[vtkusers] Strange slowness with vtkImagePlaneWidget

[Marco Sambin]

Hi all.

In my VTK6-based Java application, I am using a vtkCanvas where I display
three orthogonal vtkImagePlaneWidgets, cutting a volume loaded
through vtkImageReader2.

Everything works fine on my development machine, which is a recent and
moderately-powerful 64-bit Win 7-based machine.

For legacy-compatibility purposes, I tested this application under an older
Win XP-based Pentium 4 machine with 1 GB RAM and old Barco graphic cards,
and I obtained "strange" results:

- if I feed vtkImageReader2 with a volume made up of around 360 raw slices,
each one 512x512 pixels, then the overall rendering performances of the
view containing the three vtkImagePlaneWidgets are acceptable.

- on the other side, if I feed vtkImageReader2 with a volume made up of 90
(i.e., fewer) raw slices, each one 512x512 pixels, then the overall
rendering performances of the view containing the three
vtkImagePlaneWidgets become really poor, and I can distinguish the texture
appearing on top of each plane widget painting as two separate triangles,
given the slow rendering.

Can you guess why the rendering performance of the vtkImagePlaneWidgets are
much worse with the smaller volume w.r.t. with the larger volume?

Thanks for any hints you will give.

Best regards,

Marco
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