Add attribute to indicate if a mesh is a convex hull?

[Levi-Armstrong]

Would the maintainer be open to adding an an attribute to the mesh tag indicating if the mesh is a convex hull? The default would be false.

<mesh filename="" convex="true" />

[sloretz]

Hi @Levi-Armstrong, did you have a particular use-case? It might be a topic worth opening up on https://discourse.ros.org/c/robot-description-formats

[gavanderhoorn]

The use-case here is to utilise this information in planners / collision checkers that can enable certain optimisations when the meshes they are passed are convex. One example would be FCL, which has optimised implementations for convex-convex algorithms.

As this is a property of the mesh that is difficult/impossible to derive at runtime, adding an optional attribute to the mesh element seems like a straightforward way to encode it.

[Levi-Armstrong]

@sloretz As @gavanderhoorn mentioned this is the main factor. Most of the collision libraries use libccd to perform convex-convex collision checking and it also provides the minimum translation vector when in collision which would could be used by several optimization based motion planners.

[de-vri-es]

Hi @Levi-Armstrong, did you have a particular use-case? It might be a topic worth opening up on https://discourse.ros.org/c/robot-description-formats

Thread on discourse: https://discourse.ros.org/t/add-attribute-to-indicate-if-a-mesh-is-a-convex-hull/4479

[briansoe66]

@Levi-Armstrong Although Tesseract URDF Package defines a urdf version 2 with extra elements, including a <convex_mesh>, this new urdf version does not seem to be very popular, because i cannot find many urdf 2 examples for popular robots. I prefer that urdfdom adds a attribute like you suggested.

https://ros-industrial-tesseract.readthedocs.io/en/stable/_source/tesseract_urdf_doc.html

[Levi-Armstrong]

The reason you probably do not find any reference is because the default behavior of tesseract is to convert all meshes to convex hulls.