| Re: access to vercities & connectivity data [message #36981 is a reply to message #36972] |
Mon, 10 November 2003 14:33  |
Rick Towler
Messages: 821
Registered: August 1998
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Senior Member |
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"Neil" wrote...
> I would like to read in a DXF file and get access to the numerical
> values of the vertices and the connectivity. That's all i wish to do,
> which IDL routines should i use for this task. From the IDL help it is
> not immediately obvious how this can be done.
There are a couple of ways:
You can use the IDLffDXF object. There is an example close to what you are
looking for in in the docs under IDLffDXF::Read. Also of interest will be
IDLffDXF::GetEntity which describes how to pull out the different entity
types. The types are described in the IDLffDXF::GetContents docs.
Another way, which is a bit of a hack but might be easier (especially if you
don't know what is in your DXF file) is to use the undocumented
GET_DXF_OBJECTS function (found in $RSI_DIR/lib/utilities). There is some
documentation in the file header.
Yet another way, which I had completely forgot about, is to use my dxfmodel
object which reads a dxf file (only extracts types 4,8,9, and 11) and
creates a model containing the primitives. It also gives you access to the
primitive objects (IDLgrPolyline and IDLgrPolygon) from which you could get
at the vertex and connectivity data. It requires David Fanning's linkedlist
object (linkedlist__define.pro) available from
http://www.dfanning.com/documents/programs.html
Using my dxfmodel object would go something like:
IDL> dxfmod=OBJ_NEW('dxfmodel', 'stonehenge.dxf')
% Loaded DLM: DXF.
IDL> p=dxfmod->getprimitive(0)
IDL> help, p, /struct
** Structure <1760450>, 4 tags, length=32, data length=30, refs=2:
BLOCK STRING ''
LAYER STRING 'biglent02'
TYPE INT 9
OBJECT OBJREF <ObjHeapVar252(IDLGRPOLYGON)>
IDL> p.object->getproperty, data=verts, polygons=conn
IDL> help,verts
VERTS DOUBLE = Array[3, 216]
IDL> help, conn
CONN LONG = Array[1200]
Note that dxfmodel__define isn't "finished" but unless you are in need of
extracting some odd dxf types it should work fine for what you want to do.
you can find my object here:
http://www.acoustics.washington.edu/~towler/dxfmodel__define .pro
Enjoy!
-Rick
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