games101_Homework5

使用光线追踪来渲染图像，实现两个部分：光线的生成和光线与三角的求交

你需要修改的函数是：

• Renderer.cpp 中的 Render()：这里你需要为每个像素生成一条对应的光 线，然后调用函数 castRay() 来得到颜色，最后将颜色存储在帧缓冲区的相 应像素中。

• Triangle.hpp 中的 rayTriangleIntersect(): v0, v1, v2 是三角形的三个 顶点，orig 是光线的起点，dir 是光线单位化的方向向量。tnear, u, v 是你需 要使用我们课上推导的 Moller-Trumbore 算法来更新的参数。

Render()

void Renderer::Render(const Scene& scene)
{
    std::vector<Vector3f> framebuffer(scene.width * scene.height);      //需要填充的frame_buffer

    float scale = std::tan(deg2rad(scene.fov * 0.5f));      // t / |n|
    float imageAspectRatio = scene.width / (float)scene.height;     // r / t 

    // Use this variable as the eye position to start your rays.
    Vector3f eye_pos(0);    // 从(0, 0, 0)发出光线
    int m = 0;
    for (int j = 0; j < scene.height; ++j)
    {
        for (int i = 0; i < scene.width; ++i)   // 遍历每一个像素,像素点在n面上
        {
            // 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*

            // x对应于宽度,i = 0 对应 x = -r, i = width-1对应 x = r, 列方程解i和x的关系有：x = (2r / w-1) * i - r = [(2 / w-1) * i - 1] * r
            // y对应于高度,j = 0 对应 y = t, j = height-1对应 y = -t，列方程解j和y的关系有：y = (-2t / h-1) * j + t = [1 - (2 / h-1) * j] * t
            // n = -1则 |n| = 1， t = scale, r = t * asp = scale *imageAsp
            float x =  (2 / (float)(scene.width - 1) * i - 1) * scale * imageAspectRatio;
            float y =  (1 - 2 / (float)(scene.height - 1) * j) * scale;

            Vector3f dir = Vector3f(x, y, -1); // Don't forget to normalize this direction!
            framebuffer[m++] = castRay(eye_pos, normalize(dir), scene, 0);
        }
        UpdateProgress(j / (float)scene.height);
    }

    // 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] = (char)(255 * clamp(0, 1, framebuffer[i].x));
        color[1] = (char)(255 * clamp(0, 1, framebuffer[i].y));
        color[2] = (char)(255 * clamp(0, 1, framebuffer[i].z));
        fwrite(color, 1, 3, fp);
    }
    fclose(fp);
}

rayTriangleIntersect()

bool rayTriangleIntersect(const Vector3f& v0, const Vector3f& v1,
                          const Vector3f& v2, const Vector3f& orig,
                          const Vector3f& dir, float& tnear, float& u, float& v)
{
    // TODO: Implement this function that tests whether the triangle
    // that's specified bt v0, v1 and v2 intersects with the ray (whose origin is *orig* and direction is *dir*)
    // Also don't forget to update tnear, u and v.
    Vector3f E1 = v1 - v0;
    Vector3f E2 = v2 - v0;
    Vector3f S = orig - v0;
    Vector3f S1 = crossProduct(dir, E2);
    Vector3f S2 = crossProduct(S, E1);
    float det = dotProduct(E1, S1);
    if(det == 0 || det < 0) return false;

    float reS1E1 = 1. / det;
    float t = dotProduct(S2, E2) * reS1E1;
    float b1 = dotProduct(S1, S) * reS1E1;
    float b2 = dotProduct(S2, dir) *reS1E1;
    if(t >= 0 && b1 >= 0 && b2 >= 0 && 1 - b1 - b2 >= 0){
        tnear = t;
        u = b1;
        v = b2;
        return true;
    }
    return tnear > 0;
}

效果图