VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Thu Dec 14 2000 - 12:45:27 CST

Hi Lothar,
  Sounds good, just one question: Which versions of POV-Ray support
this camera model? We try to be somewhat conservative with use of
"new features" in 3rd party programs as it seems that most of our users
are using older versions of software like POV. We may want to split up
the POV rendering code in VMD to output for either new or old versions
if this keyword isn't available in the previous revs.

Thanks,
  John Stone
  vmd_at_ks.uiuc.edu

On Thu, Dec 14, 2000 at 11:57:57AM -0600, Lothar Esser wrote:
> On Thu, 14 Dec 2000, John Stone wrote:
> > Hi,
> > You are absolutely correct. As far as I know there isn't a way to
> > specify an orthographic camera in POV-Ray, if there is, we just need to
> > be made aware of this and we can write code for VMD that will do it.
> > As far as we currently know though, POV doesn't have an orthographic camera
> > capability. (We're not POV experts though, so if someone knows a good way
> > of doing an orthographic camera in POV, we're all ears...)
>
> Well it is in the povray documentation : the projection type of a camera
> can be perspective, orthographic, fisheye, ultra_wide_angle, omnimax ...
> so it is just one keyword you have to add :
>
> camera {
>
> orthographic
> ....
>
> }
>
>
> >
> > You can probably "fake" an orthographic camera by moving the camera
> > position 10 times farther away from the molecule, and then increasing
> > its "zoom" (or decreasing the size of the image plane) by a factor of
> > ten. This isn't really an orthographic view, but it significantly
> > reduces the apparent perspective, using factors larger than 10 reduces
> > the perspective even further. An orthographic view is basically the same
> > as a perspective view where the camera is infinitely far away and zoomed
> > in "infinitely". Most renderers have some sort of limit or beging to lose
> > numerical precision somewhere on the way to infinity, so the technique doesn't
> > completely accurately approximate an orthographic view, but its better
> > than nothing. Factors of 10 and 20 ought to work pretty well without
> > messing up the numerical precision of most renderers.
> >
>
> I use the same technique to get a pseudo orthorgraphic view only that I
> move about 100 times farther away using a camera angle of about 0.4
> degrees. This gives me more flexibility in programming - at least this is
> what I believed.
>
> IMHO it should be easy to implement an orthographic camera in vmd for
> povray renditions.
>
>
> Lothar Esser
> 

-- 
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