[Chimera-users] Wall eye stereo has no depth in orthographic projection

Conrad Huang conrad at cgl.ucsf.edu
Thu Oct 19 11:21:24 PDT 2017

Hi, Boris.

I wrote the stereo code a VERY long time ago and I think several others 
have changed various parts since.  Still, I'm a little surprised that 
the distance to screen has any effect in orthographic projection.  In 
perspective projection, the parameter obviously makes a big difference. 
In code, all three stereo parameters in the Camera tab are combined to 
determine the effective field of view, and therefore the depth effect.

Rather than playing with those numeric parameters, you can also use the 
Side View tab to get immediate feedback on changes.  The documentation 
for Side View 
describes the various controls, but here is a short summary.  Switch 
from "right" to "top" view by changing the "Side:" option just above the 
Help button, then choose a stereo mode (e.g., wall-eye stereo) by double 
clicking on the eye and selecting from the menu.  That should show a 
rectangular eye with separate viewing regions for the left and right 
eyes, depicted by red lines.  These red lines are draggable and the 
graphics view should immediately reflect changes so you can 
interactively choose your preferred field of view/depth effect.  The 
eye, yellow hither and yon clipping plane lines, and the dotted focal 
plane line are also draggable (left-right) to control the view size, 
depth-cue effects, and front-back positioning respectively.

Hope this helps.


On 10/19/2017 10:38 AM, Boris Steipe wrote:
> Thanks Conrad - has this always been coded this way? I seem to remember that I used orthographic mode (years? ago) when the perspective mode overemphasized depth - which is what I was trying to solve in the first place.
> Thus the workaround seem to be to increase the distance to screen in orthographic mode - something like 80cm gives me about the right depth-to-width ratio on B-DNA.
> Cheers,
> Boris
>> On Oct 19, 2017, at 1:23 PM, Conrad Huang <conrad at cgl.ucsf.edu> wrote:
>> Stereo views derive from binocular vision where the left and right eyes see slightly different orientations of the same scene.  Perspective projects approximates the positions of the two eyes and generate two images that differ by a shearing transformation, and you get the stereo effect.  Orthographic projection effectively places the eye infinitely far away in the viewing direction, so the views for left and right are identical, and you do not get the stereo effect.  Thus, stereo viewing and orthographic projection are inherently incompatible and should not be used together.
>> Conrad
>> On 10/19/2017 8:04 AM, Boris Steipe wrote:
>>> Hello -
>>> When viewing a molecule in wall-eye stereo and orthographic projection, the scene is "flat", i.e. the L and R images are identical. Perspective projection works as expected.
>>> Is there a workaround?
>>> Chimera 1.12 (41617)
>>> Mac OS X 10.11.16, NVIDIA GeForce GT 750M
>>> Thanks!
>>> Boris
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