StelToneReproducer.hpp

/*
 * Copyright (C) 2003 Fabien Chereau
 *
 * 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., 51 Franklin Street, Suite 500, Boston, MA  02110-1335, USA.
 */

#ifndef _STELTONEREPRODUCER_HPP_
#define _STELTONEREPRODUCER_HPP_

#include <QDebug>


class StelToneReproducer
{
public:
    StelToneReproducer();
    
    virtual ~StelToneReproducer();

    void setDisplayAdaptationLuminance(float displayAdaptationLuminance);

    void setWorldAdaptationLuminance(float worldAdaptationLuminance);
    float getWorldAdaptationLuminance() const {return Lwa;}
    
    void setInputScale(float scale=1.f);
    float getInputScale() const {return inputScale;}
    
    void setMaxDisplayLuminance(float maxdL)
    {oneOverMaxdL = 1.f/maxdL; lnOneOverMaxdL=std::log(oneOverMaxdL); term2TimesOneOverMaxdLpOneOverGamma = std::pow(term2*oneOverMaxdL, oneOverGamma);}

    float getDisplayGamma() const {return 1.f/oneOverGamma;}
    
    void setDisplayGamma(float gamma)
    {oneOverGamma = 1.f/gamma; term2TimesOneOverMaxdLpOneOverGamma = std::pow(term2*oneOverMaxdL, oneOverGamma);}

    float adaptLuminance(float worldLuminance) const
    {
        return std::pow((float)(inputScale*worldLuminance*M_PI*0.0001f),alphaWaOverAlphaDa) * term2;
    }

    float reverseAdaptLuminance(float displayLuminance) const
    {
        return std::pow((float)(displayLuminance/term2),1.f/alphaWaOverAlphaDa)/(inputScale*M_PI*0.0001f);
    }
    
    float adaptLuminanceScaled(float worldLuminance) const
    {
        return adaptLuminance(worldLuminance)*oneOverMaxdL;
    }
    
    float reverseAdaptLuminanceScaled(float displayLuminance) const
    {
        return reverseAdaptLuminance(displayLuminance/oneOverMaxdL);
    }
    
    float adaptLuminanceScaledLn(float lnWorldLuminance, float pFact=0.5f) const
    {
        const float lnPix0p0001 = -8.0656104861f;
        //Needs better name
        const float temp        = ((lnInputScale + lnWorldLuminance + lnPix0p0001) * 
                                    alphaWaOverAlphaDa+lnTerm2 + lnOneOverMaxdL) * pFact;

        // Optimization:
        // Always using exp here takes 6-9% of runtime in release mode.
        // This code is used to determine point source radius.
        //
        // If this value is < 5 (and < 4, for that matter), the star won't 
        // even be displayed as it's radius is too low. We also get rid 
        // of ~90% of exp calls.
        if(temp < -5.0f)
        {
            return 0.0f;
        }

        return std::exp(temp);
    }
    
    void xyYToRGB(float* xyY) const;
    
    void getShadersParams(float& a, float& b, float & c) const
    {
        a=alphaWaOverAlphaDa;
        b=oneOverGamma;
        c=term2TimesOneOverMaxdLpOneOverGamma;
    }
private:
    // The global luminance scaling
    float inputScale;
    float lnInputScale;     // std::log(inputScale)
    
    float Lda;      // Display luminance adaptation (in cd/m^2)
    float Lwa;      // World   luminance adaptation (in cd/m^2)
    float oneOverMaxdL; // 1 / Display maximum luminance (in cd/m^2)
    float lnOneOverMaxdL; // log(oneOverMaxdL)
    float oneOverGamma; // 1 / Screen gamma value

    // Precomputed variables
    float alphaDa;
    float betaDa;
    float alphaWa;
    float betaWa;
    float alphaWaOverAlphaDa;
    float term2;
    float lnTerm2;  // log(term2)
    
    float term2TimesOneOverMaxdLpOneOverGamma;
};

#endif // _STELTONEREPRODUCER_HPP_