AreaLightTest.AreaLightForm.ComputeBRDFIntegral C# (CSharp) Метод

		void	ComputeBRDFIntegral( System.IO.FileInfo _TableFileName0, System.IO.FileInfo _TableFileName1, int _TableSize ) {

			const int		SAMPLES_COUNT_THETA = 128;
			const int		SAMPLES_COUNT_PHI = 2*SAMPLES_COUNT_THETA;

			const double	dTheta = 0.5 * Math.PI / SAMPLES_COUNT_THETA;
			const double	dPhi = 2.0 * Math.PI / SAMPLES_COUNT_PHI;

			double[,]		Table0 = new double[_TableSize,_TableSize];
			double[,]		Table1 = new double[_TableSize,_TableSize];


// float	Theta = 0.5 * _UV.x * PI;
// float3	ToLight = float3( sin( Theta ), 0, cos( Theta ) );
// float3	ToView = float3( -sin( Theta ), 0, cos( Theta ) );
// 
// float	Albedo = 0.0;
// const int	THETA_COUNT = 64; // * $alwaysOne; // warning X4008: floating point division by zero
// const float	dTheta = HALFPI / THETA_COUNT;
// const float	dPhi = TWOPI / THETA_COUNT;
// for ( int i=0; i < THETA_COUNT; i++ )
// {
// 	Theta = HALFPI * (0.5 + i) / THETA_COUNT;
// 	for ( int j=0; j < THETA_COUNT; j++ )
// 	{
// 		float	Phi = PI * j / THETA_COUNT;
// 
// 		ToView = float3( sin( Theta ) * cos( Phi ), sin( Theta ) * sin( Phi ), cos( Theta ) );
// 
// 		float3	Half = normalize( ToLight + ToView );
// 
// 		// "True" and expensive evaluation of the Ward BRDF
// 		float	alpha = Roughness;
// 
// 		float	CosDelta = Half.z;	// dot( Half, _wsNormal );
// 		float	delta = acos( CosDelta );
// 		float	CosThetaL = ToLight.z;
// 		float	SinThetaL = sqrt( 1.0 - CosThetaL*CosThetaL );
// 		float	PhiL = atan2( ToLight.y, ToLight.x );
// 		float	CosThetaV = ToView.z;
// 		float	SinThetaV = sqrt( 1.0 - CosThetaV*CosThetaV );
// 		float	PhiV = atan2( ToView.y, ToView.x );
// 
// 		float	BRDF = 1.0 / square(alpha) * exp( -square( tan( delta ) / alpha ) ) * 2.0 * (1.0 + CosThetaL*CosThetaV + SinThetaL*SinThetaV*cos( PhiV - PhiL )) / pow4( CosThetaL + CosThetaV );
// 
// 		Albedo += BRDF * cos( Theta ) * sin( Theta ) * dTheta * dPhi;
// 	}
// }
// 
// Albedo *= INVPI;	// Since we forgot that in the main loop



			float3	View = new float3();
			float3	Light = new float3();
			for ( int Y=0; Y < _TableSize; Y++ ) {
				float	Roughness = Math.Max( 0.01f, (float) Y / (_TableSize-1) );
				float	r2 = Roughness*Roughness;

				for ( int X=0; X < _TableSize; X++ ) {
//					double	CosThetaV = (double) (1+X) / _TableSize;
//					double	SinThetaV = Math.Sqrt( 1.0 - CosThetaV*CosThetaV );

					double	ThetaV = 0.5 * Math.PI * X / _TableSize;
					double	CosThetaV = Math.Cos( ThetaV );
					double	SinThetaV = Math.Sin( ThetaV );
					View.x = (float) SinThetaV;
					View.y = (float) CosThetaV;
					View.z = 0.0f;

					double	SumA = 0.0;
					double	SumB = 0.0;
					for ( int Theta=0; Theta < SAMPLES_COUNT_THETA; Theta++ ) {
						double	fTheta = 0.5 * Math.PI * (0.5 + Theta) / SAMPLES_COUNT_THETA;
						double	CosThetaL = Math.Cos( fTheta );
						double	SinThetaL = Math.Sin( fTheta );

						// Compute solid angle
						double	SolidAngle = SinThetaL * dTheta * dPhi;
						double	ProjectedSolidAngle = CosThetaL * SolidAngle;	// (N.L) sin(Theta).dTheta.dPhi

						for ( int Phi=0; Phi < SAMPLES_COUNT_PHI; Phi++ ) {
							double	fPhi = Math.PI * Phi / SAMPLES_COUNT_PHI;
							double	CosPhiLight = Math.Cos( fPhi );
							double	SinPhiLight = Math.Sin( fPhi );

							Light.x = (float) (SinPhiLight * SinThetaL);
							Light.y = (float) CosThetaL;
							Light.z = (float) (CosPhiLight * SinThetaL);

// 							// Transform into "reflected-view-centered space"
// 							Light = Light.x * OrthoX + Light.y * ReflectedView + Light.z * OrthoZ;
// 							if ( Light.y < 0.0f )
// 								continue;
// 							ProjectedSolidAngle = dPhi * dTheta * Light.y * Math.Sqrt( 1.0 - Light.y*Light.y );


 							float3	H_unorm = View + Light;
 							float3	H = H_unorm.Normalized;

// 							// Compute normal distribution function
// 							float	H_unorm_dot_N = H_unorm.y;
// 							float	H_unorm_dot_N2 = H_unorm_dot_N * H_unorm_dot_N;
// 							float	H_unorm_dot_N4 = H_unorm_dot_N2 * H_unorm_dot_N2;
// 
// 							double	BRDF = Math.Exp( -(H_unorm.x*H_unorm.x + H_unorm.z*H_unorm.z) / (r2 * H_unorm_dot_N2) ) * H_unorm.Dot( H_unorm ) / H_unorm_dot_N4;

							// Expensive Ward
							double	PhiL = Math.Atan2( Light.z, Light.x );
							double	PhiV = Math.Atan2( View.z, View.x );
							double	tanDelta = Math.Tan( Math.Acos( H.y ) );
							double	BRDF = Math.Exp( -tanDelta*tanDelta / r2 ) * 2.0 * (1.0 + CosThetaL*CosThetaV + SinThetaL*SinThetaV*Math.Cos( PhiV - PhiL )) / Math.Pow( CosThetaL + CosThetaV, 4.0 );


// Try with Unreal's GGX & Smith G term to see if we get the same thing
// double	alpha = r2;
// double	alpha2 = alpha*alpha;
// double	D = alpha2 / (Math.PI * Math.Pow( HoN2*(alpha2 - 1.0) + 1.0, 2.0 ));
// 
// double	k = (Roughness + 1)*(Roughness + 1) / 8.0;
// 
// 		HoN = H_norm.y;
// double	HoL = H_norm.Dot( Light );
// double	HoV = H_norm.Dot( View );
// double	Gl = HoL / (HoL * (1-k) + k);
// double	Gv = HoV / (HoV * (1-k) + k);
// double	G = Gl * Gv;
// 
// double	BRDF = D * G / (4.0 * Light.y * View.y);
// //double	BRDF = D * G * H_norm.Dot( View ) / Math.Max( 1e-6, HoN * View.y);


// Expensive Ward with angles
// double	PhiL = Math.Atan2( Light.z, Light.x );
// double	PhiV = 0.0;//Math.Atan2( View.z, View.x );
// double	tanDelta = Math.Tan( Math.Acos( H_norm.y ) );
// double	BRDF = Math.Exp( -tanDelta*tanDelta / r2 ) * 2.0 * (1.0 + CosThetaLight*CosThetaView + SinThetaLight*SinThetaView*Math.Cos( PhiV - PhiL )) / Math.Pow( CosThetaLight + CosThetaView, 4.0 );
// 
// SumA += BRDF * ProjectedSolidAngle;
// SumB += BRDF * ProjectedSolidAngle;

							// Compute Fresnel terms
							double	VoH = View.x * H.x + View.y * H.y;
							double	Schlick = 1.0 - VoH;
							double	Schlick5 = Schlick * Schlick;
									Schlick5 *= Schlick5 * Schlick;

							double	FresnelA = 1.0 - Schlick5;
							double	FresnelB = Schlick5;

//FresnelA = FresnelB = 1.0;

							SumA += FresnelA * BRDF * ProjectedSolidAngle;
							SumB += FresnelB * BRDF * ProjectedSolidAngle;
						}
					}

					SumA /= Math.PI * r2;
					SumB /= Math.PI * r2;

// 					// For few samples, the sum goes over 1 because we have poor solid angle sampling resolution...
// 					SumA = Math.Min( 1.0, SumA );
// 					SumB = Math.Min( 1.0, SumB );

					Table0[X,Y] = SumA;
					Table1[X,Y] = SumB;
				}
			}

			// Write table 0
			using ( System.IO.FileStream S = _TableFileName0.Create() )
				using ( System.IO.BinaryWriter W = new System.IO.BinaryWriter( S ) )
					for ( int Y=0; Y < _TableSize; Y++ ) {
						for ( int X=0; X < _TableSize; X++ )
							W.Write( Table0[X,Y] );
						}

			// Write table 1
			using ( System.IO.FileStream S = _TableFileName1.Create() )
				using ( System.IO.BinaryWriter W = new System.IO.BinaryWriter( S ) )
					for ( int Y=0; Y < _TableSize; Y++ ) {
						for ( int X=0; X < _TableSize; X++ )
							W.Write( Table1[X,Y] );
						}
		}