Registration with ITK and a MicroScribe Digitizer

[Dirk Hollstein]

Hello,

we want to register data acquired from a microscribe digitizer with
data from an stl-file (stereo-lithography). We collect data by
sampling surface points on a real world object with the digitizer.
The stl-file describes this real world object (a cuboid).

We did look at the examples for PointSetToImageRegistrationTest_1 and
ModelToImageRegistration2, still we have several problems we could
not solve:

- How can we extract the necessary PointSet data from the stl-file
for registration (assuming PointSet is the way to go)? Currently we
read the stl-file with VTK.

- How can we get this data into ITK for registration?

- Do we have to process the stl file before we are able to register
it, e.g. by applying a certain filter to it?

- Is there a way to read an STL-file directly into ITK?

Any help is appreciated, since we do not know how to proceed from here.

Thanks a lot in advance,
Dirk

[Luis Ibanez]

Hi Dirk,

That sounds like a very interesting problem.

Here are some comments:

1) Converting VTK point set to ITK Point Set:

Option A:

Once you read the STL file with VTK you can
write it down as a VTK file and read it with
the new class:

Insight/Code/Review
itkVTKPolyDataReader.h
itkVTKPolyDataReader.txx


Option B:

You can convert the VTK polydata into an ITK
point set by using the code in:

InsightApplications/Auxiliary/vtk
vtkPolyDataToITKMesh.cxx


2) You don't really need to preprocess the point
set before performing the registration,
unless you have so many points that it is
worth to subsample the point set. If you
have less than 20,000 points and a decent
computer, then you shouldn't need to subsample.

It is a matter of balancing computation time
and registration precision and stability.



3) Nope,
there is not a way of reading an STL file
directly into ITK.





Regards,


Luis



======================

Post by Dirk Hollstein
Hello,
we want to register data acquired from a microscribe digitizer with
data from an stl-file (stereo-lithography). We collect data by sampling
surface points on a real world object with the digitizer. The stl-file
describes this real world object (a cuboid).
We did look at the examples for PointSetToImageRegistrationTest_1 and
ModelToImageRegistration2, still we have several problems we could not
- How can we extract the necessary PointSet data from the stl-file for
registration (assuming PointSet is the way to go)? Currently we read
the stl-file with VTK.
- How can we get this data into ITK for registration?
- Do we have to process the stl file before we are able to register it,
e.g. by applying a certain filter to it?
- Is there a way to read an STL-file directly into ITK?
Any help is appreciated, since we do not know how to proceed from here.
Thanks a lot in advance,
Dirk
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