Fw: [vtkusers] Help! How to slice a volume data arbitrary?

[Roland Schwarz]

----- Original Message -----
From: "Giancarlo Amati" <amati at ira.cnr.it>
To: "Roland Schwarz" <roland.schwarz at chello.at>
Sent: Thursday, April 04, 2002 10:43 AM
Subject: Re: [vtkusers] Help! How to slice a volume data arbitrary?


>
> Hi plato,
>
> try to use a combination between vktPlane that is a class that define the
> plane and a vtkCutter  (or vtkCutting I do not remember) which take in
> input the implicit function vtkPlane defined before and the input dataset,
> I found some example in the following site:
> http://www.rug.nl/hpc/VTK/vtk/man.html
>
> Best regards,
> Giancarlo Amati
>
>
> On Thu, 4 Apr 2002, Roland Schwarz wrote:
>
> > Hi Plato,
> >
> > I am not sure what you want, but cutting points in 3-d basically is a
> > dot-product of a plane vector with the respective point.
> > Say, you have a plane defined by its homogenous coordinates: (a,b,c,d)
then
> > have your point defined in its homeogenous coordinates (x,y,z,1).
> >
> > Then calculate d = a*x + b*y + c*z +d*1. If d > 0 the point is on one
side
> > of the plane, if not it is on the other.
> > Also have a look what is called (Hessesche-) Normal-Form of the plane
> > equation.
> >
> > Again I am not sure what you really need.
> >
> > Roland
> >
> >   ----- Original Message -----
> >   From: platogao
> >   To: vtkusers at public.kitware.com
> >   Sent: Thursday, April 04, 2002 9:14 AM
> >   Subject: [vtkusers] Help! How to slice a volume data arbitrary?
> >
> >
> >   Hi,
> >   I have a volume data set. I want to get the arbitrary slice of the
volume.
> > That is: you can define your our plane function to cut or slice the
volume,
> > and then get the slice image.
> >   I know this is very easy if use vtkCutter or vtkProbe or
vtkImageReslice.
> > But they are 'black box' to me. I cannot control every step of the
> > operation. I need to do this operation use C++ and OpenGL.
> >   My idea is that: use a point and a normal to define the plane. Then
> > convert every points in the plane(use 2d coordinate,say image[i,j]) to
3d
> > coordinate(x,y,z). Then see if (x,y,z) is in the volume. If it is in,
use
> > linear interplation to get the Value(x,y,z).
> >   My idea seems straight forword, but I think it is also very slow. I
wonder
> > if anyone can give me some advise on this operation, or how to convert
(i,j)
> > from a plane to world coordiante (x,y,z).
> >   Thank you very much!
> >   Plato Gao
> >
> >
> >
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> --
> ----------------------------------------
> dott. Giancarlo Amati                  |
> (amati at ira.cnr.it)                     |
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