Polygonal 2D poloidal plots

[mikekryjak]

xBOUT's default pcolormesh() method creates plotting artifacts around the X-point due to having to plot the grid on a per-region basis and not having corner information.

This new method uses a different approach, and is more like what UEDGE, SOLEDGE2D and SOLPS users do. Using coordinates of cell centres and cell corners, a Matplotlib Polygon is created for each cell independently and put into a PatchCollection . With each cell being independently plotted, there are no issues arising from the poloidal ordering of the cells or from the X-point.

The polygon plotting routine was adapted from this PR which was itself based on a UEDGE routine. The cell corners were obtained using this Hypnotoad PR. It adds a new plot method accessed by da.bout.polygon() which creates fast, pretty 2D plots without visual artefacts around the X-point.

• Add facility to read the cell corners into dataset coords in geometry.py
• Create plot2d_polygon in plotfuncs.py
• Test on single null
• Make sure it works when plotting with guard cells as well as without

Decided to not integrate it with plot2d_wrapper as polygon doesn't plot on a region basis and does not wrap Xarray plot routines.

There is an additional improvement where I fixed the colorbar to be always exactly the height of the plot using a hack from https://joseph-long.com/writing/colorbars/.

I also changed the default style - I disabled the targets and limiter hatching and made the separatrix a continuous thin white line. I personally think this is a cleaner look, but I understand this is personal preference. If anyone has strong feelings about this I'm happy to make the previous look the default.

Example output:

[codecov-commenter]

Codecov Report

Merging #280 (5391d64) into master (212b407) will decrease coverage by 1.24%.
The diff coverage is 4.76%.

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@@            Coverage Diff             @@
##           master     #280      +/-   ##
==========================================
- Coverage   68.94%   67.71%   -1.24%     
==========================================
  Files          15       15              
  Lines        3214     3277      +63     
  Branches      792      808      +16     
==========================================
+ Hits         2216     2219       +3     
- Misses        734      793      +59     
- Partials      264      265       +1     

Impacted Files	Coverage Δ
xbout/geometries.py	68.87% <0.00%> (-1.08%)	⬇️
xbout/plotting/plotfuncs.py	16.19% <1.75%> (-2.48%)	⬇️
xbout/boutdataarray.py	78.20% <50.00%> (-0.16%)	⬇️
xbout/region.py	83.59% <100.00%> (+0.03%)	⬆️

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[pep8speaks]

Hello @mikekryjak! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file xbout/plotting/plotfuncs.py:

Line 886:89: E501 line too long (90 > 88 characters)
Line 894:89: E501 line too long (103 > 88 characters)
Line 914:89: E501 line too long (90 > 88 characters)
Line 935:23: E711 comparison to None should be 'if cond is None:'
Line 938:22: E711 comparison to None should be 'if cond is not None:'

• In the file xbout/plotting/utils.py:

Line 124:89: E501 line too long (116 > 88 characters)

• In the file xbout/tests/test_against_collect.py:

Line 223:37: E701 multiple statements on one line (colon)

• In the file xbout/tests/test_load.py:

Line 475:5: E704 multiple statements on one line (def)
Line 625:5: E704 multiple statements on one line (def)

Comment last updated at 2024-05-28 15:22:58 UTC

[mikekryjak]

This is ready for review & merge