问题
I am trying to use OpenGL to paint a view which is a subview of another view. I have created a view class for this purpose, and if I use this class in a simple test application it works fine. However, if I place an instance of this class on a particular page of my app, the OpenGL painting does not display anything. I am certain that the view is visible (I can set a background color, and that is displayed, and I can receive touch events). I can also trace through the OpenGL initialization and paint routines, and everything seems fine. My paint routine IS being called, and I call glGetError frequently and no errors are returned. I can compare tracing the routine with the case that works, and everything seems pretty much the same, but nothing paints (I even have simply tried doing nothing but clearing the window to black but that does nothing either).
The code for the app that does not work is far to complex to post here. I assume that I am doing something wrong, but for the life of me I cannot figure out what. Can anyone give me any ideas about why the OpenGL painting would appear to succeed and yet not draw anything, or suggest a strategy for figuring this out?
Thanks.
回答1:
The link between OpenGL and the outside world is platform specific and not part of the core API. So a problem there wouldn't affect the result of glGetError.
In the case of iOS the relevant call is EAGLContext -presentRenderbuffer:, which will work provided you've used renderbufferStorage:fromDrawable: to create storage for a render buffer from a CAEAGLLayer. You probably want to inspect the return result of presentRenderbuffer: and the code around that to look for an error rather than the internal GL state.
来源：https://stackoverflow.com/questions/7265594/opengl-ios-view-does-not-paint