BRDFLafortuneFitting.Program.half_diff_coords_to_std_coords C# (CSharp) Method

        static void half_diff_coords_to_std_coords( double _ThetaHalf, double _PhiHalf, double _ThetaDiff, double _PhiDiff,
													ref Vector3 _In, ref Vector3 _Out )
        {
            double	SinTheta_half = Math.Sin( _ThetaHalf );
            Half.Set( Math.Cos( _PhiHalf ) * SinTheta_half, Math.Sin( _PhiHalf ) * SinTheta_half, Math.Cos( _ThetaHalf ) );

            // Build the 2 vectors representing the frame in which we can use the diff angles
            Vector3	OrthoX;
            Half.Cross( ref Normal, out OrthoX );
            if ( OrthoX.LengthSq() < 1e-6 )
                OrthoX.Set( 1, 0, 0 );
            else
                OrthoX.Normalize();

            Vector3	OrthoY;
            Half.Cross( ref OrthoX, out OrthoY );

            // Rotate using diff angles to retrieve incoming direction
            Half.Rotate( ref OrthoX, -_ThetaDiff, out Temp );
            Temp.Rotate( ref Half, _PhiDiff, out _In );

            // ...or by mirroring in "Half tangent space"
            double	MirrorX = -_In.Dot( ref OrthoX );
            double	MirrorY = -_In.Dot( ref OrthoY );
            double	z = _In.Dot( ref Half );
            _Out.Set(
                MirrorX*OrthoX.x + MirrorY*OrthoY.x + z*Half.x,
                MirrorX*OrthoX.y + MirrorY*OrthoY.y + z*Half.y,
                MirrorX*OrthoX.z + MirrorY*OrthoY.z + z*Half.z
            );

            // 			if ( _In.z < -0.5 || _Out.z < -0.5 )
            // 				throw new Exception( "RHA MAIS MERDE!" );
        }