Re: [Pythoncad-developer] PythonCAD elements and the xml schema.

[<mat...@bo...>]

Hi Gertwin,

We can create object structure starting from an xsd schema.

I .net i strongly use serialization, and I use to load very
huge xml file and this file will be loaded in a very short
time ..

In this link there is a proget that create some classes
starting from xml schema:
http://www.rexx.com/~dkuhlman/generateDS.html
I know that in python thare is the abiliti to load and write
object directly from file.

I don't whant to use the oracle db (It's not open source).

In the following days i will do some test and let you know
if we can do some improvments in this direction.

Regards,
Matteo
----- Original Message -----
Da : Gertwin Groen <ger...@gm...>
A : pythoncad-developer
<Pyt...@li...>,  Matteo Boscolo
<mat...@bo...>, Yagnesh Desai
<yn...@ln...>
Oggetto : PythonCAD elements and the xml schema.
Data : Wed, 13 Jan 2010 22:55:35 +0100

> Hello all,
> 
> I want to define a list of elements (entities) and their
> geometry primitives we want to provide in PythonCAD that
> are not yet supported. The file format of PythonCAD is
> described in the pythoncad.xsd schema, this the base of
> what a PythonCAD drawing can contain.
> 
> I think it is time to review this schema because it has an
> influence on everything we want to do with PythonCAD.
> This is very necessary because changes in the
> schema/drawing format are time consuming to implement in
> PythonCAD.
> 
> What we have:
> Current supported list of elements (from the pythoncad.xsd
> schema): - Points
> - Segments
> - Circles
> - Arcs
> - HCLines
> - VCLines
> - ACLines
> - CLines
> - CCircles
> - LDims
> - HDims
> - VDims
> - RDims
> - ADims
> 
> In PythonCAD there are more elements which are not
> described in the schema:
> 
> - TextBlock
> - Polyline
> - Fillets?
> - Chamfer?
> 
> What we want:
> Current unsupported list of elements/entities:
> - polylines with arcs
> - block definition and reference
> - ellipse arc
> - ellipse
> - hatch
> - polygon (as AutoCAD MPolygon, very similar to hatch)
> - ...
> 
> In the current schema all the elements are described and
> each of them has his own description of its geometry.
> If you give the schema a second look you see that multiple
> elements have a similar  geometric primitive.
> For instance:
> A segment is a polyline with 2 points.
> A circle is a arc with the start angle == end angle
> etc.
> 
> It would be better to have one geometric primitive where
> all the entities make use of it (if possible).
> Future elements can also make use of this geometric
> primitive or a group of primitives.
> If we have only one geometric datatype the drawing of the
> entities is much simpler (to maintain and for new
> elements).
> 
> Maybe a candidate for a geometric datatype is the oracle
> SDO_GEOMETRY datatype (I have a GIS background thats why I
> chose this). The only thing that is not directly supported
> is a ellipse.
> 
> The supported geometric types by the SDO_GEOMETRY datatype
> are (from the oracle documentation):
> 
> POINT
> Geometry contains one point.
> * PythonCAD element Point
> 
> LINE or CURVE
> Geometry contains one line string that can contain
> straight or circular arc segments, or both. (LINE and
> CURVE are synonymous in this context.)
> * PythonCAD element Segment, Polyline (with and without
> arcs)
> 
> POLYGON
> Geometry contains one polygon with or without holes.
> * PythonCAD element Hatch and Polygon
> 
> COLLECTION
> Geometry is a heterogeneous collection of elements.
> COLLECTION is a superset that includes all other types.
> 
> MULTIPOINT
> Geometry has one or more points. (MULTIPOINT is a superset
> of POINT.)
> 
> MULTILINE or MULTICURVE
> Geometry has one or more line strings. (MULTILINE and
> MULTICURVE are synonymous in this context, and each is a
> superset of both LINE and CURVE.)
> * PythonCAD element ellipse can be presented as a
> collection of arcs
> 
> MULTIPOLYGON
> Geometry can have multiple, disjoint polygons (more than
> one exterior boundary). (MULTIPOLYGON is a superset of
> POLYGON.) * PythonCAD element Hatch and Polygon
> 
> I think this datatype is not suited for describing 3D
> elements but I have no/very limited knowledge of 3D
> 
> Any thoughts on this?
> Better, other ideas?
> 
> Regards,
> Gertwin