/******************************************************************/
/* LambertianBRDF.h                                               */
/* -----------------------                                        */
/*                                                                */
/* Defines a very simple Lambertian BRDF material type that you   */
/*    can use with the BRDFMaterial class to get simple diffuse   */
/*    surfaces.                                                   */
/*                                                                */
/* Chris Wyman (4/9/2006)                                         */
/******************************************************************/


#ifndef LAMBERTIANBRDF_H
#define LAMBERTIANBRDF_H

#include "DataTypes/Color.h"
#include "DataTypes/Vector.h"
#include "DataTypes/Texture.h"
#include "Utils/TextParsing.h"
#include "Utils/Random.h"
#include "Materials/BRDF.h"


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

class Scene;

class LambertianBRDF : public BRDF {
	Color albedo;
public:
	LambertianBRDF() : albedo(Color::White()) {}
	LambertianBRDF( FILE *f, Scene *s );

	// This function returns the BRDF given the directions to the viewer and to the light.  The ray structure
	//    can be used to get information about the hitpoint, and perhaps other relevent information, e.g. the
	//    surface parameterization
	virtual Color  SampleBRDF( const Ray &r, const Vector &toViewer, const Vector &incidentLight ) const;

	// This function returns a random vector sampled (somehow) over the hemisphere
	virtual Vector RandomlySelectOutgoingVector( Random *rng, const Vector &normVec ) const;

	// Given the random vector from above, return the probability of selecting this vector.
	//    NOTE: One could consider incorporating this function with RandomlySelectOutgoingVector, by
	//          returning the probability in an additional parameter.  That is a little less clean,
	//          but it probably eliminates duplicate computations that would be needed for the 
	//          GetProbabilityOfSampling method with more complex sampling schemes.
	virtual float  GetProbabilityOfSampling( const Vector &normVec, const Vector &sampleVec ) const;

};




#endif