WIP: Add VisPy 3d backend

[GuillaumeFavelier]

What does this implement/fix?

The goal of this PR is to add a VisPy-based 3d backend to the visualization capabilitites of MNE.

Additional information

It is a work in progress, some features are still missing or incomplete as of now.

[codecov]

Codecov Report

Merging #5925 into master will increase coverage by 0.01%.
The diff coverage is 88.69%.

@@            Coverage Diff             @@
##           master    #5925      +/-   ##
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+ Coverage   89.26%   89.28%   +0.01%     
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  Files         411      412       +1     
  Lines       74691    74966     +275     
  Branches    12341    12390      +49     
==========================================
+ Hits        66676    66930     +254     
- Misses       5151     5156       +5     
- Partials     2864     2880      +16

[GuillaumeFavelier]

For reference, the difference between the two backends for the parametrized function test_3d_backend() in mne/viz/backends/tests/test_renderer.py:

With Mayavi (default):

With VisPy (work in progress):

[larsoner]

This pull request introduces 1 alert when merging 7fdceda into 7856133 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[agramfort]

@GuillaumeFavelier you'll need to update the CIs script to start testing vispy. I would see if you can update one travis build so it uses vispy

[larsoner]

I would just update environment.yml (pip section) and requirements.txt to include vispy, it will fix CircleCI, Travis, and AppVeyor.

[larsoner]

This pull request introduces 1 alert when merging 2a4b50b into 5a0bbee - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging 18d355c into 8b00fc9 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging e122460 into 8b00fc9 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging 8c96428 into b535a53 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging 1ff3d15 into 5537ba2 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[GuillaumeFavelier]

ToDo list:

• Modify the set_camera() function based on vispy to use the same reference than mayavi
• Allow scaling of the quiver3d() with the scalar values
• Add support for user-given colormap
• Projection class

After the rework on the quiver3d, text and the isolines this is the current result:

With Mayavi (default):

With VisPy (work in progress):

[GuillaumeFavelier]

About the shading of the spheres, I can use visuals.Mesh instead of visuals.Sphere but a related PR is already opened in vispy.

[larsoner]

This pull request introduces 1 alert when merging d7ec52b into 0990196 - view on LGTM.com

new alerts:

• 1 for Unused import

---

Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging 46b4565 into 7c21bd6 - view on LGTM.com

new alerts:

• 1 for Unused import

---

Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging 2361e47 into 571a792 - view on LGTM.com

new alerts:

• 1 for Unused import

---

Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging e0a8894 into 925423c - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging a1f12ce into 297422c - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

This pull request introduces 1 alert when merging b3db935 into c4a83c5 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[lgtm-com]

This pull request introduces 1 alert when merging af8bb0b into 5d80e26 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[lgtm-com]

This pull request introduces 1 alert when merging f28c21d into 5d80e26 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[lgtm-com]

This pull request introduces 1 alert when merging 3904d70 into f26d816 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[lgtm-com]

This pull request introduces 1 alert when merging d2ba8c2 into 5803738 - view on LGTM.com

new alerts:

• 1 for Unused import

---

Comment posted by LGTM.com

[lgtm-com]

This pull request introduces 1 alert when merging 4a6d73a into 62c0af8 - view on LGTM.com

new alerts:

• 1 for Unused import

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Comment posted by LGTM.com

[larsoner]

@GuillaumeFavelier what are the blockers / todos here? Do we still want this backend?

[agramfort]

I would say pause and let's focus on a light vtk backend that also works with vtk-js in a notebook

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