VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Wed Mar 08 2000 - 15:04:34 CST

On Wed, Mar 08, 2000 at 09:43:38PM +0100, Bogdan Costescu wrote:
>
> Dear VMD Developers,
>
> After almost a month without getting any answer, I took some ours to look
> at the code and see why Crystal Eyes Stereo is no longer working on our
> O2s.

We weren't able to provide any help on this because we don't have
access any O2's that can do stereo at all.

> The answer is that in OpenGLDisplayDevice.C, glXChooseVisual or FORMS
> equivalent fl_glwincreate with configuration3[] returns NULL... But if I
> define it as:
>
> static int configuration3[] =
> {GLX_DOUBLEBUFFER, GLX_RGBA, GLX_DEPTH_SIZE, 16, GLX_STEREO,
> GLX_RED_SIZE, 4, GLX_GREEN_SIZE, 4, GLX_BLUE_SIZE, 4, None};
>
> meaning that I reduce the size of GLX_RED_SIZE (and others) from 8 to 4,
> everything works correctly.

So you're running in 12-bit color???
What does xdpyinfo tell you about your screen?

> VMD 1.3 had no size related attributes, so it worked correctly. Now the
> question is: is this size of 8 really necessary? The multisampling
> configurations are for both 4 and 8, why is the normal configuration only
> for 8?

The size requirement of "8" simply means that VMD wants 256 levels of
intensity for each of the Red, Green, and Blue color channels, which is
24-bit color. We had to change this because we got a bunch of email from
other users whose machines were choosing very poor video modes when VMD
did not specifically request 24-bit color. (Some were O2's in fact....)

Now that we know that your O2 will actually run correctly if we
only request 12-bit color, I will make a new rev of OpenGLDisplayDevice
that tries additional display modes before giving up, but there's still
a real problem here, and maybe some of the VMD user community would
care to comment:
 
If you have a machine that will support both 24-bit color without stereo,
or 12-bit color WITH stereo, which mode would you want VMD to "prefer"???
Presently, there is no mechanism for VMD to know which of those two options
the user would prefer. I can certainly modify VMD to choose all
stereo-capable modes as being preferred to non-stereo modes, but this may
not be what the majority of users want. Comments anyone?

  John 

-- 
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