Check normal presence before trying to read asMesh normals

[qingyouzhao]

🦟 Bug fix

Fixes there isn't a bug number

Summary

An assimp mesh could contain either

• the same number of vertices and normals
• only vertices

Existing code crashes when a mesh contains no normals

Checklist

• Signed all commits for DCO
• Added tests
• 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

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[azeey]

LGTM!

[azeey]

I'm not sure if the rest of Gazebo handles the case where there are no normals properly. @iche033 do you know?

[iche033]

I'm not sure if the rest of Gazebo handles the case where there are no normals properly. @iche033 do you know?

gz-rendering should be able to handle meshes without normals

However, I see that gz-physics' dartsim plugin requires normals to be present.

To be safe I think we should add a check and auto generate normals if the assimp mesh does not contain normals, i.e. in the same function before return subMesh; we can add something like:

if (subMesh.NormalCount() == 0u)
  subMesh.RecalculateNormals();

[qingyouzhao]

I'm not sure if the rest of Gazebo handles the case where there are no normals properly. @iche033 do you know?

gz-rendering should be able to handle meshes without normals

However, I see that gz-physics' dartsim plugin requires normals to be present.

To be safe I think we should add a check and auto generate normals if the assimp mesh does not contain normals, i.e. in the same function before return subMesh; we can add something like:

if (subMesh.NormalCount() == 0u)
  subMesh.RecalculateNormals();

@iche033 Added.

[iche033]

@Mergifyio backport gz-common5 gz-common6

[mergify]

backport gz-common5 gz-common6

✅ Backports have been created

• #656 Check normal presence before trying to read asMesh normals (backport #654) has been created for branch gz-common5
• #657 Check normal presence before trying to read asMesh normals (backport #654) has been created for branch gz-common6