/* This source is published under the following 3-clause BSD license. Copyright (c) 2012 - 2013, Lukas Hosek and Alexander Wilkie All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * None of the names of the contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* ============================================================================ This file is part of a sample implementation of the analytical skylight and solar radiance models presented in the SIGGRAPH 2012 paper "An Analytic Model for Full Spectral Sky-Dome Radiance" and the 2013 IEEE CG&A paper "Adding a Solar Radiance Function to the Hosek Skylight Model" both by Lukas Hosek and Alexander Wilkie Charles University in Prague, Czech Republic Version: 1.4a, February 22nd, 2013 Version history: 1.4a February 22nd, 2013 Removed unnecessary and counter-intuitive solar radius parameters from the interface of the colourspace sky dome initialisation functions. 1.4 February 11th, 2013 Fixed a bug which caused the relative brightness of the solar disc and the sky dome to be off by a factor of about 6. The sun was too bright: this affected both normal and alien sun scenarios. The coefficients of the solar radiance function were changed to fix this. 1.3 January 21st, 2013 (not released to the public) Added support for solar discs that are not exactly the same size as the terrestrial sun. Also added support for suns with a different emission spectrum ("Alien World" functionality). 1.2a December 18th, 2012 Fixed a mistake and some inaccuracies in the solar radiance function explanations found in ArHosekSkyModel.h. The actual source code is unchanged compared to version 1.2. 1.2 December 17th, 2012 Native RGB data and a solar radiance function that matches the turbidity conditions were added. 1.1 September 2012 The coefficients of the spectral model are now scaled so that the output is given in physical units: W / (m^-2 * sr * nm). Also, the output of the XYZ model is now no longer scaled to the range [0...1]. Instead, it is the result of a simple conversion from spectral data via the CIE 2 degree standard observer matching functions. Therefore, after multiplication with 683 lm / W, the Y channel now corresponds to luminance in lm. 1.0 May 11th, 2012 Initial release. Please visit http://cgg.mff.cuni.cz/projects/SkylightModelling/ to check if an updated version of this code has been published! ============================================================================ */ /* All instructions on how to use this code are in the accompanying header file. */ #include "sky_model.h" #include "sky_model_data.h" #include #include #include #include // Some macro definitions that occur elsewhere in ART, and that have to be // replicated to make this a stand-alone module. #ifndef MATH_PI # define MATH_PI 3.141592653589793 #endif #ifndef MATH_DEG_TO_RAD # define MATH_DEG_TO_RAD (MATH_PI / 180.0) #endif #ifndef DEGREES # define DEGREES *MATH_DEG_TO_RAD #endif #ifndef TERRESTRIAL_SOLAR_RADIUS # define TERRESTRIAL_SOLAR_RADIUS ((0.51 DEGREES) / 2.0) #endif #ifndef ALLOC # define ALLOC(_struct) ((_struct *)malloc(sizeof(_struct))) #endif // internal definitions typedef const double *ArHosekSkyModel_Dataset; typedef const double *ArHosekSkyModel_Radiance_Dataset; // internal functions static void ArHosekSkyModel_CookConfiguration(ArHosekSkyModel_Dataset dataset, SKY_ArHosekSkyModelConfiguration config, double turbidity, double albedo, double solar_elevation) { const double *elev_matrix; int int_turbidity = (int)turbidity; double turbidity_rem = turbidity - (double)int_turbidity; solar_elevation = pow(solar_elevation / (MATH_PI / 2.0), (1.0 / 3.0)); // alb 0 low turb elev_matrix = dataset + (9 * 6 * (int_turbidity - 1)); for (unsigned int i = 0; i < 9; ++i) { //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; config[i] = (1.0 - albedo) * (1.0 - turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[i] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[i + 9] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[i + 18] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[i + 27] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[i + 36] + pow(solar_elevation, 5.0) * elev_matrix[i + 45]); } // alb 1 low turb elev_matrix = dataset + (9 * 6 * 10 + 9 * 6 * (int_turbidity - 1)); for (unsigned int i = 0; i < 9; ++i) { //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; config[i] += (albedo) * (1.0 - turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[i] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[i + 9] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[i + 18] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[i + 27] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[i + 36] + pow(solar_elevation, 5.0) * elev_matrix[i + 45]); } if (int_turbidity == 10) return; // alb 0 high turb elev_matrix = dataset + (9 * 6 * (int_turbidity)); for (unsigned int i = 0; i < 9; ++i) { //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; config[i] += (1.0 - albedo) * (turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[i] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[i + 9] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[i + 18] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[i + 27] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[i + 36] + pow(solar_elevation, 5.0) * elev_matrix[i + 45]); } // alb 1 high turb elev_matrix = dataset + (9 * 6 * 10 + 9 * 6 * (int_turbidity)); for (unsigned int i = 0; i < 9; ++i) { //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; config[i] += (albedo) * (turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[i] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[i + 9] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[i + 18] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[i + 27] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[i + 36] + pow(solar_elevation, 5.0) * elev_matrix[i + 45]); } } static double ArHosekSkyModel_CookRadianceConfiguration(ArHosekSkyModel_Radiance_Dataset dataset, double turbidity, double albedo, double solar_elevation) { const double *elev_matrix; int int_turbidity = (int)turbidity; double turbidity_rem = turbidity - (double)int_turbidity; double res; solar_elevation = pow(solar_elevation / (MATH_PI / 2.0), (1.0 / 3.0)); // alb 0 low turb elev_matrix = dataset + (6 * (int_turbidity - 1)); //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; res = (1.0 - albedo) * (1.0 - turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[0] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[1] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[2] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[3] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[4] + pow(solar_elevation, 5.0) * elev_matrix[5]); // alb 1 low turb elev_matrix = dataset + (6 * 10 + 6 * (int_turbidity - 1)); //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; res += (albedo) * (1.0 - turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[0] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[1] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[2] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[3] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[4] + pow(solar_elevation, 5.0) * elev_matrix[5]); if (int_turbidity == 10) return res; // alb 0 high turb elev_matrix = dataset + (6 * (int_turbidity)); //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; res += (1.0 - albedo) * (turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[0] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[1] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[2] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[3] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[4] + pow(solar_elevation, 5.0) * elev_matrix[5]); // alb 1 high turb elev_matrix = dataset + (6 * 10 + 6 * (int_turbidity)); //(1-t).^3* A1 + 3*(1-t).^2.*t * A2 + 3*(1-t) .* t .^ 2 * A3 + t.^3 * A4; res += (albedo) * (turbidity_rem) * (pow(1.0 - solar_elevation, 5.0) * elev_matrix[0] + 5.0 * pow(1.0 - solar_elevation, 4.0) * solar_elevation * elev_matrix[1] + 10.0 * pow(1.0 - solar_elevation, 3.0) * pow(solar_elevation, 2.0) * elev_matrix[2] + 10.0 * pow(1.0 - solar_elevation, 2.0) * pow(solar_elevation, 3.0) * elev_matrix[3] + 5.0 * (1.0 - solar_elevation) * pow(solar_elevation, 4.0) * elev_matrix[4] + pow(solar_elevation, 5.0) * elev_matrix[5]); return res; } static double ArHosekSkyModel_GetRadianceInternal(SKY_ArHosekSkyModelConfiguration configuration, double theta, double gamma) { const double expM = exp(configuration[4] * gamma); const double rayM = cos(gamma) * cos(gamma); const double mieM = (1.0 + cos(gamma) * cos(gamma)) / pow((1.0 + configuration[8] * configuration[8] - 2.0 * configuration[8] * cos(gamma)), 1.5); const double zenith = sqrt(cos(theta)); return (1.0 + configuration[0] * exp(configuration[1] / (cos(theta) + 0.01))) * (configuration[2] + configuration[3] * expM + configuration[5] * rayM + configuration[6] * mieM + configuration[7] * zenith); } void SKY_arhosekskymodelstate_free(SKY_ArHosekSkyModelState *state) { free(state); } double SKY_arhosekskymodel_radiance(SKY_ArHosekSkyModelState *state, double theta, double gamma, double wavelength) { int low_wl = (int)((wavelength - 320.0) / 40.0); if (low_wl < 0 || low_wl >= 11) return 0.0; double interp = fmod((wavelength - 320.0) / 40.0, 1.0); double val_low = ArHosekSkyModel_GetRadianceInternal(state->configs[low_wl], theta, gamma) * state->radiances[low_wl] * state->emission_correction_factor_sky[low_wl]; if (interp < 1e-6) return val_low; double result = (1.0 - interp) * val_low; if (low_wl + 1 < 11) { result += interp * ArHosekSkyModel_GetRadianceInternal(state->configs[low_wl + 1], theta, gamma) * state->radiances[low_wl + 1] * state->emission_correction_factor_sky[low_wl + 1]; } return result; } // xyz and rgb versions SKY_ArHosekSkyModelState *SKY_arhosek_xyz_skymodelstate_alloc_init(const double turbidity, const double albedo, const double elevation) { SKY_ArHosekSkyModelState *state = ALLOC(SKY_ArHosekSkyModelState); state->solar_radius = TERRESTRIAL_SOLAR_RADIUS; state->turbidity = turbidity; state->albedo = albedo; state->elevation = elevation; for (unsigned int channel = 0; channel < 3; ++channel) { ArHosekSkyModel_CookConfiguration( datasetsXYZ[channel], state->configs[channel], turbidity, albedo, elevation); state->radiances[channel] = ArHosekSkyModel_CookRadianceConfiguration( datasetsXYZRad[channel], turbidity, albedo, elevation); } return state; }