Light Transport

#include "lantern.hpp"
#include <exception>
#include <iostream>
#include <numbers>

int main() {
    try {
        const auto integral=lantern::cosine_integral(65536,42);
        if (!integral) { std::cerr << integral.error().message << '\n'; return 1; }
        const std::vector<lantern::Sphere> spheres{{1,{0,0,0},1},{2,{3,0,0},0.5},{3,{-3,0,0},0.5}};
        const auto index=lantern::SceneIndex::build(spheres);
        if (!index) { std::cerr << index.error().message << '\n'; return 1; }
        const auto hit=index->closest({{0,0,4},{0,0,-1}});
        if (!hit || !*hit) { std::cerr << "Expected a central hit.\n"; return 1; }
        std::cout << "Uniform hemisphere estimate: " << *integral << " (analytic pi = " << std::numbers::pi
                  << ")\nBVH nodes: " << index->node_count() << "\nCentral hit id: " << (*hit)->id
                  << ", distance: " << (*hit)->distance << '\n';
        return 0;
    } catch (const std::exception&) { std::cerr << "CPU experiment could not complete.\n"; return 1; }
}