[vtkusers] 3D Visualization of Map Data

[Malcolm Drummond]

Hi Ron

You want to sample values from your terrain to points in your Shapefile data - this can't be done directly as they don't coincide in 3D. My approach is to store the terrain elevation data as scalars (via vtkElevationFilter) before flattening the terrain to coincide with the Shapefile data. At that stage you can probe one with the other. Then you map the probed scalar values back to the z component (via vtkWarpScalars).

The input to your  vtkTransformPolyDataFilter should be the output from the elevation filter i.e. ...

transFilter->SetInput(Elevation->GetOutput());

... this is to get your mesh into the same plane (z = 0.0) as your shapefile output. If they don't coincide then the probing will produce no data.

I'd take this in stages - much easier to do with Python or TCL scripting. First visualize the output of the transform filter and check that it is flat and that the elevation data is showing as scalars. Then add the shapefile to the visualization and check that they coincide (I just assumed that it was at z = 0.0, maybe not). Then add the probe filter and check that the probing works (i.e the output has interpolated scalar values). Finally add the warpscalars to get your elevation back.  

HTH
Malcolm Drummond

  ----- Original Message ----- 
  From: Ron Chapman 
  To: vtkusers at vtk.org 
  Sent: Wednesday, February 15, 2006 6:28 AM
  Subject: [vtkusers] 3D Visualization of Map Data


  Malcolm,

  I'm having problems trying to implement your suggestion.  

  >>One approach would be to run an elevation filter on your 3D map (to create scalar values) and then a >>transform with scale set to 1.0,1.0,0.0 which will set all your z values to 0.0. Then probe this dataset >>with your overlay features (which are at elevation 0.0) and run the output through vtkWarpScalars (to >>apply the sampled elevations to your overlay). The only problem is that sampling will only take place at >>points defined in your overlay dataset and the result may not look good due to non-sampled >>intersections with your 3D map. Adding some extra elevation to your overlay may fix this.


  I do understand that reconfiguring my 2D shape file to have points located on the edges of my 3d mesh is the best approach, and will attempt this once I get the above working first.

  Here is my pipeline

  ....

  // run the elevation filter to get the elevation scalars

   vtkElevationFilter *Elevation = vtkElevationFilter::New();
   Elevation->SetInput(Mesh3D);
   
   // convert our 3d mesh to 2d

   vtkTransform *Transform = vtkTransform::New();
   Transform->Scale(1.0,1.0,0.0);

   vtkTransformPolyDataFilter *transFilter = vtkTransformPolyDataFilter::New();
   transFilter->SetInput(Mesh);
   transFilter->SetTransform(Transform);


   // probe 2d mesh with shape data

      vtkProbeFilter *Probe = vtkProbeFilter::New();
     Probe->SetInput(Shape2D);
     Probe->SetSource(trasnFilter->GetOutput());
     
   // apply the sampled elevation to the overlay

   vtkWarpScalar *Warp = vtkWarpScalar::New();
   Warp->SetInput(Probe->GetPolyDataOutput());
   Warp->XYPlaneOn();

  ....

  I'm confused as to how the elevation filter and warpscalars are working together to get my 2D shape file into 3D?  The above pipeline is giving me garbage.

  Ron



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