[vtk-developers] Pipeline connections that pull information but not data

[David Gobbi]

Hi All,

I'm working on a difficult problem, and would appreciate any pointers
that the pipeline experts can give me.  Some of the classes that I
contributed to VTK way back before the VTK 5 release still use some
VTK 4 pipeline mechanisms.  I've been gradually converting them to the
new executive, but I've a wall.

In vtkImageReslice there is a method called SetInformationInput(),
that allows the primary input image to be resampled to match the
"information input" image.  I implemented this by calling
UpdateInformation() on the InformationInput, so that I can pull just
the information from that input and not the data.

In the VTK 5 executive, there does not seem to be any way to establish
a pipeline connection that only pulls information.  When REQUEST_DATA
goes to the executive it is always forwarded to all inputs.  I've
tried the obvious thing, which is to set an empty UPDATE_EXTENT on the
input that I don't want any data from, but this causes a segfault.

Any ideas?

  David