Add 3D orthogonal structure mesh type for mesh generators.

[RyanWollaeger]

Background

• The X3D parser supports parsing 3D meshes, but there is no generator for X3D files of 3D meshes in Draco.
• x3d_generator supports 3D file output, so what is needed is a 3D mesh type in mesh_types.py

Purpose of Pull Request

• Add a simple orthogonal structured mesh type, to generate corresponding unstructured data.

Description of changes

• Add orth_3d_mesh class to mesh_types.py.
• Add orth_3d_mesh as an option to x3d_generator.py.
• Test 1-cell result of orth_3d_mesh in X3D parser unit test.

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • Travis/Appveyor CI checks pass
  • Code coverage does not decrease
  • Valgrind test passes
  • Toss3 checks pass
  • Trinitite checks pass
  • Code reviewed/approved, sufficient DbC checks, testing, documentation

[codecov]

Codecov Report

Merging #1091 (171b589) into develop (bccfce4) will increase coverage by 0.0%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           develop   #1091   +/-   ##
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  Coverage     88.7%   88.7%           
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  Files          374     374           
  Lines        18591   18592    +1     
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+ Hits         16495   16496    +1     
  Misses        2096    2096           

[RyanWollaeger]

Sorry - forgot to run flake8 on this before submitting - will do so shortly.

[RyanWollaeger]

I should probably add a comment on how to use the x3d_generator script, e.g.:

To create X3D files for a 4x4x4 3D orthogonal structured mesh on domain (x,y,z) in [0,1]x[0,2]x[0,4]:

$ ./x3d_generator.py --mesh_type orth_3d_mesh --num_per_dim 4 4 4 --bnd_per_dim 0 1 0 2 0 4

[KineticTheory]

I should probably add a comment on how to use the x3d_generator script, e.g.:

To create X3D files for a 4x4x4 3D orthogonal structured mesh on domain (x,y,z) in [0,1]x[0,2]x[0,4]:

$ ./x3d_generator.py --mesh_type orth_3d_mesh --num_per_dim 4 4 4 --bnd_per_dim 0 1 0 2 0 4

Can you add this to a README.md file in the python subdirectory?

[RyanWollaeger]

I should probably add a comment on how to use the x3d_generator script, e.g.:

To create X3D files for a 4x4x4 3D orthogonal structured mesh on domain (x,y,z) in [0,1]x[0,2]x[0,4]:

$ ./x3d_generator.py --mesh_type orth_3d_mesh --num_per_dim 4 4 4 --bnd_per_dim 0 1 0 2 0 4

Can you add this to a README.md file in the python subdirectory?

Good idea - will do!

[KineticTheory]

The markup linter flagged a couple issues with the README.md. Those should be easy to fix.

[RyanWollaeger]

The markup linter flagged a couple issues with the README.md. Those should be easy to fix.

Thanks @KineticTheory - just tried to fix these.

[RyanWollaeger]

Sorry - I missed one linter error - fixing now.

[KineticTheory]

If those lint warnings are confusing, here's the scoop: https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md

[KineticTheory]

This might be useful? https://dlaa.me/markdownlint/
I'm not sure if it uses the same rules that we have.

[RyanWollaeger]

If those lint warnings are confusing, here's the scoop: https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md

This is a useful reference - thank you!