float avf = 0.87 - (45000 - av) / 83333.33;
    float sif = 0.5 - cos(sun_angle*2)/2;

    float rf1 = fabs((rotation - SGD_PI) / SGD_PI);             // 0.0 .. 1.0
    float rf2 = avf * pow(rf1 * rf1, 1/sif);
    float rf3 = 0.94 - rf2;

    adj_fog_color[0] = rf3 * fog_color[0] + rf2 * s_red;
    adj_fog_color[1] = rf3 * fog_color[1] + rf2 * s_green;
    adj_fog_color[2] = rf3 * fog_color[2] + rf2 * s_blue;
    gamma_correct_rgb( adj_fog_color );

    // make sure the colors have their original value before they are being
    // used by the rest of the program.
    //
    gamma_correct_rgb( fog_color );
}


// Destructor
fgLIGHT::~fgLIGHT( void ) {
}