src/Math/Ray.hpp


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#pragma once

#include "../Common/Lambda.hpp"
#include "AABB.hpp"
#include "Vector.hpp"

struct Ray {
    struct RaycastResult {
        Bool hit = false;
        Vec3 point;
        Vec3 normal;
    };

    // https://gdbooks.gitbooks.io/3dcollisions/content/Chapter3/raycast_aabb.html
    RaycastResult cast(AABB box) const {
        Vec3 t_from = (box.min - origin) / direction;
        Vec3 t_to = (box.max - origin) / direction;

        Real t_min = t_from.zip(t_to, LAMBDA(std::min, 2)).reduce(LAMBDA(std::max, 2));
        Real t_max = t_from.zip(t_to, LAMBDA(std::max, 2)).reduce(LAMBDA(std::min, 2));

        if (t_max < 0 || t_min > t_max) return {};

        return {
            .hit = true,
            .point = origin + direction * t_min,
            .normal = t_from.zip(t_to, [](auto a, auto b) { return a < b ? -1.0 : 1.0; })
        };
    }

    Vec3 origin;
    Vec3 direction;
};