Perspective vs parallel projection

[Paul Hsieh]

Hi all:

Is there a way to "synchronize" the perspective and parallel projections
when it comes to zooming and dollying?

When I switch from perspective projection to parallel projection
(by invoking vtkCamera::SetParallelProjectionOn()), then zoom the view,
and then switch back to perspective projection, the actors in the
perspective projection are not zoomed. 

Looking at the source code, I see that zooming is done differently
for perspective and parallel projection. Is there a way to calculate
and set some camera parameters (for example, parallelScale) so that the
actors are about the same size in parallel versus perspective projection?

Or is this an ill defined problem?

Thanks.
Paul


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