BRDFLafortuneFitting.Program.LookupBRDF C# (CSharp) Method

        static double LookupBRDF( double[] _BRDF, double _ThetaIn, double _PhiIn, double _ThetaOut, double _PhiOut )
        {
            // Convert to half angle / difference angle coordinates
            double ThetaHalf, PhiHalf, ThetaDiff, PhiDiff;
            std_coords_to_half_diff_coords(	_ThetaIn, _PhiIn, _ThetaOut, _PhiOut,
                                            out ThetaHalf, out PhiHalf, out ThetaDiff, out PhiDiff );

            // Find index (note that PhiHalf is ignored, since isotropic BRDFs are assumed)
            int TableIndex = PhiDiff_index( PhiDiff );
                TableIndex += (BRDF_SAMPLING_RES_PHI_D / 2) * ThetaDiff_index( ThetaDiff );
                TableIndex += (BRDF_SAMPLING_RES_THETA_D*BRDF_SAMPLING_RES_PHI_D / 2) * ThetaHalf_index( ThetaHalf );

            double	Result = _BRDF[TableIndex];
            //					Result *= _ComponentScale;
            return Result;
        }