VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Tue May 18 2004 - 09:21:44 CDT

Hi Eugen,
  Regarding various methods for volume rendering, the openqvis package
you reference appears to be a hardware accelerated implmentation that
immitates a ray casting method as far as the type of images it produces go.
At present, VMD provides isosurface extraction mechanisms and textured
slicing planes, and in VMD 1.8.3 one can also texture any molecular
representation by volumetric data (i.e. to make GRASP-like pictures
like this one:
  http://www.ks.uiuc.edu/Research/vmd/plugins/apbsrun/

I've already started working on beefing up VMD's support for
OpenGL shading language in hopes of using it to perform real-time
ray casting on volumetric datasets, provide greatly improved interactive
shading, and so on. I've already implemented a simple phong shader
for VMD that generates stunningly good looking images that still render
within 10% of the speed of standard OpenGL, but with quality that looks
more like what you'd expect from a ray tracer. Here are two example
images I've made with the current test version of VMD that illustrate
some of what I'm hoping to get out of using OpenGL Shading Language
in VMD.

Standard "Surf" image from VMD:
http://www.ks.uiuc.edu/Research/vmd/images/collections/openglshader/2004/normal.jpg

"Surf" image rendered with the new OpenGL Shading Language code in VMD:
http://www.ks.uiuc.edu/Research/vmd/images/collections/openglshader/2004/glsl.jpg
  
I have a bunch of older test images I did with an older version of the code
here as well, if you'd like to see more variety:
http://www.ks.uiuc.edu/Research/vmd/images/collections/openglshader/2003/jpeg/

I haven't implemented a ray caster for rendering volumetric datasets yet,
but that's definitely on the list of things I want to do eventually. :-)

  John Stone
  vmd_at_ks.uiuc.edu

On Tue, May 18, 2004 at 11:05:48AM +0200, Eugen Leitl wrote:
> On Tue, May 18, 2004 at 12:58:22AM -0500, John Stone wrote:
>
> > I'm still thinking about how to deal with time varying volumetric datasets
> > in a semi-graceful way. They are much more computationally demanding to
> > animate than trajectories are, so doing something useful with time varying
> > volumetric data may require taking a different approach than has been taken
>
> Are you going to support true volumetric rendering, using
> http://openqvis.sourceforge.net/ or software-only rendering?
>
> > in VMD thus far. You're not the only one to ask for this, so its probably
> > inevitable that we'll need it at some point, I'm just not certain how best
> > to allow this sort of thing presently.
>
> --
> Eugen* Leitl leitl
> ______________________________________________________________
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-- 
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