[FIX] Fix aspect ratio in surface plotting

[NicolasGensollen]

Fixes #2658

WIP...

Example

For plot_surf:

import hcp_utils as hcp
from nilearn import plotting, surface

surf = surface.load_surf_mesh(hcp.mesh.flat)
plotting.plot_surf(surf)

Now gives:

TODO: Fix view_surf which, as pointed out by @jeromedockes, suffers from the same problem although it relies on a different machinery.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d3caac1) 88.63% compared to head (ff34a75) 88.61%.
Report is 808 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2899      +/-   ##
==========================================
- Coverage   88.63%   88.61%   -0.02%     
==========================================
  Files         101      101              
  Lines       13818    13830      +12     
  Branches     2688     2690       +2     
==========================================
+ Hits        12247    12255       +8     
- Misses        979      983       +4     
  Partials      592      592              

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[bthirion]

At least, the fix for plot_surf seems good.

[NicolasGensollen]

Update: ea0f01e proposes a possible fix for view_surf. If you test it with:

import hcp_utils as hcp
from nilearn import plotting, surface

surf = surface.load_surf_mesh(hcp.mesh.flat)
plotting.view_surf(surf)

You should get:

With the problem of the initial zoom that still need to be fixed. That is, initially the figure looks like this:

and you have to zoom out.

[bthirion]

I still have the problem with the initial zoom.

[NicolasGensollen]

I still have the problem with the initial zoom.

Weird... 🤔
Do you still have the issue now? I changed the cameras settings and the examples in the artifacts look good now.

[bthirion]

LGTM now.

[bthirion]

LGTM. Maybe a small whatsnew entry ?

[jeromedockes]

the problem is that now the brain is too small and too far from the colorbar when plotting a surface map on a mesh in mni space (or close to it), which is the vast majority of use cases:

before:

now:

I don't think deteriorating the plots for the most common use case to address an edge case is the way to go. maybe we should allow users to control the zoom (although they can do it with the mouse once the interactive plot is opened, and maybe further programmatic customization of the plots should be deferred to after #2902 is merged)

otherwise the fix to control the aspect ratio looks good!

[ymzayek]

I can take this one over. It is still an issue and concluding from what is done here I would keep the aspect ratio fix for both plot_surf and view_surf but remove the changes in the camera settings. There will still be the problem of the initial zoom for view_surf being too big for this use case but the user can zoom out.

[Remi-Gau]

• Closing in favor of [FIX] Fix aspect ratio for flat maps #4184.