Am 02.05.2016 um 14:57 schrieb William F Pokorny:

> The issue looks to be this code in the parser for the lathe object :

That is indeed the location in the code that rejects the negative value.

> Probably simple enough I could attempt a fix... Needs a conditional
> based on whether we have bezier curve I think. If someone else is going
> after a fix please speak up, otherwise I'll step up and try for one.

I would want more to be done than just address the symptoms (in this
case a negative control point value being rejected): First thing to be
done should be some thorough testing...

- whether the bezier-type lathe can actually deal with negative
off-curve control points (I expect it can, but that's not necessarily a
given);

- whether the bezier-type lathe can live with negative on-curve control
points (I wouldn't be too surprised if it actually can); and

- whether any of the other types of lathe can live with negative control
points (I would expect them to react the same as the bezier type does
with on-curve points, but that's not a given either).

Once that's established, the parser code should be adapted accordingly.

Also, if it turns out that the bezier-type lathe is fine with negative
off-curve control points but not on-curve control points, some thought
and possibly effort should be put into the case that some off-curve
points are so far in the negative regime that the resulting curve gets
pulled across the axis of revolution.


That's the reason why I'm not tackling this issue straight away myself.

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