From: Simon Hayhurst (simon++at++cthulhu.engr.sgi.com)
Date: 03/19/2000 19:59:11
From some work we did a few years ago in SGI Europe, we also found a huge
gain by only using hemi-spheres, and rotating the hemi-sphere to face the
user. There's a fair bit of App side workload in doing this, but since
molecules are typically moving anyway, the net win was considerable.
Ciao,
Simon
> -----Original Message-----
> From: Svend Tang-Petersen [mailto:svend++at++copen.sgi.com]
> Sent: Friday, March 17, 2000 8:18 AM
> To: Vieri Di Paola
> Cc: info-performer++at++sgi.com
> Subject: Re: Graphics algorithm
>
>
> Hi Vieri.
>
> I was actually thinking about doing excately the same for
> another project.
>
> My approch was going to be the following:
>
> 1) obtain the min and max position values for x,y,z for the
> full molecule.
> 2) generate an octree scenegraph for more efficient culling.
> (I was actually thinking about further subdivision)
> 3) foreach loaded atom place it in the 8 or even 8x8 subgraphs
> sorted by position
> 4) Foreach atom generate 3 maybe 4 LOD's to reduce the number of
> polygons rendered.
>
> It should be fairly simple.
>
>
> Vieri Di Paola wrote:
> >
> > Hello performer-list,
> >
> > I am a Biology student and wish to make a simple program
> for viewing pdb
> > molecules. As a small project, I would
> > like some information on the following matter. My project
> consists in
> > drawing spheres for each atom. My problem is that I cannot
> find any help
> > anywhere on the Internet that explains an algorithm for
> efficient >15000
> > spheres drawing. I suppose "hidden" spheres (according to a
> > certain view angle) shouldn't be drawn, etc... Does
> IRIS-performer provide
> > an efficient algorithm for the "spatial" model representation of
> > molecules?
> > Can anybody tell me exactly where to look at in the
> "performer" source
> > code examples?
> > Or can anybody tell me where (if) I can find a simple, to-the-point
> > tutorial that handles this rendering problem?
> >
> > My project can be summarized as follows:
> >
> > 1- take a set of x,y,z atom coordinates from a pdb file (simple)
> > 2- apply algorithm to "sort out" the atoms I need to draw
> according to the
> > user's viewing angle
> > 3- draw only the "visible" atoms by plotting spheres with
> the appropriate
> > Wan Der Waals radius
> > 4- update "visible" and "hidden" atoms when user rotates molecule
> >
> > I'm using FLTK (www.fltk.org) and MESA (www.mesa3d.org)
> (and hopefully
> > Iris-performer) on Linux.
> >
> > Thanks in advance,
> >
> > Vieri Di Paola
> >
> >
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> --
>
> Regards Svend
>
>
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