00001 /*************************************************************************** 00002 * Copyright (C) 1998-2008 by authors (see AUTHORS.txt ) * 00003 * * 00004 * This file is part of LuxRender. * 00005 * * 00006 * Lux Renderer is free software; you can redistribute it and/or modify * 00007 * it under the terms of the GNU General Public License as published by * 00008 * the Free Software Foundation; either version 3 of the License, or * 00009 * (at your option) any later version. * 00010 * * 00011 * Lux Renderer is distributed in the hope that it will be useful, * 00012 * but WITHOUT ANY WARRANTY; without even the implied warranty of * 00013 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * 00014 * GNU General Public License for more details. * 00015 * * 00016 * You should have received a copy of the GNU General Public License * 00017 * along with this program. If not, see <http://www.gnu.org/licenses/>. * 00018 * * 00019 * This project is based on PBRT ; see http://www.pbrt.org * 00020 * Lux Renderer website : http://www.luxrender.net * 00021 ***************************************************************************/ 00022 00023 // blinn.cpp* 00024 #include "blinn.h" 00025 #include "color.h" 00026 #include "spectrum.h" 00027 #include "mc.h" 00028 #include "sampling.h" 00029 #include <stdarg.h> 00030 00031 using namespace lux; 00032 00033 void Blinn::Sample_f(const Vector &wo, Vector *wi, 00034 float u1, float u2, float *pdf) const { 00035 // Compute sampled half-angle vector $\wh$ for Blinn distribution 00036 float costheta = powf(u1, 1.f / (exponent+1.0f)); 00037 float sintheta = sqrtf(max(0.f, 1.f - costheta*costheta)); 00038 float phi = u2 * 2.f * M_PI; 00039 Vector H = SphericalDirection(sintheta, costheta, phi); 00040 if (!SameHemisphere(wo, H)) H.z *= -1.f; 00041 // Compute incident direction by reflecting about $\wh$ 00042 *wi = -wo + 2.f * Dot(wo, H) * H; 00043 // Compute PDF for \wi from Blinn distribution 00044 float blinn_pdf = ((exponent + 1.f) * 00045 powf(costheta, exponent)) / 00046 (2.f * M_PI * 4.f * Dot(wo, H)); 00047 00048 // NOTE - Ratow - Make sure pdf is non-negative 00049 if (blinn_pdf < 0.f) 00050 *pdf = 0.f; 00051 else 00052 *pdf = blinn_pdf; 00053 } 00054 float Blinn::Pdf(const Vector &wo, const Vector &wi) const { 00055 Vector H = Normalize(wo + wi); 00056 float costheta = fabsf(H.z); 00057 // Compute PDF for \wi from Blinn distribution 00058 float blinn_pdf = ((exponent + 1.f) * 00059 powf(costheta, exponent)) / 00060 (2.f * M_PI * 4.f * Dot(wo, H)); 00061 return blinn_pdf; 00062 }