| Re: access to vercities & connectivity data [message #36972 is a reply to message #36962] |
Tue, 11 November 2003 13:12   |
nasalmon
Messages: 33
Registered: August 2003
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Member |
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"Rick Towler" <rtowler@u.washington.edu> wrote in message news:<bop3rj$20ts$1@nntp6.u.washington.edu>...
> "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
Thank you Rick for you comments. Well i decided on option 1 of yours
from above.
So i wrote this simple programme, trying to access the "verticies" and
"connectivity" from the DXF file in the examples from the heart file:
filename = filepath('heart.dxf', subdir=['examples', 'data'])
oTest = OBJ_NEW('IDLffDXF') ; Initialize DXF data access object
status = oTest -> Read(filename); Read data within DXF file into
access object.
TestTypes = oTest -> GetContents(COUNT = TestCounts);Determine what
type entity (and how many of each entity) exist in the file.
PRINT, 'Entity Types: ', TestTypes
PRINT, 'Count of Types: ', TestCounts
oModel = OBJ_NEW('IDLgrModel'); Initialize a model for displaying
tissue = oTest -> GetEntity(TestTypes[1]); Obtain the tissue data.
HELP, tissue
HELP, tissue, /STRUCTURE
print, 'vertices',tissue.vertices
print, 'connectivity',tissue.connectivity
This seems to be getting part of the way, the information looks the
right stuff, but i dont know if all the routine calls are necessary.
However, i do not yet seem to be able to access the real numberical
values of the "verticies" and "connectivities". I can see that
tissues.verticies and tissue.connectivity are pointers, but to what?
How do i get the one dimensional array with all the connectivity and
the 3 by n array of verticies? Which variable holds the data?
many thanks,
Neil
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