[vtkusers] Problem with polydatas sharing vtkPoints in vtk8

Sean McBride sean at rogue-research.com
Wed Jan 30 12:20:34 EST 2019

On Thu, 24 Jan 2019 10:28:07 -0200, Tiago Nobrega said:

>I'm trying to update from vtk 7.0 and I'm having an issue with a particular
>setup of polydatas. In my case I have a single vtkPoints that is shared by
>multiple vtkPolydatas, where each polydata renders a different set of
>cells. I can't get the rendering to show more than one polydata at a time
>in vtk 8.0 and up, but it works as expected in vtk 7.1. In all cases I am
>using the new OpenGL2 backend.
>I created a minimal example that reproduces the issue for me:
>https://gist.github.com/tigarmo/c90ff07a1b63bbcf396fa4aaf1e824a9 . It tries
>to show 2 quads, where each quad is a cell in a different polydata, but
>both polydatas share the same vtkPoints. This shows 2 quads as expected (by
>me) in vtk 7.1 but only 1 quad in vtk 8.0.1, 8.1.0 and 8.1.1. A surprising
>detail is that which quad is shown varies depending on the run. Sometimes
>it's the left one, sometimes the right one.
>Does anyone have any suggestions? Is this a bug? Could it be related to
>improvements in VBO caching that I saw in 8.0's changelog?


Since no one seems to have a better answer for you, what you could do is use 'git bisect' to find exactly which commit between 7.1 and 8.0 caused this change in behaviour.  The commit message will hopefully shed light on the cause and whether it's a bug or not.


Sean McBride, B. Eng                 sean at rogue-research.com
Rogue Research                        www.rogue-research.com 
Mac Software Developer              Montréal, Québec, Canada

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