Vector3f Scene::castRay(const Ray &ray, int depth) const
{
    // TO DO Implement Path Tracing Algorithm here

    
    Vector3f result(0.0f);
    
    Intersection wo_inter = intersect(ray);
    if (!wo_inter.happened)
    {
        return result;
    }
    // 有光源直接用
    if (wo_inter.m->hasEmission())
    {
        return wo_inter.m->getEmission();
    }
    

    Intersection ws_inter;
    float pdf;
    sampleLight(ws_inter, pdf);

    Vector3f p = wo_inter.coords;
    Vector3f x = ws_inter.coords;
    Vector3f wo = ray.direction;
    Vector3f ws = (x - p).normalized();
    Vector3f N = wo_inter.normal.normalized();
    Vector3f NN = ws_inter.normal.normalized();
    Vector3f emit = ws_inter.emit;

    float ws_distance = (x - p).norm();

    Ray incoming(p, ws);

    Intersection in_intersection = intersect(incoming);
    
    Vector3f l_dir;

    if(in_intersection.distance - ws_distance >= -EPSILON){
        l_dir = emit * wo_inter.m->eval(wo, ws, N)
            * dotProduct(ws, N) * dotProduct(-ws, NN)
            / (ws_distance * ws_distance)
            / pdf;
        // std::cout << l_dir << std::endl;
    } 
    
    // if(get_random_float() > RussianRoulette) {
    //     return l_dir;
    // }

    Vector3f l_indir;

    // Vector3f wi_dir = wo_inter.m->sample(wo, N).normalized();
    // Ray wi_ray(wo_inter.coords, wi_dir);
    // Intersection wi_inter = intersect(wi_ray);
    // if (wi_inter.happened && (!wi_inter.m->hasEmission())) {
    //     l_indir = castRay(wi_ray, depth + 1) * wo_inter.m->eval(ray.direction, wi_ray.direction, N)
    //         * dotProduct(wi_ray.direction, N)
    //         / wo_inter.m->pdf(ray.direction, wi_ray.direction, N)
    //         / RussianRoulette;
    // }
    return l_dir + l_indir;
}

只做了直接光照，光源是直接投到了观察方向才有展示，看了比较久没发现什么原因。。