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 // orennayar.cpp* 00024 #include "orennayar.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 SWCSpectrum OrenNayar::f(const Vector &wo, 00034 const Vector &wi) const { 00035 float sinthetai = SinTheta(wi); 00036 float sinthetao = SinTheta(wo); 00037 // Compute cosine term of Oren--Nayar model 00038 float maxcos = 0.f; 00039 if (sinthetai > 1e-4 && sinthetao > 1e-4) { 00040 float sinphii = SinPhi(wi), cosphii = CosPhi(wi); 00041 float sinphio = SinPhi(wo), cosphio = CosPhi(wo); 00042 float dcos = cosphii * cosphio + sinphii * sinphio; 00043 maxcos = max(0.f, dcos); 00044 } 00045 // Compute sine and tangent terms of Oren--Nayar model 00046 float sinalpha, tanbeta; 00047 if (fabsf(CosTheta(wi)) > fabsf(CosTheta(wo))) { 00048 sinalpha = sinthetao; 00049 tanbeta = sinthetai / fabsf(CosTheta(wi)); 00050 } 00051 else { 00052 sinalpha = sinthetai; 00053 tanbeta = sinthetao / fabsf(CosTheta(wo)); 00054 } 00055 return R * INV_PI * 00056 (A + B * maxcos * sinalpha * tanbeta); 00057 } 00058