[vtkusers] creating a solid object from 3D points

[Tim Hutton]

So there was a 3D image (CT I'm guessing) that has been contoured by
some program (probably at some iso-intensity), and you have the
vertices from that and you want to make a surface. If that is the
case, you *had* a surface and then threw it away, and now you want it
back. :)

The correct answer is: use the original 3D image to generate a
polygonal surface using a decent contouring algorithm.

The practical answer is: (since you probably no longer have the 3D
image) try powercrust. If it doesn't work then pester the people who
generated this data to give you the original 3D image.

(I'm amazed how often this comes up, there must be some badly
documented software out there.)

Hope this helps,

Tim

On 9/11/06, Clare Fitzpatrick <clare.fitzpatrick at ucd.ie> wrote:
> Hi Tim,
> Thanks for your reply.
>
> These points are points from the shaft of a bone. The points are captured as
> several 2D slices, each 2D slice taken at a different depth in the bone. The
> points at each depth could be rearranged into left-to-right, or ordered
> polar coordinate points, without too much trouble. I know it is possible to
> do it by creating polygons between adjacent slices, but I was hoping there
> might be a more efficent way. I tried using vtkSurfaceReconstructionFilter
> which seems to reconstruct the shape of the object, but has altered the
> scale and origin ...
>
> Clare
>
>
>
> ----- Original Message -----
> From: "Tim Hutton" <tim.hutton at gmail.com>
> To: "Clare Fitzpatrick" <clare.fitzpatrick at ucd.ie>
> Cc: <vtkusers at vtk.org>
> Sent: Monday, September 11, 2006 2:46 PM
> Subject: Re: [vtkusers] creating a solid object from 3D points
>
>
> > Hi Clare,
> >
> > First of all, are your points completely random or are they captured
> > in some direction, such as left-to-right? If so then you will probably
> > have more success using this fact to derive a surface. If your points
> > are geographical, for example, then a projection into 2D followed by
> > vtkDelaunay2D is the best option.
> >
> > If the points are definitely in a random order then you need some form
> > of surface reconstruction. VTK has vtkSurfaceReconstructionFilter but
> > it only works if your data is densely sampled all over, and the
> > surface is closed.
> >
> > A better algorithm is found in the following, which is written for VTK
> > but covered by the GPL:
> > http://www.sq3.org.uk/powercrust/
> >
> > Tim
> >
> > On 9/11/06, Clare Fitzpatrick <clare.fitzpatrick at ucd.ie> wrote:
> > >
> > >
> > > Hi,
> > >
> > > I have a set of x,y,z points which i want to convert to a solid object.
> > > I am reading them into vtk using vtkParticleReader:
> > >
> > > vtkParticleReader reader
> > >   reader SetFileName "C:/points3D.txt"
> > >   reader SetDataByteOrderToBigEndian
> > >
> > > vtkPolyDataMapper mapper
> > >     mapper SetInputConnection [reader GetOutputPort]
> > >
> > > vtkActor actor
> > >     actor SetMapper mapper
> > >     [actor GetProperty] SetPointSize 1
> > >
> > > ren1 AddActor actor
> > >
> > >
> > > The points in my .txt file are in a random order. Is it possible to
> create a
> > > solid object (the shape you'd get if you shrink-wrapped something around
> all
> > > the points) directly from these points, or do i have to arrange them
> into a
> > > particlar order so that i can use vtkDelaunay2D or vtkCellArray and
> > > vtkPolyData to create the surface?
> > >
> > > Thanks
> > >
> > > Clare
> > >
> > >
> > > _______________________________________________
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> > >
> > >
> > >
> >
> >
> > --
> > Tim Hutton - http://www.sq3.org.uk
> >
> > Take the Organic Builder challenge -
> > http://www.sq3.org.uk/Evolution/Squirm3/OrganicBuilder/
> >
>
>


-- 
Tim Hutton - http://www.sq3.org.uk

Take the Organic Builder challenge -
http://www.sq3.org.uk/Evolution/Squirm3/OrganicBuilder/