Wasn't it Slime who wrote:
>> But "sphere {<5,5,5>,-7}" does have some really weird properties.
>
>
>Yeah, these are weird. In this case, then, it probably *does* make sense to
>either (a) make it behave as expected or (b) produce an error message.
>
>And probably b, since the "expected" behavior is probably hard to agree on.

I think an error is preferable, but one reasonable expected behaviour
would be to have it behave in the same way as a cylinder. A cylinder of
negative radius is indistinguishable from a cylinder of positive radius
in all respects that I've tested. This could easily be achieved by
taking the abs() of the radius as the sphere is parsed. 


We should also consider the sphere_sweep with negative radius which
exhibits most of the same weirdness as the sphere, and possibly the
torus with negative major radius which is weird in a different way.
The other primitive shapes seem to behave sensibly.

-- 
Mike Williams
Gentleman of Leisure

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