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* Copyright (C) 2003 Fabien Chereau
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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// Class which compute and display the daylight sky color using openGL
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// the sky is computed with the Skylight class.
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// TODO : Adaptative resolution for optimization
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#include "stellarium.h"
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#include "stel_utility.h"
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#include "stellastro.h"
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#include "stel_atmosphere.h"
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Atmosphere::Atmosphere() : sky_resolution(48), tab_sky(NULL), world_adaptation_luminance(0.f), atm_intensity(0)
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// Create the vector array used to store the sky color on the full field of view
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tab_sky = new Vec3f*[sky_resolution+1];
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for (int k=0; k<sky_resolution+1 ;k++)
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tab_sky[k] = new Vec3f[sky_resolution+1];
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Atmosphere::~Atmosphere()
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for (int k=0; k<sky_resolution+1 ;k++)
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if (tab_sky[k]) delete [] tab_sky[k];
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if (tab_sky) delete [] tab_sky;
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void Atmosphere::compute_color(double JD, Vec3d sunPos, Vec3d moonPos, float moon_phase,
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ToneReproductor * eye, Projector* prj,
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float latitude, float altitude, float temperature, float relative_humidity)
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float min_mw_lum = 0.13;
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// no need to calculate if not visible
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if(!fader.getInterstate())
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world_adaptation_luminance = 3.75f;
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milkyway_adaptation_luminance = min_mw_lum; // brighter than without atm, since no drawing addition of atm brightness
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atm_intensity = fader.getInterstate();
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// these are for radii
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double sun_angular_size = atan(696000./AU/sunPos.length());
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double moon_angular_size = atan(1738./AU/moonPos.length());
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double touch_angle = sun_angular_size + moon_angular_size;
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double dark_angle = moon_angular_size - sun_angular_size;
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// determine luminance falloff during solar eclipses
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double separation_angle = acos( sunPos.dot( moonPos )); // angle between them
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// printf("touch at %f\tnow at %f (%f)\n", touch_angle, separation_angle, separation_angle/touch_angle);
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// bright stars should be visible at total eclipse
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// TODO: correct for atmospheric diffusion
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// TODO: use better coverage function (non-linear)
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// because of above issues, this algorithm darkens more quickly than reality
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if( separation_angle < touch_angle)
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float asun = sun_angular_size*sun_angular_size;
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min = (asun - moon_angular_size*moon_angular_size)/asun; // minimum proportion of sun uncovered
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else min = 0.004; // so bright stars show up at total eclipse
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if(separation_angle < dark_angle) atm_intensity = min;
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else atm_intensity *= min + (1.-min)*(separation_angle-dark_angle)/(touch_angle-dark_angle);
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// printf("atm int %f (min %f)\n", atm_intensity, min);
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sun_pos[0] = sunPos[0];
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sun_pos[1] = sunPos[1];
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sun_pos[2] = sunPos[2];
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moon_pos[0] = moonPos[0];
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moon_pos[1] = moonPos[1];
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moon_pos[2] = moonPos[2];
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sky.set_paramsv(sun_pos, 5.f);
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skyb.set_loc(latitude * M_PI/180., altitude, temperature, relative_humidity);
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skyb.set_sun_moon(moon_pos[2], sun_pos[2]);
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// Calculate the date from the julian day.
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skyb.set_date(date.years, date.months, moon_phase);
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float stepX = (float)prj->getViewportWidth() / sky_resolution;
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float stepY = (float)prj->getViewportHeight() / sky_resolution;
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float viewport_left = (float)prj->getViewportPosX();
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float viewport_bottom = (float)prj->getViewportPosY();
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Vec3d point(1., 0., 0.);
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// Variables used to compute the average sky luminance
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unsigned int nb_lum = 0;
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// Compute the sky color for every point above the ground
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for (int x=0; x<=sky_resolution; ++x)
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for(int y=0; y<=sky_resolution; ++y)
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prj->unproject_local((double)viewport_left+x*stepX, (double)viewport_bottom+y*stepY,point);
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point[2] = -point[2];
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// The sky below the ground is the symetric of the one above :
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// it looks nice and gives proper values for brightness estimation
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b2.pos[0] = point[0];
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b2.pos[1] = point[1];
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b2.pos[2] = point[2];
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// Use the Skylight model for the color
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sky.get_xyY_valuev(b2);
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// Use the Skybright.cpp 's models for brightness which gives better results.
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b2.color[2] = skyb.get_luminance(moon_pos[0]*b2.pos[0]+moon_pos[1]*b2.pos[1]+
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moon_pos[2]*b2.pos[2], sun_pos[0]*b2.pos[0]+sun_pos[1]*b2.pos[1]+
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sun_pos[2]*b2.pos[2], b2.pos[2]);
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sum_lum+=b2.color[2];
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eye->xyY_to_RGB(b2.color);
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tab_sky[x][y].set(atm_intensity*b2.color[0],atm_intensity*b2.color[1],atm_intensity*b2.color[2]);
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world_adaptation_luminance = 3.75f + 3.5*sum_lum/nb_lum*atm_intensity;
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milkyway_adaptation_luminance = min_mw_lum*(1-atm_intensity) + 30*sum_lum/nb_lum*atm_intensity;
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// Draw the atmosphere using the precalc values stored in tab_sky
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void Atmosphere::draw(Projector* prj, int delta_time)
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if(fader.getInterstate())
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// printf("Atm int: %f\n", atm_intensity);
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glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_COLOR);
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float stepX = (float)prj->getViewportWidth() / sky_resolution;
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float stepY = (float)prj->getViewportHeight() / sky_resolution;
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float viewport_left = (float)prj->getViewportPosX();
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float view_bottom = (float)prj->getViewportPosY();
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glDisable(GL_TEXTURE_2D);
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prj->set_orthographic_projection(); // set 2D coordinate
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for (int y2=0; y2<sky_resolution; ++y2)
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glBegin(GL_QUAD_STRIP);
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for(int x2=0; x2<sky_resolution+1; ++x2)
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glColor3fv(tab_sky[x2][y2]);
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glVertex2i((int)(viewport_left+x2*stepX),(int)(view_bottom+y2*stepY));
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glColor3fv(tab_sky[x2][y2+1]);
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glVertex2i((int)(viewport_left+x2*stepX),(int)(view_bottom+(y2+1)*stepY));
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prj->reset_perspective_projection();
added
removed
src/stel_atmosphere.cpp
