Add vtk to build visualization

[Tobias-Fischer]

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Reset the build number to 0 (if the version changed)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[Tobias-Fischer]

This is needed to build rtabmap in the RoboStack project
/cc @wolfv @traversaro

[Tobias-Fischer]

@conda-forge-admin, please rerender

[Tobias-Fischer]

@conda-forge-admin, please rerender

[Tobias-Fischer]

@conda-forge-admin, please rerender

[hobu]

I'm worried that VTK and QT dependencies of PCL are going to make it difficult to bump versions and rerender in the future. VTK and QT (QT especially) are not upgraded at their normal release pace in Conda/Forge.

I don't know if it is possible to create a sub package or something that makes this part of PCL optionally installed. It is probably a lot more effort than it is worth.

[Tobias-Fischer]

We can create two variants, one with QT/VTK and one without. I'll try getting it to build first, and then introduce the variant.

[hobu]

If it is a big hassle don't worry about it.

[Tobias-Fischer]

@conda-forge-admin, please rerender

[Tobias-Fischer]

Is there some way to enforce pulling in the most recent build? Osx fails because it pulls in the previous build of vtk (build num 6), not the very latest build (build num 7)

[Tobias-Fischer]

@conda-forge-admin, please rerender

[Tobias-Fischer]

Hi @hobu @chambbj,
This is now ready for your review. It adds support for the visualization subsystem by enabling the WITH_OPENGL, WITH_QT and WITH_VTK flags. To enable building with VTK9, a patch is included from PointCloudLibrary/pcl#4262 that is already merged upstream.

It would be great if you could have a look and let me know what you think.

[chambbj]

I'm fine with this. Objections @hobu?

[chambbj]

@Tobias-Fischer I guess I will only add that it could be helpful to cross-reference the patch to the PCL fix so that it is a little more obvious when we can back out the patch. E.g., patch 4540 corresponds to PointCloudLibrary/pcl#4540 and has yet to be merged. I'll be honest, we clearly haven't been great about watching these, but it could help down the road.