3D基础知识

文章来源：

http://www.codeproject.com/Articles/42086/Space-and-Matrix-Transformations-Building-a-3D-Eng

 

小结：

projection transform 投影变换
diagonal 对角线
quaternion 四元数
transpose matrix 转置矩阵
identity matrix 单位矩阵
Local transform 局部转换
cross product 叉积，向量积
dot product 点积，标量积，数量积
perspective transform 透视变换

OpenGL 使用的是右手坐标系统。

The World Space Transform is the first transform usually applied to a model.
This transform is normally used to scale and orient the model relative to its world.
The Model is defined in a model space coordinate system and needs to be translated
to the world coordinate system.
通常，模型面对的第一个变换就是世界空间变换，这种变换通常用来对模型进行缩放以适应模型展现，
被定义在模型坐标系统中的模型需要将其转变成世界坐标系。

After a model is transformed to its position into World Space it will then be
transformed in to View Space or Camera Space.
模型被转变成世界坐标系以后，接着才能被转变成视口空间或摄像机空间

Perspective Transform[透视变换]
After a model is transformed to its position into View Space, it will then be transformed
in to its final viewed position via projection transformation. There are two basic types
of projection transforms that I am aware of: Orthographic, and Perspective. The Perspective
projection mimics the way we perceive the real world. Objects that are closer appear larger
and parallel lines converage at the horizon. Here is how the Perspective transform is constructed.
当一个模型被变换到视口空间之后，然后需要通过透视变换来获取最终的视图位置，这里有两种基本的投影变换:
正交投影 和 透视投影，透视投影模拟我们所感知的真实世界，对象更接近说看到的，