Support mesh optimization params in mesh inertial calculator

[iche033]

🎉 New feature

Summary

When //inertial/@auto is set to true, gz-sim auto computes inertial values for meshes using the MeshInertialCalculator. The calculator however uses the original mesh and ignores any //mesh/@optimization properties.

This PR extends the MeshInertialCalculator to work with optimized meshes. Main changes are:

• Switched to use the loadMesh helper function which takes care parsing the mesh SDF, loading and returning the optimized mesh.
• Use calculator to compute inertial for each submesh (as opposed to entire mesh), then sum up to get the final inertial values.

Note that the optimized meshes are stored in the MeshManager singleton, which means later when loading the physics system (which in turn needs these optimized meshes for creating collisions), it can just get the optimized meshes directly from the MeshManager cache without having to do mesh optimization again.

Test it

Here's an example of doing mesh inertial calculation for the Cordless Drill Simplified model. The mesh in this model has convex decomposition enabled, and here are the auto computed inertial values before and after the changes in this PR:

Before:

  mass: 1.61561
  xx yy zz: [0.0143132 0.0124479 0.00406482]
  xy xz yz: [0.000326503 0.00036718 -0.000947023]
  principal moments: [0.00394363 0.0125094 0.0143729]
  CoM: [-0.00637488 -0.00799589 0.222544 0 0 0]

After:

mass: 2.11133
xx yy zz: [0.0185708 0.0159216 0.0057028]
xy xz yz: [0.000455349 0.000285211 -0.00127505]
principal moments: [0.0055373 0.0160106 0.0186473]
CoM: [-0.0066768 -0.00711079 0.227182 0 0 0]

Note that the optimized mesh has larger volume due to convex decomposition which leads to larger mass.

Here are the results with a fixed mass of: 1.50252

Before (no convex decomposition):

mass: 1.50252 
xx yy zz: [0.0133113 0.0115766 0.00378028]
xy xz yz: [0.000303647 0.000341477 -0.000880731]
principal moments: [0.00366758 0.0116338 0.0133668]
CoM: [-0.00637488 -0.00799589 0.132544 0 0 0]

After:

mass: 1.50252 
xx yy zz: [0.0132101 0.0114322 0.00408824]
xy xz yz: [0.00034167 0.000419915 -0.000875292]
principal moments: [0.00396275 0.011487 0.0132808]
CoM: [-0.0069944 -0.00689877 0.131142 0 0 0]

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[scpeters]

I'd be curious to compare the change in inertial properties before and after this PR when a fixed mass is specified

[iche033]

updated the description with inertial results from using a fixed mass. The difference is small.

[codecov]

Codecov Report

Attention: Patch coverage is 72.00000% with 7 lines in your changes missing coverage. Please review.

Please upload report for BASE (gz-sim9@54830b9). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/MeshInertiaCalculator.cc	72.00%	7 Missing ⚠️

Additional details and impacted files

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