[vtk-developers] Strange behavoir in vtkCamera

[Lisa Avila]

Hi Chris,



>Lisa-
>   Since this flag affects the interpretation of the ViewAngle value, I
>didn't think the parallel case was relevant, since  a "view angle" is an
>inherently perspective concept, is it not?

ViewAngle is for perspective and ParallelScale is for parallel.  In the 
same way that the view angle represents what you see in Y, the parallel 
scale represents how much you see in Y. The method  name maybe could be 
more generic than UseHorizontalViewAngle, but I don't think it makes sense 
to support this for perspective and not for parallel.

> > I suspect this is a bug and I
> > will correct it.
> > I am suspicious of this change - there are places outside of
> > vtkCamera that
> > assume that the field of view defines the angle in Y and
> > unless all of
> > these were changed as well then it is likely that using the
> > horizontal flag
> > will result in bad images.
>
>   Yes, there are changes that need to be done to vtkRenderer.cxx to ensure
>correct behavior of ViewToWorld and WorldToView.


Actually there is more than that - for example, vtkWindowToImageFilter 
would need to be modified since it assumes that the ViewAngle represents a 
Y angle when determining how to tile an image. I am sure there are other 
classes that would need modifications too (probably including some of the 
importer/exporters).

I think that since this change is only half implemented, it should be 
removed from VTK until it can be fully implemented.


Lisa