> On 09/04/2011 10:23 AM, Christian Froeschlin wrote:
>> Stephen wrote:
>>
>>>> Missusing union causes many "Sould have more than one
>>>> objects in CSG".
>>>
>>> Yes my constant companion. :-(
>>> But a necessary evil.
>>
>> You could suggest to the Bishop3D team that unions
>> with one element get exported as object instead.
>
> I obviously did not make myself clear. Putting a single object in a
> union is a workaround because Bishop3D does not have a local axis and if
> you want to rotate the object around a point, that is the only way to do
> it.
Not at all.
> If Bishop3D did as you suggest then it would break its import feature
> and import the object as fixed at the point of import.
>
> I did, of course, suggest to the development team that a local axis
> would be useful. That was some years ago.
>
>

POV-Ray also don't have "local" axis, only 1 set of global axis.

If the object is named, then there is NO need to use union.
Whenever you find yourself placing a single object in an union, use 
"object" instead.

If you want to place several objects around an axis at a given radius, 
then the way to do it is:

union{
  object{Object1 translate Radius rotate<x,y,z>}//Correct
  object{Object2 translate Radius rotate<x,y,z>}
...
rotate Global_Union_Rotation
translate Global_Object_Location
}

You wrongly suggers this:
union{
  union{Object1 translate Radius rotate<x,y,z>}//NOT correct
  union{Object2 translate Radius rotate<x,y,z>}
...
rotate Global_Union_Rotation
translate Global_Object_Location
}

Anyway, it's usualy beter to model all objects around the origin, scale 
and rotate them as needed, then to translate them to the desired location.
A lamp should reside with it's base at y=0.
A door with it's hinge at x=0, z=0.
A cabinet with it's back at x=0 or z=0.



Alain

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