GAMES101 作业1

请用来检验答案是否正确

思路

根据Games101第四讲的内容来写即可，核心的部分还是M(p) = M(o) * M(p->o)，具体的推动过程课程内讲的很详细，点赞~
这里有一点需要注意的是，get_projection_matrix传入的参数是“距离值”，因此是正的，但计算过程中需要考虑方向，而在右手坐标系下我们推导过程默认相机看向方向是-Z，因此这里需要对传入值进行取负操作。

Code

#include "Triangle.hpp"
#include "rasterizer.hpp"
#include <eigen3/Eigen/Eigen>
#include <iostream>
#include <opencv2/opencv.hpp>

constexpr double MY_PI = 3.1415926;

Eigen::Matrix4f get_view_matrix(Eigen::Vector3f eye_pos)
{
    Eigen::Matrix4f view = Eigen::Matrix4f::Identity();

    Eigen::Matrix4f translate;
    translate << 1, 0, 0, -eye_pos[0], 0, 1, 0, -eye_pos[1], 0, 0, 1,
        -eye_pos[2], 0, 0, 0, 1;

    view = translate * view;

    return view;
}

Eigen::Matrix4f get_model_matrix(float rotation_angle)
{
    Eigen::Matrix4f model = Eigen::Matrix4f::Identity();

    // TODO: Implement this function
    // Create the model matrix for rotating the triangle around the Z axis.
    // Then return it.
    float a = rotation_angle * MY_PI / 180;
    model << cos(a), -sin(a), 0, 0,
        sin(a), cos(a), 0, 0,
        0, 0, 1, 0,
        0, 0, 0, 1;
    return model;
}

Eigen::Matrix4f get_projection_matrix(float eye_fov, float aspect_ratio,
                                      float zNear, float zFar)
{
    // Students will implement this function

    Eigen::Matrix4f projection = Eigen::Matrix4f::Identity();

    // TODO: Implement this function
    // Create the projection matrix for the given parameters.
    // Then return it.

    float fov = eye_fov * MY_PI / 180;
    // 右手坐标系 看向方向z为负
    float n = -zNear;
    float f = -zFar;
    float t = tan(0.5 * fov) * abs(n);
    float r = aspect_ratio * t;
    float l = -r;
    float b = -t;

    // 正交投影-平移
    Eigen::Matrix4f orthT = Eigen::Matrix4f::Identity();
    orthT << 1, 0, 0, -(r + l) / 2,
        0, 1, 0, -(t + b) / 2,
        0, 0, 1, -(n + f) / 2,
        0, 0, 0, 1;

    // 正交投影-缩放
    Eigen::Matrix4f orthS = Eigen::Matrix4f::Identity();
    orthS << 2 / (r - l), 0, 0, 0,
        0, 2 / (t - b), 0, 0,
        0, 0, 2 / (n - f), 0,
        0, 0, 0, 1;

    // 透视模型 挤压到 正交模型
    Eigen::Matrix4f p2o = Eigen::Matrix4f::Identity();
    p2o << n, 0, 0, 0,
        0, n, 0, 0,
        0, 0, n + f, -n * f,
        0, 0, 1, 0;

    // Mo * Mp2o 最后得到Mp
    projection = orthS * orthT * p2o;
    return projection;
}

int main(int argc, const char **argv)
{
    float angle = 0;
    bool command_line = false;
    std::string filename = "output.png";

    if (argc >= 3)
    {
        command_line = true;
        angle = std::stof(argv[2]); // -r by default
        if (argc == 4)
        {
            filename = std::string(argv[3]);
        }
        else
            return 0;
    }

    rst::rasterizer r(700, 700);

    Eigen::Vector3f eye_pos = {0, 0, 5};

    std::vector<Eigen::Vector3f> pos{{2, 0, -2}, {0, 2, -2}, {-2, 0, -2}};

    std::vector<Eigen::Vector3i> ind{{0, 1, 2}};

    auto pos_id = r.load_positions(pos);
    auto ind_id = r.load_indices(ind);

    int key = 0;
    int frame_count = 0;

    if (command_line)
    {
        r.clear(rst::Buffers::Color | rst::Buffers::Depth);

        r.set_model(get_model_matrix(angle));
        r.set_view(get_view_matrix(eye_pos));
        r.set_projection(get_projection_matrix(45, 1, 0.1, 50));

        r.draw(pos_id, ind_id, rst::Primitive::Triangle);
        cv::Mat image(700, 700, CV_32FC3, r.frame_buffer().data());
        image.convertTo(image, CV_8UC3, 1.0f);

        cv::imwrite(filename, image);

        return 0;
    }

    while (key != 27)
    {
        r.clear(rst::Buffers::Color | rst::Buffers::Depth);

        r.set_model(get_model_matrix(angle));
        r.set_view(get_view_matrix(eye_pos));
        r.set_projection(get_projection_matrix(45, 1, 0.1, 50));

        r.draw(pos_id, ind_id, rst::Primitive::Triangle);

        cv::Mat image(700, 700, CV_32FC3, r.frame_buffer().data());
        image.convertTo(image, CV_8UC3, 1.0f);
        cv::imshow("image", image);
        key = cv::waitKey(10);

        std::cout << "frame count: " << frame_count++ << '
';

        if (key == 'a')
        {
            angle += 10;
        }
        else if (key == 'd')
        {
            angle -= 10;
        }
    }

    return 0;
}