Merge topic 'flying-edges-cell-fields'

8a9887023 Add regression test for flying edges interpolating cell fields
4f19ac608 Fix interpolation of cell fields with flying edges

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !3129

data/baseline/filter/contour-uniform-cellfield.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:0d4ecc87a7d69d32eb5a7ade1ce0daac57a3a09902accb2c3bba62f00c25b62f
+size 58412

docs/changelog/flying-edges-cell-fields.md

@@ -0,0 +1,5 @@
+# Fix interpolation of cell fields with flying edges
+
+The flying edges algorithm (used when contouring uniform structured cell
+sets) was not interpolating cell fields correctly. There was an indexing
+issue where a shortcut in the stepping was not incrementing the cell index.

vtkm/filter/contour/testing/RenderTestContourFilter.cxx

@@ -16,6 +16,7 @@
 
 #include <vtkm/filter/clean_grid/CleanGrid.h>
 #include <vtkm/filter/contour/Contour.h>
+#include <vtkm/filter/field_conversion/CellAverage.h>
 #include <vtkm/filter/field_transform/PointElevation.h>
 #include <vtkm/source/Tangle.h>
 
@@ -61,7 +62,6 @@ void TestContourFilterUniform()
   contour.SetMergeDuplicatePoints(true);
   contour.SetIsoValues({ 50, 100, 150 });
   contour.SetActiveField(fieldName);
-  contour.SetFieldsToPass(fieldName);
   vtkm::cont::DataSet result = contour.Execute(inputData);
 
   result.PrintSummary(std::cout);
@@ -70,6 +70,36 @@ void TestContourFilterUniform()
   vtkm::rendering::testing::RenderTestOptions testOptions;
   vtkm::rendering::testing::RenderTest(
     result, "pointvar", "filter/contour-uniform.png", testOptions);
+
+  std::cout << "Generate image for contour filter on a uniform grid with a cell field" << std::endl;
+  inputData = maker.Make3DUniformDataSet2();
+  VTKM_TEST_ASSERT(inputData.HasField(fieldName));
+
+  std::string cellFieldName = "elevation";
+  vtkm::filter::field_transform::PointElevation elevation;
+  vtkm::Bounds bounds = inputData.GetCoordinateSystem().GetBounds();
+  elevation.SetLowPoint(bounds.MinCorner());
+  elevation.SetHighPoint(bounds.MaxCorner());
+  elevation.SetRange(0, 1);
+  elevation.SetOutputFieldName(cellFieldName);
+  elevation.SetUseCoordinateSystemAsField(true);
+  inputData = elevation.Execute(inputData);
+
+  vtkm::filter::field_conversion::CellAverage point2cell;
+  point2cell.SetActiveField(cellFieldName);
+  point2cell.SetFieldsToPass(fieldName);
+  inputData = point2cell.Execute(inputData);
+
+  VTKM_TEST_ASSERT(inputData.HasPointField(fieldName));
+  VTKM_TEST_ASSERT(inputData.HasCellField(cellFieldName));
+
+  contour.SetIsoValues({ 80 });
+  result = contour.Execute(inputData);
+
+  result.PrintSummary(std::cout);
+
+  vtkm::rendering::testing::RenderTest(
+    result, cellFieldName, "filter/contour-uniform-cellfield.png", testOptions);
 }
 
 void TestContourFilterUniformBoundaries()

vtkm/filter/contour/worklet/contour/FlyingEdgesPass4Common.h

@@ -28,15 +28,19 @@ VTKM_EXEC inline vtkm::Id3 compute_incs3d(const vtkm::Id3& dims)
   return vtkm::Id3{ 1, dims[0], (dims[0] * dims[1]) };
 }
 
-VTKM_EXEC inline constexpr vtkm::Id increment_cellId(SumXAxis, vtkm::Id cellId, vtkm::Id)
+VTKM_EXEC inline constexpr vtkm::Id increment_cellId(SumXAxis,
+                                                     vtkm::Id cellId,
+                                                     vtkm::Id,
+                                                     vtkm::Id numToIncrement = 1)
 {
-  return cellId + 1;
+  return cellId + numToIncrement;
 }
 VTKM_EXEC inline constexpr vtkm::Id increment_cellId(SumYAxis,
                                                      vtkm::Id cellId,
-                                                     vtkm::Id y_point_axis_inc)
+                                                     vtkm::Id y_point_axis_inc,
+                                                     vtkm::Id numToIncrement = 1)
 {
-  return cellId + (y_point_axis_inc - 1);
+  return cellId + ((y_point_axis_inc - 1) * numToIncrement);
 }
 
 VTKM_EXEC inline bool case_includes_axes(vtkm::UInt8 const* const edgeUses)
@@ -159,6 +163,7 @@ struct Pass4TrimState
     cellId = compute_start(AxisToSum{}, ijk, pdims - vtkm::Id3{ 1, 1, 1 });
 
     //update our ijk
+    cellId = increment_cellId(AxisToSum{}, cellId, axis_inc, left - ijk[AxisToSum::xindex]);
     ijk[AxisToSum::xindex] = left;
 
     boundaryStatus[0] = FlyingEdges3D::Interior;