[vtkusers] vtkAppendPolydata - wrong extents on multiple inputs

[Dan Lipsa]

Nigel,
The pipeline executive compares the modification time (vtkObject::GetMTime())
for the output of a filter against each of its inputs. If any of the inputs
is newer, the filter is updated. It may be that your filter does not update
the time of its output properly. This request is propagated upstream and
stops if a filter has its inputs older than its output. I would setup a
breakpoint and look at the first update for your filters.

On Thu, Aug 6, 2015 at 9:20 AM Nigel Mcfarlane <Nigel.Mcfarlane at beds.ac.uk>
wrote:

> Dear vtkusers,
>
>
>
> I am creating a visual pipe in vtk 6.2.0 and I am having problems
> connecting vtkAppendPolyData to multiple inputs which start from images of
> different dimensions.  The visual pipe converts a set of input images into
> isosurfaces, adds scalars for colour and transparency, then merges them
> into one polydata mesh so they can be depth sorted before rendering.  Its
> structure looks like this:
>
>
>
> //
>
> //     image1       image2       image3
>
> //       |            |            |
>
> //    DMCubes1     DMCubes2     DMCubes3
>
> //       |            |            |
>
> //  AddScalars1  AddScalars2  AddScalars3
>
> //             \      |      /
>
> //              \     |     /
>
> //               \    |    /
>
> //            vtkAppendPolyData
>
> //                    |
>
> //           vtkDepthSortPolyData
>
> //                    |
>
> //               Mapper/Actor
>
> //                    |
>
> //                 Renderer
>
> //
>
>
>
> The images are produced by vtkMetaImageReader, the “DMCubes” filters are
> vtkDiscreteMarchingCubes, and the”AddScalars” filters are my own code.
>
>
>
> The problem is that this produces an image in which the dimensions/extents
> of two of the images have clearly been set incorrectly.  I don’t know much
> about the way the vtk pipeline works, but I suppose that an information
> request for the extents of the images travels up and back down the
> pipeline, so the extents get set to that of the last input, and then
> applied to all the inputs.  The problem disappears if the input branches
> are first independently updated by calling a manual Update() on each of the
> AddScalars filters, but it returns if one of the DMCubes filters is
> modified, which triggers another general update cycle.
>
>
>
> Is there any way to set up this pipeline so that it does not require a
> manual update when the image inputs are modified?
>
>
>
> Nigel McFarlane
>
> University of Bedfordshire
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