3D meshes for long extrusions are low quality

[amshahriar]

If we use gmsh to generate a mesh for an extruded circle, there's no way to enforce meshsized_entity in the third dimension. Therefore, for long extrusions, we run into awkwardly shaped meshes like this one.

[hughcars]

Recreated the issue in a toy, the size field is not being mapped along the sides in any extrusion.

Have a workaround to apply to surfaces manually selected, but this isn't ideal, as it will also fully mark the end plate of any extrusion, whereas really we only want along the outerwall ideally. This is because the both the outer and end surfaces are included the extrusion

[gpeairs]

I'm pretty sure this doesn't set a mesh size field on the boundary, which could be a problem, but it does at least mesh the extrusion nicely:

cs = CoordinateSystem("test")
place!(cs, Circle(5μm), :test)
sm = SolidModel("demo"; overwrite=true)
render!(sm, cs)
sm["extrusion"] =  SolidModels.extrude_z!(sm, "test", 50μm; num_elements=[10])

[hughcars]

num_elements works, but you can have a hard time reconciling it with an enclosing unstructured mesh, or even a number of surrounding extrudes lacking a common factor. I.e. if using num_elements, you need to use the same value on the enclosing substrate. This 10:3 combination for instance fails with

Error   : Could not find extruded vertex (0.1205366802553232, 0.992708874098054, 3.333333333333333)
Error   : Could not find extruded vertex (0.1205366802553232, 0.992708874098054, 3.333333333333333)
Error   : Could not find extruded vertex (0.1205366802553232, 0.992708874098054, 6.666666666666666)
Error   : Could not find extruded vertex (0.1205366802553232, 0.992708874098054, 6.666666666666666)

This might not be an issue though. Maybe we decide on the number of elements for a substrate extrusion based on the height, then can use the same on all extrusions over that thickness...?