Fitted FFD generation

[sseraj]

Purpose

This PR adds a function for generating fitted wing FFDs. The function uses DVCon to perform surface projections, which was @anilyil's idea. @ArshSaja made the initial implementation.

Here is an example of a C172 wing FFD

I added the function to a file named ffd_generation.py and also moved write_wing_FFD_file to this file because I thought it was more appropriate than file_io.py.

Expected time until merged

A week or possibly more if reviewers want to test it out on their own geometries

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #139 (d3ef8fa) into main (cad9040) will increase coverage by 0.14%.
The diff coverage is 84.03%.

@@            Coverage Diff             @@
##             main     #139      +/-   ##
==========================================
+ Coverage   62.62%   62.76%   +0.14%     
==========================================
  Files          45       46       +1     
  Lines       11213    11262      +49     
==========================================
+ Hits         7022     7069      +47     
- Misses       4191     4193       +2     

Impacted Files	Coverage Δ
pygeo/constraints/DVCon.py	71.72% <ø> (+0.88%)	⬆️
pygeo/geo_utils/file_io.py	37.83% <ø> (-17.97%)	⬇️
pygeo/geo_utils/ffd_generation.py	83.89% <83.89%> (ø)
pygeo/geo_utils/__init__.py	100.00% <100.00%> (ø)

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[ArshSaja]

Nice work @sseraj . Thank you for adding it

[marcomangano]

Neat implementation! I just have one comment:

[marcomangano]

I am a bit confused about the usage of relative and absolute margins even after checking out the implementation. What's the rationale? A one-line explanation in the docstrings above would help.

[joanibal]

How fitted are the FFDs? Can you post a picture of the embedding volume and with the points inside?

[ArshSaja]

This is the previous example I had.

[sseraj]

How fitted are the FFDs? Can you post a picture of the embedding volume and with the points inside?

The fit will depend on the user-specified margins, so some manual tuning is required. For the C172 FFD, here is the embedded volume (blue) and the surface points.