[vtkusers] How to use the method "vtkCellLocator::IntersectWithLine()" ?

[Chavdar Papazov]

Hi Luca,

thanks for the reply. I've tried the method and it works fine.

But the problem is, that there is not just one intersection between a line and a vtkPolyData object. For example if we have a poly-sphere and a line, there could be two intersection points between the sphere and the line. And this method gives me only one point. It saves its coordinates in the "pline" argument (see below).
But how should I get all the intersection points?

Thanks!


Che


Luca Pallozzi Lavorante <lplavorante at gmail.com> wrote: Hi Che, 
 I have succesfully used vtkCellLocator::IntersectWithLine, although I don´t know the meaning of all its arguments:
 I have done the following:
 
 if (locator->IntersectWithLine(p1, p2, 0.001, t, pline, pcoords, subId, cellid, cell) != 0) {
   // Enters here if there is intersection
}
 
 where:
 
   p1 and p2 are the intersecting line´s endpoints,
   double t = 0.0;
   double pline[3] = { 0, 0, 0};
   double pcoords[3] = { 0, 0, 0};
    int subId = 0;
    int cellid = -1;
    vtkGenericCell *cell = vtkGenericCell::New();
 
 Using the 'cell' instance you can get interesting informations about the triangle involved in the intersection, but I haven´t  used this feature. 
 
 Also, don´t forget to do sometthing like this before invoking the IntersectWithLine method:
 
 vtkCellLocator *locator = vtkCellLocator::New();
    locator->SetDataSet(vtkPolyData* data);
    locator->BuildLocator();
 
 Hope this help
 
     Luca
 
 
On 11/20/06, Chavdar Papazov <chenkaz at yahoo.com> wrote: Dear VTK Users,

would you explain to me how to use the method 'IntersectWithLine()' of the class vtkCellLocator.
There are three versions of this method. The first one is:

virtual vtkCellLocator::IntersectWithLine(double a0[3],  
                                                          double a1[3],
                                                          double toi,
                                                          double& t,
                                                          double x[3],
                                                          double pcoords[3],
                                                          int& subid)


In the html-doc there is no explanation of the parameters of the method, so I don't know how to call it.
I have a vtkPolyData object and two points in 3D which define the line. And I want to check whether the line intersects the vtkPolyData object.

Do you have any ideas?
Thanks!

Che
   
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