tinyrenderer 相机移动

在 TinyRenderer 中，相机移动可以通过改变相机的位置来实现。具体来说，你需要在渲染循环中更新相机的位置，并将相机的位置传递给顶点着色器，以便在屏幕上正确地呈现场景。

以下是一些示例代码，可以帮助你开始实现相机移动：

首先，你需要定义一个相机类，用于跟踪相机的位置和方向：

class Camera {
public:
    Vector3f position;
    Vector3f forward;
    Vector3f up;

    Camera(const Vector3f& pos, const Vector3f& target, const Vector3f& up) {
        position = pos;
        forward = (target - pos).normalized();
        this->up = up.normalized();
    }

    Matrix4f get_view_matrix() const {
        Vector3f z = -forward;
        Vector3f x = up.cross(z).normalized();
        Vector3f y = z.cross(x).normalized();

        Matrix4f view;
        view << x.x(), x.y(), x.z(), -(x.dot(position)),
                y.x(), y.y(), y.z(), -(y.dot(position)),
                z.x(), z.y(), z.z(), -(z.dot(position)),
                0, 0, 0, 1;
        return view;
    }
};

然后，你需要在渲染循环中更新相机的位置，并将相机的位置传递给顶点着色器。在以下示例代码中，我们使用键盘控制相机的移动：

Camera camera(Vector3f(0, 0, 3), Vector3f(0, 0, 0), Vector3f(0, 1, 0));
float angle = 0;

while (!glfwWindowShouldClose(window)) {
    // 处理相机移动
    if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS) {
        camera.position += camera.forward * camera_speed;
    }
    if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS) {
        camera.position -= camera.forward * camera_speed;
    }
    if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS) {
        camera.position -= camera.forward.cross(camera.up).normalized() * camera_speed;
    }
    if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS) {
        camera.position += camera.forward.cross(camera.up).normalized() * camera_speed;
    }
    if (glfwGetKey(window, GLFW_KEY_Q) == GLFW_PRESS) {
        angle += camera_rotate_speed;
        camera.forward = Matrix3f::Identity() * AngleAxisf(angle, camera.up) * camera.forward;
    }
    if (glfwGetKey(window, GLFW_KEY_E) == GLFW_PRESS) {
        angle -= camera_rotate_speed;
        camera.forward = Matrix3f::Identity() * AngleAxisf(angle, camera.up) * camera.forward;
    }

    // 渲染场景
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glUniformMatrix4fv(model_loc, 1, GL_FALSE, model.data());
    glUniformMatrix4fv(view_loc, 1, GL_FALSE, camera.get_view_matrix().data());
    glUniformMatrix4fv(proj_loc, 1, GL_FALSE, proj.data());
    glBindVertexArray(vao);
    glDrawArrays(GL_TRIANGLES, 0, vb_size);

    glfwSwapBuffers(window);
    glfwPollEvents();
}

在顶点着色器中，你需要将相机的位置传递给着色器，并将模型视图投影矩阵中的相机变换修改为相机的位置：

#version 330 core

layout(location = 0) in vec3 position;

uniform mat4 model;
uniform mat4 view;
uniform mat4 proj;
uniform vec3 camera_pos;

void main() {
    gl_Position = proj * view * model * vec4(position, 1.0);
    // 计算相机空间中的位置
    vec3 camera_space_pos = (view * vec4(camera_pos, 1.0)).xyz;
    // 将相机空间中的位置传递给片段着色器
    gl_Position.z -= length(position - camera_space_pos) * 0.1;
}