[PythonCAD] pythoncad drawing

Eric Wilhelm ewilhelm at sbcglobal.net
Tue Jul 27 17:35:07 CEST 2004


# The following was supposedly scribed by
# Art Haas
# on Tuesday 27 July 2004 09:44 am:

>> 4.  I find the point-table concept somewhat  objectionable.  Unless you
>> are aiming for relational drafting, it seems somewhat overkill.
>
> 
>???

If this is associative or relational drafting, then you have a circle with a 
center point, and a segment which uses that same point plus another point.  
If you move the circle, the segment moves.  If you move the segment, the 
circle moves.  (Actually, you are moving the point, which is being shared 
between entities.)  Is this a behavior you were aiming for?

I think it is mainly an issue about importing geometry.

Without digging into the code, I can offer this example:
 http://ericwilhelm.homeip.net/uber-converter/examples/dup_points.xml

pythoncad doesn't like loading this hand-modified file.  I'm guessing that it 
(the use of a point table) has something to do with your snap scheme.

dwg and dxf files are going to have points stored in each entity, even if they 
are matching points.  Because of round-off error, it seems that you would 
have an expensive point-comparison task to import a large dwg/dxf into 
pythoncad.

Also, what is the relationship between points on different layers?  If there 
can be duplicated points on separate layers, then you don't have the 
associativity between objects on different layers.  That seems somewhat 
inconsistent.  To be consistent, you would need a global points table instead 
of per-layer.

--Eric
-- 
"Blessed are the young, for they shall inherit the national debt."
                                        --Herbert Hoover


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