cloudy-raytracer/shader/brdfshader.cpp

#include <array>
#include <cmath>
#include "light/light.h"
#include "scene/scene.h"
#include "shader/brdfshader.h"

BrdfShader::BrdfShader(char const *fileName, Color const &scale)
        : scale(scale), brdf(std::make_unique<BRDFRead>(fileName)) {}

Color BrdfShader::shade(Scene const &scene, Ray const &ray) const {
    Color illuminationColor;
    /*
     * Arvids Code
    static auto rebase = [](Vector3d const &axis_x,
                            Vector3d const &axis_y,
                            Vector3d const &axis_z,
                            Vector3d const &vec) {
        auto det = axis_x.x * axis_y.y * axis_z.z +
                   axis_x.y * axis_y.z * axis_z.x +
                   axis_x.z * axis_y.x * axis_z.y -
                   axis_x.x * axis_y.z * axis_z.y -
                   axis_x.y * axis_y.x * axis_z.z -
                   axis_x.z * axis_y.y * axis_z.x;
        // Calculate resulting vector by using inverse matrix of new base vectors
        return Vector3d{
                ((axis_y.y * axis_z.z - axis_y.z * axis_z.y) * vec.x +
                 (axis_y.z * axis_z.x - axis_y.x * axis_z.z) * vec.y +
                 (axis_y.x * axis_z.y - axis_z.x * axis_y.y) * vec.z) / det,
                ((axis_x.z * axis_z.y - axis_x.y * axis_z.z) * vec.x +
                 (axis_x.x * axis_z.z - axis_x.z * axis_z.x) * vec.y +
                 (axis_z.x * axis_x.y - axis_x.x * axis_z.y) * vec.z) / det,
                ((axis_x.y * axis_y.z - axis_x.z * axis_y.y) * vec.x +
                 (axis_y.x * axis_x.z - axis_x.x * axis_y.z) * vec.y +
                 (axis_x.x * axis_y.y - axis_y.x * axis_x.y) * vec.z) / det
        };
    };

    for (auto &light: scene.lights()) {

        auto illum = light->illuminate(scene, ray);
        if (dotProduct(ray.normal, illum.direction) <= EPSILON) {
            continue;
        }

        auto axis = orthoNormalized(ray.normal, ray.direction, illum.direction);
        auto axis_y = std::get<0>(axis);
        auto axis_x = std::get<1>(axis);
        auto axis_z = std::get<2>(axis);

        auto N = normalized(rebase(axis_x, axis_y, axis_z, ray.normal));
        auto D = normalized(rebase(axis_x, axis_y, axis_z, -ray.direction));
        auto L = normalized(rebase(axis_x, axis_y, axis_z, -illum.direction));
        D = axis_y * D.y + axis_z * D.z;
        L = axis_y * L.y + axis_z * L.z;

        illuminationColor += brdf->lookupBrdfValues(std::acos(dotProduct(ray.normal, -ray.direction)),
                                                    0.0f,
                                                    std::acos(dotProduct(illum.direction, ray.normal)),
                                                    std::acos(dotProduct(D, L)));
    }
    */
    // IMPLEMENT ME

    for(auto& light : scene.lights()){
        Light::Illumination illum = light->illuminate(scene, ray);

        Vector3d invertedDirection = -ray.direction;
        Vector3d invertedIllum = -illum.direction;

        // the dot-product cant be negative otherwise the light ray would come from the inside
        if(dotProduct(invertedIllum, ray.normal) < 0)
            continue;

        // Calculate coordinate System
        Vector3d axisX = crossProduct(invertedDirection, ray.normal);
        Vector3d axisY = crossProduct(axisX, ray.normal);

        // Project ray.direction and illum.direction into plane
        Vector2d projectedIllum = Vector2d(dotProduct(axisX, invertedIllum), dotProduct(axisY, invertedIllum));
        Vector2d projectedDirection = Vector2d(dotProduct(axisX, invertedDirection), dotProduct(axisY, invertedDirection));

        // get Z coordinate for theta angles
        double coordinateZDirection = dotProduct(ray.normal, invertedDirection);
        double coordinateZIllum = dotProduct(ray.normal, invertedIllum);

        // calculate theta1 and 2
        double theta1Correct = std::atan2(length(projectedDirection), coordinateZDirection);
        double theta2Correct = std::atan2(length(projectedIllum), coordinateZIllum);

        // calculate phi
        double phi = std::atan2(projectedIllum.u, projectedIllum.v);

        illuminationColor += brdf->lookupBrdfValues(theta1Correct, 0.0, theta2Correct, phi);

    }
    return illuminationColor;
}