cloudy-raytracer/shader/brdfshader.cpp

#include <array>
#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;
    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);

        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(illum.direction, ray.normal)),
                                                    0,
                                                    std::acos(dotProduct(ray.direction, ray.normal)),
                                                    std::acos(dotProduct(D, L)));
    }
    // IMPLEMENT ME
    return illuminationColor;
}