From: Rich Cook (
Date: Tue Dec 15 2009 - 15:03:07 CST

I'm wondering if folks here can help me troubleshoot this issue.

We have VMD installed on our large computer clusters and users like to
visualize their data and display back to their desktops. This is more
convenient than moving the data.

A few of my users are having flickering issues with VMD on their Mac
laptops. The symptoms: VMD runs normally, but the screen flickers
between a garbage image, mostly white, and the correct display. This
makes VMD unusable for them in the way they'd like to be using it.

They are running Mac OS X 10.5.8, using Apple's X11 ( version
2.1.6 or the newer XQuartz 2.4.0 from
  and using ATI graphics cards (models 2600 and 4780). I have read
"out there" that there are ATI issues with VMD. True?

This problem exists on three different Mac laptops we've tested here.
I don't have any problems displaying to my mac in my office, using
10.5.8 and XQuarts 2.4.0 on an intel mac with nVidia GeForce 7300
card. They do not have any problem when running VMD on their desktop,
only when displaying back. I suspected GLX at first, it looked like
something was up with glSwapBuffers. To test this, I tried setting
LD_LIBRARY_PATH on the remote machine so that VMD loads OS Mesa and
thus does software rendering, but this surprisingly does not eliminate
the flicker.

How to proceed to get more information? I can run in debug mode, but
don't know what to look for. I tried changing graphics settings in
the menu, but none made any difference.

/* A function that takes a single integer argument and returns
    a pointer to a function that takes two integer arguments and
    returns a floating-point number. */
float (*func2(int a))(int, int);
Rich Cook