1.8.1 Exercises

1

Try experimenting with the FoV and aspect-ratio parameters of GLM's projection function. See if you can figure out how those affect the perspective frustum.

2

Play with the view matrix by translating in several directions and see how the scene changes. Think of the view matrix as a camera object.

3

Try to make every 3rd container (including the 1st) rotate over time, while leaving the other containers static using just the model matrix

1

WebGL Example
用上面网站进行测试

FoV

aspect: 1.0 (width/height)
near: 1.0
far: 10.0

Fov = 5

|400x265

Fov = 45

|399x263

Fov = 90

|401x266

Fov = 135

|402x267

Fov = 179

|398x264

Fov从5增加到179的过程中视野逐渐增大，物体越来越小，离镜头（观察点/camera）越来越远。

aspect-ratio

aspect = 0.1

|400x264

aspect = 1.0

|401x268

aspect = 2.0

|401x266

aspect = 5.0

|399x263

aspect 从0.1 增加到5.0的过程中，高度保持不变，宽度逐渐增加。积木离镜头的距离保持不变，但是积木的形状由拉伸变换为压缩

2

把view matrix 视作camera object，调整camera 的位置，观察不同位置下呈现的图像效果。
实现：

        glm::mat4 view = glm::mat4(1.0f);
        view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
        view = glm::rotate(view, glm::radians(-45.0f), glm::vec3(0.0f, 1.0f, 0.0f));

把camera 绕y轴 向右（顺时针-正）转动45°，相当于把world space 向左（逆时针-负）转动45°
效果：

camera右转动45°

|399x318

右60°

|400x319

右75°

|398x317

3

只让序号为3的倍数的cube 旋转，其余保持静止

参考

    glm::mat4 model = glm::mat4(1.0f);
    model = glm::translate(model, cubePositions[i]);
    float angle = 20.0f * i; 
    if(i % 3 == 0)  // every 3rd iteration (including the first) we set the angle using GLFW's time function.
        angle = glfwGetTime() * 25.0f;
    model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));

我的

          glm::mat4 model = glm::mat4(1.0f);
            model = glm::translate(model, cubePositions[i]);
            if(i % 3 == 0)
            {
                float angle = 20.0f * i;
                model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
            }

效果：

第一个container 没有旋转是因为i 为0-》转动的角度为0°