【Games101 作业6 + 附加题】渲染兔子 BVH SAH 代码

基础题部分

根据教程PDF，首先需要引用如下函数（在作业5的基础上稍作修改）：

renderer() in Renderer.cpp

解说见注释：

// The main render function. This where we iterate over all pixels in the image,
// generate primary rays and cast these rays into the scene. The content of the
// framebuffer is saved to a file.
void Renderer::Render(const Scene& scene)
{
    std::vector<Vector3f> framebuffer(scene.width * scene.height);

    float scale = tan(deg2rad(scene.fov * 0.5));
    float imageAspectRatio = scene.width / (float)scene.height;
    Vector3f eye_pos(-1, 5, 10);
    int m = 0;
    for (uint32_t j = 0; j < scene.height; ++j) {
        for (uint32_t i = 0; i < scene.width; ++i) {
            // generate primary ray direction
            // TODO: Find the x and y positions of the current pixel to get the
            // direction
            //  vector that passes through it.
            // Also, don't forget to multiply both of them with the variable
            // *scale*, and x (horizontal) variable with the *imageAspectRatio*
            float x = (2 * (i + 0.5) / (float)scene.width - 1) * imageAspectRatio * scale;
            float y = (1 - 2 * (j + 0.5) / (float)scene.height) * scale;
            
            // 从这里开始
            Vector3f dir = normalize(Vector3f(x, y, -1)); // Don't forget to normalize this direction!

            // 在本次代码框架中，castRay()函数放在了Scene类中
            // 并且castRay()的传入参数修改为(const Ray &ray, int depth)
            // 所以要先声明Ray ray(const Vector3f& ori, const Vector3f& dir)
            Ray ray(eye_pos, dir);
            
            // 调用scene.castRay()
            // 并将返回结果(Vector3f类型的像素RGB颜色)存入framebuffer中
            framebuffer[m++] = scene.castRay(ray, 0);
        }
        UpdateProgress(j / (float)scene.height);
    }
    UpdateProgress(1.f);

    // save framebuffer to file
    FILE* fp = fopen("binary.ppm", "wb");
    (void)fprintf(fp, "P6\n%d %d\n255\n", scene.width, scene.height);
    for (auto i = 0; i < scene.height * scene.width; ++i) {
        static unsigned char color[3];
        color[0] = (unsigned char)(255 * clamp(0, 1, framebuffer[i].x));
        color[1] = (unsigned char)(255 * clamp(0, 1, framebuffer[i].y));
        color[2] = (unsigned char)(255 * clamp(0, 1, framebuffer[i].z));
        fwrite(color, 1, 3, fp);
    }
    fclose(fp);    
}

Triangle::getIntersection in Triangle.hpp

解说见注释：

// TODO find ray triangle intersection
inline Intersection Triangle::getIntersection(Ray ray)
{
    Intersection inter;

    if (dotProduct(ray.direction, normal) > 0)
        return inter;
    
    // u,v为三角形重心坐标，即PPT中的b1,b2
    // t_tmp是PPT中的t
    double u, v, t_tmp = 0;
    Vector3f pvec = crossProduct(ray.direction, e2);
    double det = dotProduct(e1, pvec);
    if (fabs(det) < EPSILON)
        return inter;

    double det_inv = 1. / det;
    Vector3f tvec = ray.origin - v0;
    u = dotProduct(tvec, pvec) * det_inv;
    if (u < 0 || u > 1)
        return inter;
    Vector3f qvec = crossProduct(tvec, e1);
    v = dotProduct(ray.direction, qvec) * det_inv;