From: John Stone (johns_at_ks.uiuc.edu)
Date: Thu Jan 05 2012 - 14:08:48 CST

Hi Ajasja,
  Thanks for the example images. The angle dependent artifact
you observed is not unique to the QuickSurf representation, it is due
to a limitation in the order-dependent OpenGL transparency implementation
used in VMD when GLSL is enabled. For the time being, to get perfect renderings
of transparent representations, you should use Tachyon or one of the other
ray tracing image rendering methods. I plan to implement an order-independent
transparency feature for GLSL rendering in VMD, but it will be in a subsequent
version of VMD due to the significant amount of testing that has to be
performed to ensure it will work with low-end GPU hardware.

I will have a look at the "sphere-lines" issue you observe when culling is enabled,
that might be easy for me to fix for VMD 1.9.1, I'll let you know what I find out.

Cheers,
  John Stone
  vmd_at_ks.uiuc.edu

On Wed, Jan 04, 2012 at 08:52:28PM +0100, Ajasja Ljubeti?? wrote:
> Can you provide some example images that show the artifact you refer
> to?
>
> Of course. I already included hyper-links to the images, but they seem to
> have disappeared.
> Culling artefact (example 1 and 2)
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/culling1.png
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/culling2.png
> other side (in the oposite direction of the z axis)
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/culling-ok.png
> no culling:
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/no-culling.png
> For the Quicksurf representation artefacts (horizontal "sphere-lines" at
> the top):
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/quicksurf1.png
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/quicksurf2.png
> If the view angle changes the artefacts disappear:
> http://lbf.ijs.si/ajasja/mails/VMD-quicksurf/quicksurf-ok-1.png
> Best regards,
> Ajasja
>
> Cheers,
> John Stone
> johns_at_ks.uiuc.edu
> On Wed, Jan 04, 2012 at 12:28:06PM +0100, Ajasja Ljubeti?? wrote:
> > Oh, and if I enable culling and look on my ions from below (along
> the z
> > axis) theyA disappear.
> > Example1 Example2. If I turn culling offA or look from theA other
> side (in
> > the oposite direction of the z axis) the spheres stay visible.
> > Best regards,
> > Ajasja
> >
> > On Wed, Jan 4, 2012 at 12:08, Ajasja LjubetiA:*
> > <ajasja.ljubetic_at_gmail.com> wrote:
> >
> > Dear all,
> > I really like the new quicksurf representation. As the name
> implies it's
> > *really* quick (realtime on my GTX570).
> > But I noticed some renderingA artefacts that are view angle
> dependant
> > and show up when the view vector is in the xy plane.
> > SomeA examples. If I change the view slightly everything is OK.
> > I'm running Win7 64 bit SP1 with the 285.86 NVIDIA drivers.
> > Best regards,
> > Ajasja Ljubetic
> > YoungA researcher,
> > Laboratory of biophysicsA
> --
> NIH Resource for Macromolecular Modeling and Bioinformatics
> Beckman Institute for Advanced Science and Technology
> University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
> http://www.ks.uiuc.edu/~johns/ Phone: 217-244-3349
> http://www.ks.uiuc.edu/Research/vmd/ Fax: 217-244-6078

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