| Re: access to vercities & connectivity data [message #36962] |
Wed, 12 November 2003 10:01 |
Rick Towler
Messages: 821
Registered: August 1998
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Senior Member |
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"Neil" wrote...
> "Rick Towler" wrote ...
>> "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.
> Thank you Rick for you comments. Well i decided on option 1 of yours
> from above.
> 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?
Neil,
You are sooooo close. You probably have already figured this out but try:
print, *tissue.connectivity
print, *tissue.vertices
As you discovered, the GetEntity method returns a structure which contains 3
pointers. Without really getting into it, pointers in IDL are lightweight
tokens that "point to" some data. The pointer variable only contains a
reference to that data which is what you have discovered. What you need to
do is to dereference your pointer using the "*" character.
Pointers are persistent heap variables. That means that they will exist
until you explicitly destroy them or exit IDL. What may not be obvious is
that when using the IDLffDXF object the pointers that are returned to you
are your responsibility. You must keep track of them and free them using
PTR_FREE() when you are finished. Something as simple as the following
would work:
tissue = oTest -> GetEntity(TestTypes[1])
verts = *tissue.vertices
conn = *tissue.connectivity
PTR_FREE, [tissue.vertices, tissue.connectivity, $
tissue.vertex_colors]
-Rick
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| 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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| 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
|
Senior Member |
|
|
"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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