prepared a more meaningful example of tvtk usage in Mayavi

[marekyggdrasil]

Hi all!

I have been struggling with tvtk usage in Mayavi, detail on why are provided in this question (which is answered now).

I figured a more meaningful example could be useful. The previous scene was:

And now it is:

I believe it is better because:

1. This example teaches how to place glyphs in different orientation.
2. Teaches how to render a cylinder and adjust its resolution.
3. Cylinder is more visually meaningful than a sphere because of lack of spherical symmetry - orientation matters.
4. It is more visually meaningful if glyphs have different colours, it makes it provides a one more criterion helping to associate them with objects in the code.

If you need some more adjustments let me know and if you are not interested in it just close the PR. Thanks!

[marekyggdrasil]

I realised I was specifying the glyph's position by shifting its center... It is fixed now.

[codecov-io]

Codecov Report

Merging #974 (4bf9284) into master (9c12863) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #974   +/-   ##
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  Coverage   49.83%   49.83%           
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  Files         263      263           
  Lines       23927    23927           
  Branches     3259     3259           
=======================================
  Hits        11924    11924           
  Misses      11220    11220           
  Partials      783      783           

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[prabhuramachandran]

Thank you, looks good, please make the minor change I suggest and I will merge this.

[prabhuramachandran]

@marekyggdrasil -- please also rebase to current master. Thank you.

[marekyggdrasil]

@prabhuramachandran thanks for reviewing! I wrapped the lines to match the requested linting style and also merged the most recent master. No conflicts!

[prabhuramachandran]

LGTM, thanks.