[Chimera-users] Stereo angle value
gregc at cgl.ucsf.edu
Tue May 2 13:17:06 PDT 2006
On Wed, 26 Apr 2006, Prof. Fabrizio Briganti wrote:
> I have not been able to find any reference to the value for the angle
> difference between Right and Left views in Stereo Images made with Chimera.
> Can you help me find it?
> Is there any way to change such angle value?
To control the viewing angle and stereo separation, chimera uses 3
distances which must be given in the same units (e.g., cm, mm, inches).
They are the distance between the viewer's eye, the distance from the eyes
to the screen, and the width of the screen. Currently, there is no GUI to
change those distances, but you can change them via a Python script, or
interactively by typing in the the IDLE dialog window (Tools / General
Controls / IDLE).
The distances are:
And they default to 2.0, 30.0, and 13.0, respectively (inches). Your
brain is amazingly good at compenstating for inaccurate values, so the
only distance that you should modify is the viewDistance. Adjusting the
view distance will change how much depth is perceived in the image -- from
either too much or too little to "just right". Small viewing distances
also give a wide-angle effect.
So typing into the IDLE window:
chimera.viewer.camera.viewDistance = 15
Will move the eye halfway to the screen and increase the angle. Smaller
values give more depth.
Another important part of stereo perception is the amount of positive and
negative parallax -- i.e., how much of the molecule is behind or in front
of the screen. By default, chimera puts the center of the molcule in the
plane of the screen for half positive and half negative parallax. The
smaller the view distance, the more likely that is too much negative
parallax to comfortably view the image, so translate the molecule away
from you to increase the positive parallax and reduce the negative
Hope this helps,
UCSF Computer Graphics Lab
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