SpotEmittance.h

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/* $Id:$ */

#ifndef __SPOT_EMITTANCE_H
#define __SPOT_EMITTANCE_H

#include <esg/emittance/Emittance.h>

/*
 * Emittance attenuating proportionally to spot light parametters.
 */

namespace esg {

class SpotEmittance : public Emittance {
protected:
    float _spreadAngle;    // The angle in rad. between the dir. axis and
                           // a ray  along edge of the cone.
                           // Range is [0.0, PI/2]
    char  _concentration;  // How quickly the light attenuates. Range [0, 128]
    float _cosDelta;       // cosinus of spread angle

protected:
    virtual void _duplicate_attributes (const Emittance& src) {
        Emittance::_duplicate_attributes(src);
        _spreadAngle   = ((SpotEmittance&)src)._spreadAngle;
        _concentration = ((SpotEmittance&)src)._concentration;
        _cosDelta      = ((SpotEmittance&)src)._cosDelta;
    }

    SpotEmittance () {}

public:
    SpotEmittance (const Vector3&  loc,
                   const Vector3&  dir,
                   const Color3f&  inten = Color3f(1,1,1),
                   double          fadeDist      = .0,
                   double          fadePower     = .0,
                   float           spreadAngle   = PI,
                   char            concentration = 0)
        : Emittance(loc, true, dir, true, inten, fadeDist, fadePower),
          _spreadAngle(spreadAngle),
          _concentration(concentration)
    {
        _cosDelta = cos(_spreadAngle);
    }

    virtual Emittance* clone () const {
        SpotEmittance * pRet = new SpotEmittance();
        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 cosGamma = _direction.dot(dir);
        
        if (cosGamma <= _cosDelta) return false; // out of area
        
        c.set(_intensity);
        if (_concentration) c.scale(pow(cosGamma, _concentration));

        ESG_ATTENUATION(d,c);

        return true;
    }

    virtual bool intensity (const Vector3& v /* emittance direction */,
                            float          d /* emittance distance  */,
                            Color3f&       c /* intensity           */) const
    {
        float cosGamma = _direction.dot(v);
        
        if (cosGamma <= _cosDelta) return false; // out of area
        
        c.set(_intensity);
        if (_concentration) c.scale(pow(cosGamma, _concentration));

        ESG_ATTENUATION(d,c);
        
        return true;
    }

    virtual bool stochasticEmission (Vector3& d)
    {
        return false; // to do
    }

    char  concentration (void) const { return _concentration; }
    float spreadAngle   (void) const { return _spreadAngle;   }
};
    
}; // namespace

#endif //__SPOT_EMITTANCE_H

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