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Eigen::Matrix4f get_model_matrix(float rotation_angle)
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{
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    Eigen::Matrix4f model = Eigen::Matrix4f::Identity();
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    // TODO: Implement this function
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    // Create the model matrix for rotating the triangle around the Z axis.
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    // Then return it.
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  float angle = rotation_angle / 180.0 * MY_PI;
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    model(0, 0) = std::cos(angle);
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  model(0, 1) = -std::sin(angle);
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  model(1, 0) = std::sin(angle);
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    model(1, 1) = std::cos(angle);
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    return model;
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}

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Eigen::Matrix4f get_projection_matrix(float eye_fov, float aspect_ratio,
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                                      float zNear, float zFar)
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{
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    // Students will implement this function
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    Eigen::Matrix4f projection = Eigen::Matrix4f::Identity();
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    // TODO: Implement this function
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    // Create the projection matrix for the given parameters.
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    // Then return it.
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    Eigen::Matrix4f prespToortho = Eigen::Matrix4f::Identity();
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    Eigen::Matrix4f ortho = Eigen::Matrix4f::Identity();
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    Eigen::Matrix4f translate = Eigen::Matrix4f::Identity();
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    Eigen::Matrix4f scale = Eigen::Matrix4f::Identity();
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  float t = std::tan(eye_fov / 180.0 * MY_PI / 2) * zNear;
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    float b = -t;
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    float r = t * aspect_ratio;
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  float l = -r;
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  translate(0, 3) = -(r + l) / 2;
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    translate(1, 3) = -(t + b) / 2;
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    translate(2, 3) = -(zNear + zFar) / 2;
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  scale(0, 0) = 2 / (r - l);
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  scale(1, 1) = 2 / (t - b);
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  scale(2, 2) = 2 / (zNear - zFar);
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  ortho = scale * translate;
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  prespToortho(0, 0) = zNear;
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    prespToortho(1, 1) = zNear;
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  prespToortho(2, 2) = zNear + zFar;
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  prespToortho(2, 3) = -zNear * zFar;
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    prespToortho(3, 2) = 1;
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    prespToortho(3, 3) = 0;
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  projection = ortho * prespToortho;
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    return projection;
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}

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Eigen::Matrix4f get_rotation(Eigen::Vector3f axis, float angle) {
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    // 最终要返回的 4x4 齐次矩阵，先初始化为单位矩阵
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    Eigen::Matrix4f rotation = Eigen::Matrix4f::Identity();
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    // 1. 角度转弧度 (假设输入的 angle 是角度)
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    // 注意：如果你的环境中没有 MY_PI，可以使用 std::acos(-1.0f) 代替
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    float rad = angle / 180.0f * MY_PI;
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    // 2. 将旋转轴标准化为单位向量 (非常重要！公式的前提是单位向量)
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    Eigen::Vector3f n = axis.normalized();
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    // 3. 构建 3x3 单位矩阵 I
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    Eigen::Matrix3f I = Eigen::Matrix3f::Identity();
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    // 4. 构建叉积矩阵 (反对称矩阵) N
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    Eigen::Matrix3f N;
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    N << 0, -n.z(), n.y(),
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        n.z(), 0, -n.x(),
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        -n.y(), n.x(), 0;
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    // 5. 应用罗德里格斯公式计算 3x3 旋转矩阵 R
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    // n * n.transpose() 就是向量的外积 n * n^T
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    Eigen::Matrix3f R = std::cos(rad) * I +
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        (1.0f - std::cos(rad)) * n * n.transpose() +
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        std::sin(rad) * N;
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    // 6. 将 3x3 的旋转矩阵填入 4x4 矩阵的左上角
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    // Eigen 提供了便捷的方法 topLeftCorner 或者 block
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    rotation.topLeftCorner<3, 3>() = R;
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    return rotation;
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}