intersections.hpp

inline bool intersect_ray_aabb(const glm::vec3 &origin, const glm::vec3 &dir, const AABB &aabb) {
    float tmin, tmax, tymin, tymax, tzmin, tzmax;

    glm::vec3 bounds[2];
    bounds[0] = aabb.min();
    bounds[1] = aabb.max();

    glm::vec3 invdir = 1.f / dir;
    glm::i8vec3 sign;

    sign.x = (invdir.x < 0);
    sign.y = (invdir.y < 0);
    sign.z = (invdir.z < 0);

    tmin = (bounds[sign.x].x - origin.x) * invdir.x;
    tmax = (bounds[1 - sign.x].x - origin.x) * invdir.x;
    tymin = (bounds[sign.y].y - origin.y) * invdir.y;
    tymax = (bounds[1 - sign.y].y - origin.y) * invdir.y;

    if ((tmin > tymax) || (tymin > tmax))
        return false;
    if (tymin > tmin)
        tmin = tymin;
    if (tymax < tmax)
        tmax = tymax;

    tzmin = (bounds[sign.z].z - origin.z) * invdir.z;
    tzmax = (bounds[1 - sign.z].z - origin.z) * invdir.z;

    if ((tmin > tzmax) || (tzmin > tmax))
        return false;
    if (tzmin > tmin)
        tmin = tzmin;
    if (tzmax < tmax)
        tmax = tzmax;

    return true;
}