Question

I made a simple game for the iPhone using OpenGL ES. Everything works fine except for this problem:

I turn the phone completely off, then back on, then launch my app and I get this wierd flickering! Every other frame is correct… the incorrect frames are just the same frame over and over again. If I quit the app, launch it again everything is fine. If I quit and restart 10 times in a row everything is fine every time.

But if I turn the phone off, then back on, then launch the app I get the same flickering the first time I launch the app.

Why is this happening?!

Has anyone else had this problem?

Cheers!

Answer 1

Apple published additional information about this issue:

Q: My OpenGL ES application flickers.
Especially when running on iPhone 3GS,
the flickering seems to happen every
frame. How do I fix this problem?

A: By default, the contents of a
renderbuffer are invalidated after it
is presented to the screen (by calling
-EAGLContext/presentRenderbuffer:). Your application must completely
redraw the contents of the
renderbuffer every time you draw a
frame, otherwise you may observe
flickering or other unexpected
results.

You must provide a color to every
pixel on the screen. At the beginning
of your drawing code, it is a good
idea to use glClear() to initialize
the color buffer. A full-screen clear
of each of your color, depth, and
stencil buffers (if you’re using them)
at the start of a frame can also
generally improve your application’s
performance.

If your application needs to preserve
the drawable contents between frames,
you can add the option
kEAGLDrawablePropertyRetainedBacking =
YES to your CAEAGLLayer object’s
drawableProperties property. Using
this option requires additional memory
and can reduce your application’s
performance.