Hello Firas,
indeed vmtkbranchextractor changes the dataset (it generates more lines), so
the order with which points appear changes. Same thing for
vmtkcenterlinesections.
If you want to combine point arrays you could use vmtksurfaceprojection, which
will
project scalar values from one surface (in a broad sense - also a centerline is
a surface
made of 1D cells) to another.
However, this will only project point data, such as radius, and not cell data,
such as
groupid. To do that, you first need to convert point data to cell data using
vmtksurfacecelldatatopointdata, but your mileage might vary, depending on what
you
want to integrate.
In general, though, if you really need to integrate for your own specific
needs, I can show
you how to do it using Python code. That way you're not stuck with how things
have been
pre-packaged. It's really hard to envision any possible combination.
Let me know what exact quantities you'd like to have and on what dataset, and I
can
think of practical suggestions to get there. Eventually, if something general
enough
comes out of this, we'll include it in vmtk.
As a starting point, look at vtkvmtkPolyBallLine (in
vtkVmtk/ComputationalGeometry). With
this class you can do
polyBallLine = vtkvmtk.vtkvmtkPolyBallLine()
polyBallLine.SetInput(centerlines)
polyBallLine.SetPolyBallRadiusArrayName('MaximumInscribedSphereRadius')
polyBallLine.UseRadiusInformationOn()
With this object, having the coordinates of a point, you can find out the cell,
subId (the id
of the point along the line) and pcoord (the normalized parametric coordinate
along the
segment from subId to subId+1) on the centelrine that is closest to the point
provided.
So, for example
point = [1.0,1.0,1.0]
polyBallLine.EvaluateFunction(point)
cellId = polyBallLine.GetLastPolyBallCellId()
subId = polyBallLine.GetLastPolyBallCellSubId()
pcoord = polyBallLine.GetLastPolyBallCellPCoord()
# now get the cell from the input dataset
cell = centerlines.GetCell(cellId)
# so you can get the pointId
pointId = cell.GetPointId(subId)
(see the code in vtkVmtk/vtkvmtkPolyDataCenterlineProjection.cxx as an example
in C++)
At this point, you have both the cellId and the pointId of the point on the
centerline that is
closest to your input point (which could be a point belonging to the centerline
where you
want to project your data onto). Using cellId and pointId, you can access both
point data
and cell data to get the quantities from one dataset to the other.
I hope I'm pointing you in the right direction. As I mentioned, if you provide
me with more
detail on the specific quantities you need and on what dataset you want them, I
can be more
specific.
Best regards
Luca
On Nov 21, 2010, at 5:22 PM, Firas Mualla wrote:
> Hi Luca,
>
> We get usefule vessel features from several vmtk scripts, and it would
> be nice if we can combine them. In principle, it is always possible to
> do the combination if we have the same geometry (points), because then
> we can iterate over the points array, and for each point, we get the
> features from (e.g. vmtkcenterlinegeometry, vmtkbranchextractor, and
> say vmtkcenterlinesections). If we have the same centerline input for
> the previous three scripts, we can for example get at each point the
> curvature, the torsion, the centerlineId, the groupId, the area of the
> inter-sections...etc.
>
> I've checked the outputs of the previous three scripts, and noticed
> that vmtkcenterlinegeometry has the same points array of the input, on
> the otherhand vmtkbranchextractor gives different points array (at
> least the order is different). vmtkcenterlinesections contains the
> sections points, and as I think each section is belonged to a cell. Is
> there a way in vmtk to do this combination?
>
> many thanks Luca in advance
>
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