ENH: Compute global AMR box w/prescribe spacing

Added functionality to compute the global AMR box,
i.e., an AMR box that covers the entire domain, with
the prescribed spacing.

Filtering/vtkHierarchicalBoxDataSet.cxx

@@ -483,6 +483,40 @@ void vtkHierarchicalBoxDataSet::GetRootAMRBox( vtkAMRBox &root )
   root.SetProcessId( -1 ); /* not owned, can be computed by any process */
 }
 
+//----------------------------------------------------------------------------
+void vtkHierarchicalBoxDataSet::GetGlobalAMRBoxWithSpacing(
+    vtkAMRBox &box, double h[3] )
+{
+  vtkAMRBox root;
+  this->GetRootAMRBox( root );
+
+  double min[3]; double max[3];
+  root.GetMinBounds( min );
+  root.GetMaxBounds( max );
+
+  int ndim[3];
+  ndim[0]=ndim[1]=ndim[2]=0;
+
+  for(int i=0; i < root.GetDimensionality(); ++i )
+    {
+      // Note -1 is subtracted here because the data
+      // is cell-centered and we downshift to number
+      // from 0.
+      ndim[ i ] = round( (max[i]-min[i])/h[i] )-1;
+    }
+
+  int lo[3];
+  lo[0]=lo[1]=lo[2]=0;
+
+  box.SetDimensionality( root.GetDimensionality() );
+  box.SetDataSetOrigin( min );
+  box.SetGridSpacing( h );
+  box.SetDimensions( lo, ndim );
+  box.SetLevel( 0 );
+  box.SetBlockId( 0 );
+  box.SetProcessId( -1 ); /* any process can compute this block */
+}
+
 //----------------------------------------------------------------------------
 int vtkHierarchicalBoxDataSet::GetMetaData(
     unsigned int level, unsigned int index, vtkAMRBox &box)

Filtering/vtkHierarchicalBoxDataSet.h

@@ -95,6 +95,11 @@ public:
   // The root AMR box covers the entire domain.
   void GetRootAMRBox( vtkAMRBox &root );
 
+  // Description:
+  // This method returns the global AMR box, covering the entire
+  // domain, with the prescribed spacing.
+  void GetGlobalAMRBoxWithSpacing( vtkAMRBox &box, double h[3] );
+
   // Description:
   // Set the dataset pointer for a given node. This will resize the number of
   // levels and the number of datasets in the level to fit level, id requested.