DirEmittance.h

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/* $Id:$ */

#ifndef __DIR_EMITTANCE_H
#define __DIR_EMITTANCE_H

#include <esg/emittance/Emittance.h>
#include <esg/geometry/Hemisphere.h>
#include <esg/Definitions.h>

/*
 * Emittance radiating from single point towards half-space defined
 * by directional vector and proportionally to the elevation angle.
 */

namespace esg {

class DirEmittance : public Emittance {
protected:
    const Hemisphere _stochasticEmitter;
    
protected:
    virtual void _duplicate_attributes (const Emittance& src) {
        Emittance::_duplicate_attributes(src);
    }

    DirEmittance () {}
    
public:
    DirEmittance (const Vector3&  loc,
                  const Vector3&  dir,
                  const Color3f&  inten = Color3f(1,1,1),
                  double          fadeDist  = .0,
                  double          fadePower = .0)
        : Emittance(loc, true, dir, true, inten, fadeDist, fadePower),
          _stochasticEmitter(Vector3(0.,0.,0.), 1., dir, false) {}

    virtual Emittance* clone () const {
        DirEmittance * pRet = new DirEmittance();
        pRet->_duplicate_attributes(*this);
        return pRet;
    }

    virtual bool intensity (const Vector3& v /* view point */,
                            Color3f&       c /* intensity  */) const
    {
        Vector3 dir(v - _location);
        float   d = dir.length();
        dir.scale(1.0/d);
        float cos = _direction.dot(dir);
        if (cos <= 0.) return false;
        c.set(_intensity);
        c.scale(cos);
        ESG_ATTENUATION(d,c);
        return true;
    }

    virtual bool intensity (const Vector3& v /* emittance direction */,
                            float          d /* emittance distance  */,
                            Color3f&       c /* intensity           */) const
    {
        float cos = _direction.dot(v);
        if (cos <= 0.) return false;
        c.set(_intensity);
        c.scale(cos);
        ESG_ATTENUATION(d,c);
        return true;
    }

    virtual bool stochasticEmission (Vector3& d) 
    {
        d.set(_stochasticEmitter.samplePriorToZenith(ESG_DBL_RAND,
                                                     ESG_DBL_RAND,
                                                     NULL));
        return true;
    }
};
    
}; // namespace

#endif // __DIR_EMITTANCE_H

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