Extend set_offsets to 3D for Path3DCollection, Patch3DCollection

[scottshambaugh]

Summary

When creating 3D animations, it's best practice to update positions for the scatter points rather than re-drawing the whole thing. However, the only way to do this currently is to write to the private attribute _offsets3d directly. We should have a public set_offsets method to mirror the 2D behavior.

See also: https://stackoverflow.com/questions/41602588/how-to-create-3d-scatter-animations

Proposed fix

No response

[scottshambaugh]

Note to self, set_facecolor seems potentially messed up too.

Edit: this is a separate issue, see #27555

[timhoffm]

I imagine there will be quite a number of similar cases around.

This is a major downside of the concept to promote 2D to 3D by subclassing. One would have to make sure that all 2d API and logic is overwritten. But AFAICT this has not been done.

[scottshambaugh]

Yeah, agreed. It's a bit of a pain because it'll be a pretty big effort to go scrub everything - quite a few methods work just fine being subclassed. For right now I figure I can knock down things as they come up. Might be worth doing a look through the top mplot3d stackoverflow questions to see if there are any gaps identified there.

[scottshambaugh]

This is a partial duplicate of #784

[spinicist]

Hello, after spending all morning wondering why my 3D animation with set_offsets() wasn't working I finally found this issue. Hence I am a +1 for fixing this please!