VMD-L Mailing List

From: Lothar Esser (esser_at_chop.swmed.edu)
Date: Thu Dec 14 2000 - 11:57:57 CST

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