performance of `mesh_import` can be improved

[jf---]

in compas the parsing of meshes is performed in compas python code, rather than via a dependency.
trimesh would be a solid contender since its easy to install and yields numpy arrays.
loading meshes could be about twice as fast (frankly, I expected an even greater contrast), but 2x is not to be sneezed at.

there are 2 possible routes:

1. make trimesh a hard dependency
2. make trimesh a soft dependency
3. factor out the existing mesh loading implementation and replace by trimesh calls

I strongly suggest making trimesh a hard dependency (updating requirements.txt) since once a dependency it is complimentary to compas.datastructures.Mesh. The soft route is using trimesh when found (as an alternative code path)

when going for the hard dependency I suggest refactoring mercilessly and factoring out the older implementations.

from line_profiler import profile

def test_mesh_read_performance_old():
    @profile
    def test_import():
        for i in range(10):
            msh: Mesh = Mesh.from_ply(compas.get_bunny())

            print(f"faces parsed {len(msh.facedata)}")
            del msh
    test_import()

def test_mesh_read_performance_trimesh():
    import trimesh
    @profile
    def test_import():
        for i in range(10):
            msh = trimesh.load(compas.get_bunny())

            print(f"faces parsed {len(msh.faces)}")
            del msh
    test_import()


def test_mesh_read_performance_meshio():
    import meshio
    @profile
    def test_import():
        for i in range(10):
            msh = meshio.read(compas.get_bunny())
            print(f"faces parsed {msh.cells_dict['triangle'].shape[0]}")
            del msh
    test_import()

---

test_robot_library.py::test_mesh_read_performance_old

============================== 1 passed in 4.17s ===============================
PASSED [100%]faces parsed 69451
faces parsed 69451
faces parsed 69451

test_robot_library.py::test_mesh_read_performance_trimesh

============================== 1 passed in 2.23s ===============================
PASSED [100%]faces parsed 69451
faces parsed 69451
faces parsed 69451

test_robot_library.py::test_mesh_read_performance_meshio

============================== 1 passed in 2.37s ===============================
PASSED [100%]faces parsed 69451
faces parsed 69451
faces parsed 69451

[tomvanmele]

hi @jf---

we can only start doing this in COMPAS 3, because of backward compatibility with older versions of Rhino.

development of C3 has stalled a bit, but i will restart it by opening a discussion and related development project where we can collect suggestion for the new API and new features...

[jf---]

@tomvanmele sounds like a plan (I'd love chip in wrt C3, I have some compas_fab specific ideas I'd love to run by you and @gonzalocasas ). Wrt triage, what about tagging issues that should surface when C3 is due?