【Camera】
1、Camera属性如下
属性说明参考：file:///D:/Program%20Files%20(x86)/Unity/Editor/Data/Documentation/Documentation/Components/class-Camera.html
2、Clear FLags可以选择Depth Only选项。
If you wanted to draw a player's gun without letting it get clipped inside the environment, you would set one Camera at Depth 0 to draw the environment, and another Camera at Depth 1 to draw the weapon alone. The weapon Camera's Clear Flags should be set to to depth only. This will keep the graphical display of the environment on the screen, but discard all information about where each object exists in 3-D space. When the gun is drawn, the opaque parts will completely cover anything drawn, regardless of how close the gun is to the wall.
Camera每帧会绘制图像，燕绘制图像前会清空color buffer、depth buffer。Depth only的意思就是只清除Depth Buffer。
3、把Camera挂于一个GameObject层级下，则Camera会随着此GameObject运行，即可实现跟随效果。
4、Cameras can be used in physics simulation if you add a Rigidbody Component.
5、Cameras cannot render to the Game Screen and a Render Texture at the same time, only one or the other.
6、Unity comes with pre-installed Camera scripts, found in
