#ifndef RIBACKGROUND_H
#define RIBACKGROUND_H

#ifndef RICOMMON_H
#include <RiCommon.H>
#endif

#ifndef RISPECTRUM_H
#include <RiSpectrum.H>
#endif

#ifndef RIVECTOR3_H
#include <RiVector3.H>
#endif

#ifndef RIVECTOR2_H
#include <RiVector2.H>
#endif



/***************************************************************
CLASS
    RiBackground
      Abstraction of all operations needed for a background object.

DESCRIPTION
     All operations needed for a a background object such as returning the
     spectral radiance in a given direction or sampling itself are given.

****************************************************************/

class RiBackground {
  public:
				////
    virtual RiSpectrum GetValue( const RiVector3 &direction ) const = 0;

                                //// Given a seed returns a sample
                                // with prob representing the pdf
                                // with solid angle measure.  Defaults to prob = cos/pi
                                // with z axis "up".
    virtual bool GetSample( const RiVector2 &seed, 
                            RiUnitVector3 &direction,
                            RiReal &prob ) const;

};


class RiConstantBackground : public RiBackground {
   public:
				////
     RiConstantBackground( const RiSpectrum& bg );
				////
     virtual RiSpectrum GetValue( const RiVector3 &direction ) const;
   protected:
				////  The value to be used for the background
     RiSpectrum background;
};

#endif /* RIBACKGROUND_H */