[vtkusers] Interpolating point on a surface

[Bill Lorensen]

It doesn't have to be. I was commenting that your example created an
image that does require uniform sampling. Also, probing surfaces like
triangles is tricky. Probing is better suited to volumes. I think the
best solution to Ken's problem is to use CellLocator.

Bill

On Thu, Jan 21, 2010 at 2:21 PM, David Doria <daviddoria+vtk at gmail.com> wrote:
> On Thu, Jan 21, 2010 at 2:13 PM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
>>
>> Ken,
>>
>> I enhanced David D's example:
>> http://www.vtk.org/Wiki/VTK/Examples/InterpolateTerrain
>> to use the vtkCellLocator as well as the vtkProbeFilter. If your data
>> is uniformly spaced in a grid, then the ProbeFilter is appropriate. If
>> it is not uniform in x,y, then the CellLocator is what you want.
>>
>> Bill
>>
>> On Thu, Jan 21, 2010 at 11:13 AM, Bill Lorensen <bill.lorensen at gmail.com>
>> wrote:
>> > Ken,
>> >
>> > I think you want:
>> > Filtering/vtkCellLocator. It has a method:
>> >  // Description:
>> >  // Return intersection point (if any) AND the cell which was
>> > intersected by
>> >  // the finite line. The cell is returned as a cell id and as a generic
>> > cell.
>> >  // For other IntersectWithLine signatures, see vtkAbstractCellLocator
>> >  virtual int IntersectWithLine(double a0[3], double a1[3], double tol,
>> >                                double& t, double x[3], double
>> > pcoords[3],
>> >                                int &subId, vtkIdType &cellId,
>> >                                vtkGenericCell *cell);
>> >
>> > Just specify a large positive and negative Z for your lines.
>> >
>> > BTW, the sample looks like a golf green It it is, you may enjoy this
>> > paper I wrote with a colleague in 1992.
>> >
>> > Lorensen, W. E. and B. Yamrom, Golf Green Visualization, IEEE Computer
>> > Graphics and Applications, vol. 12, no. 4, pp. 35-44, 1992.
>> > http://marchingcubes.org/images/6/6f/GolfGreenVisualization.pdf
>> >
>> > Bill
>> >
>> > On Tue, Jan 19, 2010 at 7:02 PM, Kenneth Porter <shiva at sewingwitch.com>
>> > wrote:
>> >> --On Tuesday, January 19, 2010 1:21 AM -0500 Darshan Pai
>> >> <darshanpai at gmail.com> wrote:
>> >>
>> >>> I am not exactly sure what you are asking .
>> >>> maybe you can try the FindPoint() function in vtkPolyData....
>> >>
>> >> Imagine that I'm given a topo map and know latitude and longitude, and
>> >> need
>> >> to calculate the altitude.
>> >>
>> >> It looks like FindCell might do what I need:
>> >>
>> >>
>> >> <http://www.vtk.org/doc/nightly/html/classvtkDataSet.html#a2221c10d3c4cca44e82c5ef70e4e1cbd>
>> >>
>> >> I need to find the triangle that contains an X/Y point, where the Z is
>> >> unknown, so that I can compute the Z.
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>>
>
> Why does the data have to be uniformly spaced on a grid for the
> vtkProbeFilter? The documentation
> (http://www.vtk.org/doc/nightly/html/classvtkProbeFilter.html#_details)
> says
> "For example, an unstructured grid (vtkUnstructuredGrid) can be probed with
> a volume (three-dimensionalvtkImageData)"
> Thanks,
>
> David
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