Fixed bug related to cutoff array

The cutoff array should be defined in the input point data, not in
in the source point data.

Filters/Points/Testing/Python/TestSPHInterpolatorWithCutoff.py

@@ -32,12 +32,8 @@ output = reader.GetOutput()
 scalarRange = output.GetPointData().GetArray("Rho").GetRange()
 
 output2 = dsa.WrapDataObject(output)
-# the constant value in the Cutoff array below is equal to
-# the spatialStep (0.1) set below, and the CutoffFactor (3) of the QuinticKernel
-Cutoff = np.ones(output.GetNumberOfPoints()) * 3.0/10.0;
 Mass = np.ones(output.GetNumberOfPoints()) * 1.0;
 output2.PointData.append(Mass, "Mass")
-output2.PointData.append(Cutoff, "Cutoff")
 
 # Something to sample with
 center = output.GetCenter()
@@ -53,6 +49,15 @@ plane.SetCenter(center)
 plane.SetNormal(0,0,1)
 plane.Push(1.15)
 plane.Update()
+planeOutput = plane.GetOutput()
+planeOutput2 = dsa.WrapDataObject(planeOutput)
+
+# The constant value in the Cutoff array below is equal to
+# the spatialStep (0.1) set below, and the CutoffFactor (3) of the QuinticKernel.
+# Note that the cutoff array should be associated with the input
+# sampling points.
+Cutoff = np.ones(planeOutput.GetNumberOfPoints()) * 3.0/10.0;
+planeOutput2.PointData.append(Cutoff, "Cutoff")
 
 # SPH kernel------------------------------------------------
 

Filters/Points/vtkSPHInterpolator.cxx

@@ -325,6 +325,7 @@ void vtkSPHInterpolator::Probe(vtkDataSet* input, vtkDataSet* source, vtkDataSet
 
   // Set up the interpolation process
   vtkIdType numPts = input->GetNumberOfPoints();
+  vtkPointData* inputPD = input->GetPointData();
   vtkPointData* sourcePD = source->GetPointData();
   vtkPointData* outPD = output->GetPointData();
 
@@ -359,7 +360,7 @@ void vtkSPHInterpolator::Probe(vtkDataSet* input, vtkDataSet* source, vtkDataSet
   // Initialize the SPH kernel
   if (this->Kernel->GetRequiresInitialization())
   {
-    this->Kernel->SetCutoffArray(sourcePD->GetArray(this->CutoffArrayName));
+    this->Kernel->SetCutoffArray(inputPD->GetArray(this->CutoffArrayName));
     this->Kernel->SetDensityArray(sourcePD->GetArray(this->DensityArrayName));
     this->Kernel->SetMassArray(sourcePD->GetArray(this->MassArrayName));
     this->Kernel->Initialize(this->Locator, source, sourcePD);

Filters/Points/vtkSPHInterpolator.h

@@ -31,11 +31,11 @@
  * name of the source's density and mass arrays can optionally be provided;
  * however if not provided then the local volume is computed from the
  * kernel's spatial step. Finally, a cutoff distance array can optionally be
- * provided when the local neighborhood around each point varies. The cutoff
- * distance defines a local neighborhood in which the points in that
- * neighborhood are used to interpolate values. If not provided, then the
- * cutoff distance is computed from the spatial step size times the cutoff
- * factor (see vtkSPHKernel).
+ * provided (as part of the input P point data) when the local neighborhood
+ * around each sample point varies. The cutoff distance defines a local
+ * neighborhood in which the points in that neighborhood are used to
+ * interpolate values. If not provided, then the cutoff distance is computed
+ * from the spatial step size times the cutoff factor (see vtkSPHKernel).
  *
  * Other options to the filter include specifying which data attributes to
  * interpolate from the source. By default, all data attributes contained in