[vtkusers] how to handle an empty pipeline?

Wed Oct 18 11:26:36 EDT 2017

I don't know if it's good practice, but when there is no input data I usually do either of the followings:
- hide the actor so that no pipeline updates are requested by the renderer
- detach the data processing pipeline from the visualization pipeline (SetInputData(NULL))
- add a dummy data set (such as polydata with a single point) as input

I would be interested if there is a particular method recommended by VTK core developers.

Andras

-----Original Message-----
From: vtkusers [mailto:vtkusers-bounces at vtk.org] On Behalf Of Langer, Stephen A. (Fed)
Sent: Wednesday, October 18, 2017 11:04 AM
To: Bill Lorensen <bill.lorensen at gmail.com>
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] how to handle an empty pipeline?

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
    >
    > _______________________________________________
    > Powered by https://na01.safelinks.protection.outlook.com/?url=www.kitware.com&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=RYg%2BPlwic7Tna%2F7XBHOzzdvhkoMlxxumVNKWqExIbgs%3D&reserved=0
    >
    > Visit other Kitware open-source projects at https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.kitware.com%2Fopensource%2Fopensource.html&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=alDmSCFYyHNTCJSBl%2FfPxBQUcuQ3wtlxy%2BJkCEKzZJo%3D&reserved=0
    >
    > Please keep messages on-topic and check the VTK FAQ at: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.vtk.org%2FWiki%2FVTK_FAQ&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=YS8KxC6fI9R%2B5fACCQbDC7N3eBbFj8qy1k2SIFz%2B%2FBM%3D&reserved=0
    >
    > Search the list archives at: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmarkmail.org%2Fsearch%2F%3Fq%3Dvtkusers&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=SYRMsiT14ntcdMMbSsGahJCJavp8%2BJFOrqx%2B2x4QJ1A%3D&reserved=0
    >
    > Follow this link to subscribe/unsubscribe:
    > https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpublic.kitware.com%2Fmailman%2Flistinfo%2Fvtkusers&data=02%7C01%7Cstephen.langer%40nist.gov%7C42ff580323ed40df553608d515af87f8%7C2ab5d82fd8fa4797a93e054655c61dec%7C1%7C0%7C636438765996499743&sdata=uPalP%2BrHte%2FjsQeaMUBuxCuAOY7vv2Eye5aZHbxhIY0%3D&reserved=0

    -- 
    Unpaid intern in BillsBasement at noware dot com

_______________________________________________
Powered by https://na01.safelinks.protection.outlook.com/?url=www.kitware.com&data=02%7C01%7Classo%40queensu.ca%7Caab96158e64644f5a0a308d516399b7a%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636439359028042607&sdata=G5HjQYP%2BVtTeYvFpw2uVv8NLpIQe6H4wc1C1cxhVuy0%3D&reserved=0

Visit other Kitware open-source projects at https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.kitware.com%2Fopensource%2Fopensource.html&data=02%7C01%7Classo%40queensu.ca%7Caab96158e64644f5a0a308d516399b7a%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636439359028042607&sdata=%2Bxy3iWcIaSmwEYbuQ34qfqfv1Z6sYw6uy9TdggyCkiI%3D&reserved=0

Please keep messages on-topic and check the VTK FAQ at: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.vtk.org%2FWiki%2FVTK_FAQ&data=02%7C01%7Classo%40queensu.ca%7Caab96158e64644f5a0a308d516399b7a%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636439359028042607&sdata=wt2SqH2w2KmIFagMwyf%2BWX4VIBEJVy9Q8y3Soz8Bg0E%3D&reserved=0

Search the list archives at: https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmarkmail.org%2Fsearch%2F%3Fq%3Dvtkusers&data=02%7C01%7Classo%40queensu.ca%7Caab96158e64644f5a0a308d516399b7a%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636439359028042607&sdata=lqTS030GCguYDE%2B5gRTx%2BUS4GDeDfxL%2B1gk63C7OK%2BY%3D&reserved=0

Follow this link to subscribe/unsubscribe:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpublic.kitware.com%2Fmailman%2Flistinfo%2Fvtkusers&data=02%7C01%7Classo%40queensu.ca%7Caab96158e64644f5a0a308d516399b7a%7Cd61ecb3b38b142d582c4efb2838b925c%7C1%7C0%7C636439359028042607&sdata=XSlLpR9Hd1eQ8WY2xvZiHWeSnDQgQilkekPWN0RbkLY%3D&reserved=0