Arrow heads freaking out occasionally

[AntonOresten]

Computing tangents/normals/binormals of the arrow surface is currently a little bit of a shitshow, which leads to issues like the one below.

I suspect it has to do with the spline (created from oxygen atoms) extending beyond the endpoint.

[AntonOresten]

This issue is getting fixed in v0.2.0 by removing the next to last control point (oxygen atom) of the two splines that form the surface and normals of a strand.

I also made it so that the angle between the arrow body and head is always 90 degrees -- it could look kinda funky when the spline quality was low.

This:

turned into this: (no wonky tips)

which in turn turned into this: (perpendicular edges)

As a result, the colors are also much more consistent.