Internal bottom chamfer threads don't render

[lincolnjohnson]

It seems that bottom_loop.intersect(chamfer_shape) creates a zero-volume object and is dropped as a result of the following volume check.

I've been unable to trace the root cause further.

bd_warehouse/src/bd_warehouse/thread.py

Line 214 in 67e697a

bottom_loop = bottom_loop.intersect(chamfer_shape)

[lincolnjohnson]

Possibly connected:

Internal threads made with a top chamfer have this interesting buckle shape on the third thread from the top. They appear to be located at +120° and +240° rotated around the Z axis, when X+ is considered as 0°.

[gumyr]

@lincolnjohnson, do you mind checking this again after my latest commit? I think everything is good now so hopefully this issue can be closed.