[vtkusers] how to handle an empty pipeline?

[Langer, Stephen A. (Fed)]

Thanks for the suggestion, but it won't work in this case.  The warning messages come from a vtkDataSetSurfaceFilter that's created as a protected member of the vtkDataSetMapper class, so I can't call vtkDataSetSurfaceFilter::AddObserver.   Subclassing vtkDatatSetMapper and overriding Render to get access to the filter would work, but feels wrong…

Is this a bug?  A warning is raised when the input to the vtkDataSetMapper is empty, except when the input type is VTK_POLY_DATA.

 -- Steve

On 10/17/17, 6:36 PM, "Bill Lorensen" <bill.lorensen at gmail.com> wrote:

    You can catch the warnings/errors like this:
    https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Florensen.github.io%2FVTKExamples%2Fsite%2FCxx%2FUtilities%2FObserveError%2F&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=Jse9qOUuZCUa9o7yU3%2FLH2HH5I0%2FlkyeL2DtyHoPjCU%3D&reserved=0
    
    
    On Tue, Oct 17, 2017 at 2:34 PM, Langer, Stephen A. (Fed)
    <stephen.langer at nist.gov> wrote:
    > Hi --
    >
    > What's the right way to handle a pipeline that might at times have no data in it?   I'm connecting to a vtkDataSetMapper,  and if the input stream is empty vtk prints a warning "vtkDataSetSurfaceFilter: Number of cells is zero, no data to process".    I don't create the vtkDataSetSurfaceFilter myself -- it's been inserted into the pipeline by the mapper.  It doesn't do that if the input data is poly data, and if I change the input to poly data, the mapper seems quite happy with the empty pipeline, so it's odd that it complains in one case but not the other.
    >
    > Is there something that I should do at the pipeline source to tell the pipeline not to run?  Is there a way to suppress just this one warning message?
    >
    > I'm using vtk 7.1.1 in C++.
    >
    > Thanks.
    >  -- Steve
    >
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