Re: Point in Triangle

• To: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
• Subject: Re: Point in Triangle
• From: Desiree Hilbring <hilbring@xxxxxxxxxxxxxxxxxxxx>
• Date: Thu, 22 Feb 2001 17:32:01 +0100 (MET)

Hi Steve,
thanks for your immediate answer.
Unfortunately I am not familiar to Delaunay Triangulation.
Ok, I understand the Delaunay Triangulation breaks up my set of points in
a structure with triangles. I thinks this happens somewhere in Irregular2D
set. But how are the triangles organized?
What is the method getNeighbours doing? 
I am putting an 2D-array of floats in the the Irregular2D set, what is the
int[][] array in get Neighbours? Does it somehow specify the indices,
which floats cooresponds to an triangle?
Where can I find more Information about Irregular2D set?

Thanks again for your help

Desiree

o------------------------------------------------------------------------o
| Desiree Hilbring      Institut fuer Photogrammetrie und Fernerkundung  | 
|                       Universitaet Karlsruhe, Germany                  |
|                                                                        |
|                       email: hilbring@xxxxxxxxxxxxxxxxxxxx             |
|                       # 0721 6083676                                   |
o------------------------------------------------------------------------o

On Thu, 22 Feb 2001, Steve Emmerson wrote:

> Desiree,
> 
> Your question is really one for Bill Hibbard, the developer of VisAD.
> Unfortunately, he's travelling, so the rest of us will try to help.
> 
> Unfortunately again, I'm not familiar with triangulation algorithms
> (though I am familiar with VisAD).  If I had to guess, I'd suggest
> that you create the Irregular2DSet with a Delaunay triagulation that
> you explicitly obtain from the Delaunay.factory(...) method.  You
> should then be able to use the fields in the triagulation (Edges,
> Tri, Vertices, etc.) to discover in which triangle a point resides
> (assuming you're familiar with Delaunay triagulation).        For help on
> this, you might want to look at the getNeighbors(...) method in class
> IrregularSet.
> 
> Hope this helps.
> 
> Regards,
> Steve Emmerson   <http://www.unidata.ucar.edu>
> 
> >Date: Thu, 22 Feb 2001 16:16:54 +0100 (MET)
> >From: Desiree Hilbring <hilbring@xxxxxxxxxxxxxxxxxxxx>
> >Organization: UCAR/Unidata
> >To: visad-list@xxxxxxxxxxxxx
> >Subject: Point in Triangle
> >Keywords: 200102221519.f1MFJML15618
> >
> > Hi,
> > 
> > I have a given set of 3D-point and the x,y-coordinates of one point
> > somewhere in my set of points. I
> > want to interpolate the height of the point. 
> > I want to add this point in my set and use the Delaunay-Triangulation of
> > VisAD. 
> > Without this extra point the Delaunay Triangulation is working fine.
> > 
> > RealType x = RealType.getRealType("x");
> >     RealType y = RealType.getRealType("y");
> >     RealType height = RealType.getRealType("height");
> >     try {
> >         RealTupleType xy = new RealTupleType(x, y);
> >         FunctionType terrain_type = new FunctionType(xy, height);
> >         Irregular2DSet set = new Irregular2DSet(xy,new float[][]
> > {eastValues,northValues});
> >         FlatField terrain = new FlatField(terrain_type, set);
> >         terrain.setSamples(new float[][] {heightValues});
> >                 
> >         display = new DisplayImplJ3D("display1");
> >         ScalarMap hoxmap = new ScalarMap(x, Display.XAxis);
> >         ScalarMap reymap = new ScalarMap(y, Display.YAxis);
> >         ScalarMap heightmap = new ScalarMap(height, Display.ZAxis);
> >                 
> >         display.addMap(hoxmap);
> >         display.addMap(reymap);
> >         display.addMap(heightmap);
> >             
> >         hoxmap.setRange(-1.0, 1.0);
> >         reymap.setRange(-1.0, 1.0);
> >         heightmap.setRange(-1.0, 1.0);
> >         
> >         DataReferenceImpl data_ref = new
> > DataReferenceImpl("data_ref"); 
> >         data_ref.setData( terrain );
> >         renderer = new DefaultRendererJ3D();
> >         display.addReferences(renderer,data_ref);
> >         display.addDisplayListener(listener);
> >     }
> >     catch (VisADException ve) {
> >         System.out.println("VisAd TupleType Exception");
> >     }       
> >     catch (RemoteException re) {
> >         System.out.println("RemoteExcpetion");
> >     }
> > 
> > How can I find the triangle in which the point belongs to?
> > Are there some standard geometric algorithms to achieve that?
> > Where do I have to look at.
> > 
> > Thanks for your help in advance
> > 
> > Desiree
> > 
> > 
> > 
> > o------------------------------------------------------------------------o
> > | Desiree Hilbring  Institut fuer Photogrammetrie und Fernerkundung  | 
> > |                   Universitaet Karlsruhe, Germany                  |
> > |                                                                        |
> > |                   email: hilbring@xxxxxxxxxxxxxxxxxxxx             |
> > |                           # 0721 6083676                                  
> >  |
> > o------------------------------------------------------------------------o
> 

• References:
  • Re: Point in Triangle
    • From: Steve Emmerson