medium.cpp

/*
    pbrt source code is Copyright(c) 1998-2016
                        Matt Pharr, Greg Humphreys, and Wenzel Jakob.

    This file is part of pbrt.

    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.

    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
    HOLDER OR CONTRIBUTORS 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.

 */


// core/medium.cpp*
#include "medium.h"
#include "memory.h"
#include "sampler.h"
#include "stats.h"
#include "interaction.h"

namespace pbrt {

// Media Local Definitions
struct MeasuredSS {
    const char *name;
    Float sigma_prime_s[3], sigma_a[3];  // mm^-1
};

static MeasuredSS SubsurfaceParameterTable[] = {
    // From "A Practical Model for Subsurface Light Transport"
    // Jensen, Marschner, Levoy, Hanrahan
    // Proc SIGGRAPH 2001
    {
        "Apple", {2.29, 2.39, 1.97}, {0.0030, 0.0034, 0.046},
    },
    {
        "Chicken1", {0.15, 0.21, 0.38}, {0.015, 0.077, 0.19},
    },
    {
        "Chicken2", {0.19, 0.25, 0.32}, {0.018, 0.088, 0.20},
    },
    {
        "Cream", {7.38, 5.47, 3.15}, {0.0002, 0.0028, 0.0163},
    },
    {
        "Ketchup", {0.18, 0.07, 0.03}, {0.061, 0.97, 1.45},
    },
    {
        "Marble", {2.19, 2.62, 3.00}, {0.0021, 0.0041, 0.0071},
    },
    {
        "Potato", {0.68, 0.70, 0.55}, {0.0024, 0.0090, 0.12},
    },
    {
        "Skimmilk", {0.70, 1.22, 1.90}, {0.0014, 0.0025, 0.0142},
    },
    {
        "Skin1", {0.74, 0.88, 1.01}, {0.032, 0.17, 0.48},
    },
    {
        "Skin2", {1.09, 1.59, 1.79}, {0.013, 0.070, 0.145},
    },
    {
        "Spectralon", {11.6, 20.4, 14.9}, {0.00, 0.00, 0.00},
    },
    {
        "Wholemilk", {2.55, 3.21, 3.77}, {0.0011, 0.0024, 0.014},
    },

    // From "Acquiring Scattering Properties of Participating Media by
    // Dilution",
    // Narasimhan, Gupta, Donner, Ramamoorthi, Nayar, Jensen
    // Proc SIGGRAPH 2006
    {"Lowfat Milk", {0.89187, 1.5136, 2.532}, {0.002875, 0.00575, 0.0115}},
    {"Reduced Milk",
     {2.4858, 3.1669, 4.5214},
     {0.0025556, 0.0051111, 0.012778}},
    {"Regular Milk", {4.5513, 5.8294, 7.136}, {0.0015333, 0.0046, 0.019933}},
    {"Espresso", {0.72378, 0.84557, 1.0247}, {4.7984, 6.5751, 8.8493}},
    {"Mint Mocha Coffee", {0.31602, 0.38538, 0.48131}, {3.772, 5.8228, 7.82}},
    {"Lowfat Soy Milk",
     {0.30576, 0.34233, 0.61664},
     {0.0014375, 0.0071875, 0.035937}},
    {"Regular Soy Milk",
     {0.59223, 0.73866, 1.4693},
     {0.0019167, 0.0095833, 0.065167}},
    {"Lowfat Chocolate Milk",
     {0.64925, 0.83916, 1.1057},
     {0.0115, 0.0368, 0.1564}},
    {"Regular Chocolate Milk",
     {1.4585, 2.1289, 2.9527},
     {0.010063, 0.043125, 0.14375}},
    {"Coke", {8.9053e-05, 8.372e-05, 0}, {0.10014, 0.16503, 0.2468}},
    {"Pepsi", {6.1697e-05, 4.2564e-05, 0}, {0.091641, 0.14158, 0.20729}},
    {"Sprite",
     {6.0306e-06, 6.4139e-06, 6.5504e-06},
     {0.001886, 0.0018308, 0.0020025}},
    {"Gatorade",
     {0.0024574, 0.003007, 0.0037325},
     {0.024794, 0.019289, 0.008878}},
    {"Chardonnay",
     {1.7982e-05, 1.3758e-05, 1.2023e-05},
     {0.010782, 0.011855, 0.023997}},
    {"White Zinfandel",
     {1.7501e-05, 1.9069e-05, 1.288e-05},
     {0.012072, 0.016184, 0.019843}},
    {"Merlot", {2.1129e-05, 0, 0}, {0.11632, 0.25191, 0.29434}},
    {"Budweiser Beer",
     {2.4356e-05, 2.4079e-05, 1.0564e-05},
     {0.011492, 0.024911, 0.057786}},
    {"Coors Light Beer",
     {5.0922e-05, 4.301e-05, 0},
     {0.006164, 0.013984, 0.034983}},
    {"Clorox",
     {0.0024035, 0.0031373, 0.003991},
     {0.0033542, 0.014892, 0.026297}},
    {"Apple Juice",
     {0.00013612, 0.00015836, 0.000227},
     {0.012957, 0.023741, 0.052184}},
    {"Cranberry Juice",
     {0.00010402, 0.00011646, 7.8139e-05},
     {0.039437, 0.094223, 0.12426}},
    {"Grape Juice", {5.382e-05, 0, 0}, {0.10404, 0.23958, 0.29325}},
    {"Ruby Grapefruit Juice",
     {0.011002, 0.010927, 0.011036},
     {0.085867, 0.18314, 0.25262}},
    {"White Grapefruit Juice",
     {0.22826, 0.23998, 0.32748},
     {0.0138, 0.018831, 0.056781}},
    {"Shampoo",
     {0.0007176, 0.0008303, 0.0009016},
     {0.014107, 0.045693, 0.061717}},
    {"Strawberry Shampoo",
     {0.00015671, 0.00015947, 1.518e-05},
     {0.01449, 0.05796, 0.075823}},
    {"Head & Shoulders Shampoo",
     {0.023805, 0.028804, 0.034306},
     {0.084621, 0.15688, 0.20365}},
    {"Lemon Tea Powder",
     {0.040224, 0.045264, 0.051081},
     {2.4288, 4.5757, 7.2127}},
    {"Orange Powder",
     {0.00015617, 0.00017482, 0.0001762},
     {0.001449, 0.003441, 0.007863}},
    {"Pink Lemonade Powder",
     {0.00012103, 0.00013073, 0.00012528},
     {0.001165, 0.002366, 0.003195}},
    {"Cappuccino Powder", {1.8436, 2.5851, 2.1662}, {35.844, 49.547, 61.084}},
    {"Salt Powder", {0.027333, 0.032451, 0.031979}, {0.28415, 0.3257, 0.34148}},
    {"Sugar Powder",
     {0.00022272, 0.00025513, 0.000271},
     {0.012638, 0.031051, 0.050124}},
    {"Suisse Mocha Powder", {2.7979, 3.5452, 4.3365}, {17.502, 27.004, 35.433}},
    {"Pacific Ocean Surface Water",
     {0.0001764, 0.00032095, 0.00019617},
     {0.031845, 0.031324, 0.030147}}};

// Media Definitions
PhaseFunction::~PhaseFunction() { }

bool GetMediumScatteringProperties(const std::string &name, Spectrum *sigma_a,
                                   Spectrum *sigma_prime_s) {
    for (MeasuredSS &mss : SubsurfaceParameterTable) {
        if (name == mss.name) {
            *sigma_a = Spectrum::FromRGB(mss.sigma_a);
            *sigma_prime_s = Spectrum::FromRGB(mss.sigma_prime_s);
            return true;
        }
    }
    return false;
}

// HenyeyGreenstein Method Definitions
Float HenyeyGreenstein::Sample_p(const Vector3f &wo, Vector3f *wi,
                                 const Point2f &u) const {
    ProfilePhase _(Prof::PhaseFuncSampling);
    // Compute $\cos \theta$ for Henyey--Greenstein sample
    Float cosTheta;
    if (std::abs(g) < 1e-3)
        cosTheta = 1 - 2 * u[0];
    else {
        Float sqrTerm = (1 - g * g) / (1 + g - 2 * g * u[0]);
        cosTheta = -(1 + g * g - sqrTerm * sqrTerm) / (2 * g);
    }

    // Compute direction _wi_ for Henyey--Greenstein sample
    Float sinTheta = std::sqrt(std::max((Float)0, 1 - cosTheta * cosTheta));
    Float phi = 2 * Pi * u[1];
    Vector3f v1, v2;
    CoordinateSystem(wo, &v1, &v2);
    *wi = SphericalDirection(sinTheta, cosTheta, phi, v1, v2, wo);
    return PhaseHG(cosTheta, g);
}

Float HenyeyGreenstein::p(const Vector3f &wo, const Vector3f &wi) const {
    ProfilePhase _(Prof::PhaseFuncEvaluation);
    return PhaseHG(Dot(wo, wi), g);
}

}  // namespace pbrt