Rewrite put_start_and_end_on to work in 3D

[Darylgolden]

Changelog / Overview

Motivation

Previously,

class MovingVertices(ThreeDScene):
    def construct(self):
        self.set_camera_orientation(phi=75 * DEGREES, theta=30 * DEGREES)
        vertices = [1, 2, 3, 4]
        edges = [(1, 2), (2, 3), (3, 4), (1, 3), (1, 4)]
        g = Graph(vertices, edges)
        self.play(Create(g))
        self.wait()
        self.play(g[1].animate.move_to([1, 1, 1]),
                  g[2].animate.move_to([-1, 1, 2]),
                  g[3].animate.move_to([1, -1, -1]),
                  g[4].animate.move_to([-1, -1, 0]))
        self.wait()

broke and rendered like this:

scriptoutput.1.mp4

Rewriting put_start_and_end_on to work in 3D fixes this:

MovingVertices.mp4

the angle is slightly different? There seems to be non-deterministic output with that code. Stable also has that problem (at least on my system), so I don't think it's my fault.

Testing Status

Further Comments

Dependent on #1354. I hope I did the git stuff properly.

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[Darylgolden]

This branch has the same non-deterministic errors I pointed out on #1354. I'm also not sure what to do about the failing tests on Mac, it seems like numpy evaluates the function slightly differently on there, causing a very small numerical error.

[jsonvillanueva]

This branch has the same non-deterministic errors I pointed out on #1354. I'm also not sure what to do about the failing tests on Mac, it seems like numpy evaluates the function slightly differently on there, causing a very small numerical error.

Seems related to #972

[Darylgolden]

Even after rounding, the tests still fail on Mac because -0 is different from 0 for some reason.

[Darylgolden]

I managed to get the tests working, but using sort of hacky methods.

[Darylgolden]

I've written a test in three_d, let me know if it's misplaced.

[behackl]

LGTM! I only have one cosmetic remark (which doesn't really matter though); I think this can also be merged as-is.

[behackl]

I noticed that the test time went up by a bit, and after checking the test out locally I see that my suggestion was bad: Dot3D is rather heavy for the rendering (although it looks better in the example). I've reverted the test and the corresponding data back to using the default vertex type. If the pipeline passes after this, the PR can be merged.