/******************************************************************/
/* LambertianBRDF.cpp                                             */
/* -----------------------                                        */
/*                                                                */
/* 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)                                         */
/******************************************************************/

#include "Materials/LambertianBRDF.h"

Color LambertianBRDF::SampleBRDF( const Ray &r, const Vector &toViewer, const Vector &incidentLight ) const
{   // Lambertian BRDFs are the albedo divided by pi
	return albedo / M_PI;
}

Vector LambertianBRDF::RandomlySelectOutgoingVector( Random *rng, const Vector &normVec ) const
{   // We're sampling our outgoing ray uniformly randomly over the hemisphere
	return rng->RandomHemisphereVector( normVec );
}	

float LambertianBRDF::GetProbabilityOfSampling( const Vector &normVec, const Vector &sampleVec ) const
{   // The probability of sampling is 1/(2pi)
	return 1.0f/(2.0f*M_PI);
}

LambertianBRDF::LambertianBRDF( FILE *f, Scene *s ) : diffuseTexture(0)
{
	albedo = Color::White();

	char buf[ MAXLINELENGTH ], token[256], *ptr;
	while( fgets(buf, MAXLINELENGTH, f) != NULL )  
	{
		ptr = StripLeadingWhiteSpace( buf );             // Find the first token on the line
		if (ptr[0] == '#') continue;                     // Check if it's a comment
		ptr = StripLeadingTokenToBuffer( ptr, token );   // Grab the command to deal with
		MakeLower( token );                              // Make sure it's consistantly lower case
	
		if (!strcmp(token,"end")) break;                 // Done reading the material? 
		if (!strcmp(token,"color") || !strcmp(token,"albedo"))
			albedo = Color( ptr );                       // Read in the albedo
		else
			printf("Error: Unknown command '%s' when loading LambertianBRDF\n", token);
	}

}