Why use CADisplayLink?

[tclh123]

In your C++ sample, called [myGLView startAnimation];, which I think is no need.
Render will be called in camera caputre loop. And CADisplayLink only will call selector when the display needs to refresh, and in your sample it rarely happens(I don't know why).

Thanks in advance.

[sonsongithub]

It's a legacy code.