From: John Stone (johns_at_ks.uiuc.edu)
Date: Thu Aug 10 2006 - 17:08:48 CDT

Hi Marc,
  I'm glad that helped you solve your compilation problem.

MacOS X only started supporting GLSL as of MacOS X 10.4.x,
it wasn't available on older versions of MacOS X, and since we've
been (up to this point anyway) building our VMD releases for PowerPC
on a 10.3 box, this is why it didn't show up thus far. In practice,
few of the MacOS X machines have a usable GLSL implementation for
the level of functionality required by VMD. All of the ATI-based Macs
I've tried so far end up running the shader in software emulation.
The NVidia-based Macs may do better, we'll see. I don't have an
Nvidia-based Mac to test on presently.

SDL is a portable game-oriented lightweight graphics and audio
interface toolkit which I played with before implementing the
MacOS X OpenGL window using FLTK. I haven't done much with it
since initially writing a simple SDL-based VMD display device,
it's just another DisplayDevice subclass:
  http://www.ks.uiuc.edu/Research/vmd/doxygen/classDisplayDevice.html

The FLTKOpenGLDisplayDevice is the version that is used by the
MacOS X builds of VMD, since we haven't written our own low-level
window management code, we're letting FLTK manage the OpenGL
window for us on that platform.

On Windows and Unix, we use specially written low-level window management
code in order to take advantage of advanced rendering features like
multisample antialiasing, support for video-readback based image capture
on high end graphics systems like the Sun XVR-4000, and in order to capture
input events from devices like the Spaceball, and so on.
In principle, one could use FLTKOpenGLDisplayDevice on all of the
supported VMD platforms, but for Win32 and Unix X11, we have reasons
to use our own window management code instead.

FreeVR is like the CAVE display device, it's for immersive VR
environments with multiple displays, running on multiprocessor
shared memory machines:
  http://www.freevr.org/

Let me know if you have more questions..

  John Stone
  vmd_at_ks.uiuc.edu

On Thu, Aug 10, 2006 at 11:35:36PM +0200, Marc Baaden wrote:
>
> Hi John,
>
> thanks for your thorough explanations. I was building on a pure 32-bit
> machine, and there was indeed a rogue libGL.a. Fixed now.
>
> A couple more curiosity questions:
> What do the SDL, FLTKOPENGL and FREEVR configuration options do? (Eg
> when would you need/use them?)
>
> And is the GLSL shading supported on Mac OSX (the menu doesn't show up
> when I execute the VMD 1.8.5a9 binary on my Mac -- I haven't tried to
> build a Mac version myself)?
>
> Thanks,
> Marc
>
> >>> John Stone said:
> >>
> >> Hi Marc,
> >> It appears you have some kind of problem with the OpenGL libraries you
> >> linked your build against, since you're getting that warning:
> >> "Xlib: extension "XFree86-DRI" missing on display ":0.0"."
> >>
> >> That seems to indicate to me that you may have inadvertently linked with a
> >> bad OpenGL library or something of that sort. [..]
> >> If you're doing the build on a purely 32-bit machine, then it may be that
> >> you've go a rogue libGL.a or libGL.so on your system in a place that your
> >> own compiled binary is linking/finding, but ours is ignoring.
> --
> Dr. Marc Baaden - Institut de Biologie Physico-Chimique, Paris
> mailto:baaden_at_smplinux.de - http://www.baaden.ibpc.fr
> FAX: +33 15841 5026 - Tel: +33 15841 5176 ou +33 609 843217
>

-- 
NIH Resource for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
Email: johns_at_ks.uiuc.edu                 Phone: 217-244-3349
  WWW: http://www.ks.uiuc.edu/~johns/      Fax: 217-244-6078