Summary

Consider the following code:

set_3d_properties should be passed a verts argument, but is not passed that in the constructor.

It is not clear how to get rid of that.

A few points worth considering:

• PathPatch3D does take a path as the first argument. Doing something similar, i.e. have a verts instead of *args will break subclassing as done in e.g. [Bug]: unavoidable DeprecationWarning when using Patch3D #21740
• setting a default verts=None in set_3d_properties and then set it to get_verts may be a feasible solution, but will break as _path2s is not set here. For subclasses defining their own get_path or _path2d it would make sense though.
• It is possible to call set_3d_properties with an empty verts, but the only benefit is that _segment3d is set (to an empty list.

This seems to have been the case since the very first commit of mplot3d.

Proposed fix

I see a few possible solutions:

1. Dropping the __init__ method completely. A bit weird since one can pass zs and zdir to all other 3D methods.
2. Add a verts kw args so that one can construct the patch directly. This seems to not be the case for Patch though which must be subclassed(?).
3. Passing verts=self.get_verts() which will allow subclasses to work properly, but disallows instantiating a Patch3D directly.
4. 3 with a try-except for get_verts()

4 is probably the safest.