[chimera-dev] stereo3D focal plane

[Tom Goddard]

Hi Matt,

  Here’s some Python that will update the focal plane position to always lie midway between near and far clip planes.

  If you zoom by moving a map or molecule closer to you (z translation) then visually the map should move from behind the screen to be in front of the screen so it looks like it is coming closer.   In other words the map moves forward and the focal plane that defines the position of the screen stays fixed.  That is normal Chimera behavior.  The above script will defeat that.  You will move the map closer to you in z, but what you will see in stereo is that the map gets bigger, but no closer.  It instead feels like a magical scaling of the map, rather than getting closer to it.  This isn’t natural, but I understand that because of the limited 3d depth with stereo viewing it is necessary to do something to avoid uncomfortable stereo where the models are too far in front of the screen.  An optimal solution is more subtle than the above script.  In fact the above script won’t prevent getting the front surface of the map too close for stereo viewing because it keeps the focal plane at the map midpoint in z.  The front of the map can still get close to your eye and the stereo will not work.  Basically you want to avoid having the front visible part of the models from getting too close to your eye where the stereo glasses don’t work (because the display screen is not wide enough).  We have not worked on techniques to avoid stereo interactive viewing limitations.  But the normal Chimera zoom uses scale factor, not z-translation, so that is the main way this problem is avoided.  But you are using z-translation instead of the normal Chimera zooming and that is why you encounter this problem.

	Tom




> On Apr 20, 2015, at 8:59 PM, Dougherty, Matthew T wrote:
> 
> I am using S3D regularly, and developed a USB user interface that allows me to adjust S3D parameters such as focal plane using a contour express dial.
> 
> I have stopped using scale factor by disabling the keyboard scroll, and switching to z translation.
> 
> I am finding that I need to adjust the focal plane a lot.​  Usually it is between the clipping planes, but when I do z translations it normally gets between the camera and the near clipping plane, or out past the far clipping plane.
> 
> For S3D animations I can work around it.  For interactive use, people are having major eye strain. 
> 
> I would like to modify the chimera code to automatically adjust the focal plane as the clipping planes change.
> 
> Can you point me to the area of code where I could make the change?
> 
> Matthew Dougherty
> National Center for Macromolecular Imaging
> Baylor College of Medicine
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