[vtk-developers] New Stereo Mode

[Thomas Hansen]

I have modified the vtkRenderWindow class and added a new stereo mode [3].
 The stereo mode displays the left and right images next to each other
for use with our stereoscopic visualization environment (SVEN) [1].
Our setup consists of two projectors and a set of polarised lenses;
it is very much similar to the Geowall project [2].

I had monitored the vtk-users list for quite a while and had found
some posts in the archives from users looking for this functionality,
and finally decided to just implement it.  I am aware that the same
effect is achievable by using the CrystalEyes mode with a quad
buffered video card.  However we are trying to keep the budget low,
and the modifications now allow vtk and our setup to work with any
dual-head graphics card.

Currently the new stereo mode works fine, but is implemented in a
rather inefficient way.  I looked at how the other stereo modes were
implemented and used them as somewhat of a template; which brings up
my main concern:  The current implementation kind of chops half of
both images off and places the remains next to each other.  That of
course causes both images to be rendered at twice the width of what
would actually be required (Which is quite noticeable when the window
spans two full screens).  Also, to obtain correct results, I am
currently relying on the phenomenon that the size of the rendered
objects (zoom factor?) is changes only based on the heigth of the
window and not the width (A quarter of each image is cut off on both
sides).  I would like to make sure that this is a feature of the vtk,
and not some strange coincidence.

I have thought of some alternative ways to get around this problem,
including writing an entirely new subclass of vtkRenderWindow, but at
the same time I would like to stick close to the API with regard to
how the other stereo modes are used.  Also there might be easier ways
to control the size of the images being rendered without breaking
anything else?  I really just started using the vtk, and have looked
at the Renderer classes, but cant find a way to trick them into
rendering half width of the RendererWindow.

I would greatly appreciate any comment, concerns or genius ideas on
how to easily fix this.

Thanks;
  -Thomas Hansen <thomas.hansen at wartburg.edu>

[1] http://mcsp.wartburg.edu/SVEN/
[2] http://geowall.geo.lsa.umich.edu/

[3] The files were to big for teh mailing list i guess, so i put them online:

  http://thomas.3kings.de/vtk/vtkRenderWindow.cxx 
  http://thomas.3kings.de/vtk/vtkRenderWindow.h