Add <voxel_resolution> SDF element to <convex_decomposition>

[iche033]

🎉 New feature

Summary

Adds a new <voxel_resolution> parameter. This is only applicable to voxel based convex decomposition methods.

See below for alternative proposals that I have considered. I'm open to suggestions.

Alternatives considered

1. Use a more generic parameter <resolution> instead of <voxel_resolution> so that it's applicable to a wider range of convex decomposition methods. e.g.

<convex_decomposition>
   <resolution>100000</resolution>
</convex_decomposition>

One example of non-voxel based method is the CoACD method which offers a couple resolution configuration params (resolution and manifold preprocess resolution).

2. Have specific SDF elements for each different method / library (similar to how there is <bullet>, <ode>, and <dart> specific params):

<convex_decomposition>
  <VHACD>
    <voxel_resolution>200000</voxel_resolution>
  <VHACD>
  <some_other_method>
    <another_param>50</another_param>
  <some_other_method>
</convex_decomposition>

This PR chose an approach that's kind of half way between the 2 above alternatives. I added the <voxel_resolution> SDF element to be more explicit in limiting this element to voxel based methods but not overly specific to a particular convex decomposition library.

One option for extending the spec in the future would be:

<!-- `method` can be VHACD, CoACD, etc and this determines the corresponding resolution param to use --> 
<convex_decomposition method="VHACD>
  <voxel_resolution>200000</voxel_resolution>
  <manifold_resolution>50</manifold_resolution>
</convex_decomposition>

Test it

Run the tests: UNIT_Mesh_TEST and INTEGRATION_geometry_dom

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)
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[scpeters]

what are the units of the voxel resolution parameter? is it a volumetric density or a number of elements?

[iche033]

updated description to say that resolution is the number of voxels. 5416ba5