MarchingCubes is now able to not generate normals.

vtkm/worklet/MarchingCubes.h

@@ -129,9 +129,11 @@ public:
 
     VTKM_CONT_EXPORT
     IsosurfaceGenerate(FieldType isovalue,
+                       bool generateNormals,
                        const vtkm::worklet::ScatterCounting& scatter,
                        IdPortalConstType edgeTable) : EdgeTable(edgeTable),
                                                       Isovalue(isovalue),
+                                                      GenerateNormals(generateNormals),
                                                       Scatter(scatter) {  }
 
     template<typename CellShapeTag,
@@ -185,25 +187,35 @@ public:
         vertexOut[triVertex] = vtkm::Lerp(coords[edgeVertex0],
                                           coords[edgeVertex1],
                                           interpolant);
-        const vtkm::Vec<vtkm::FloatDefault,3> edgePCoord0 =
-            vtkm::exec::ParametricCoordinatesPoint(
-              fieldIn.GetNumberOfComponents(), edgeVertex0, shape, *this);
-        const vtkm::Vec<vtkm::FloatDefault,3> edgePCoord1 =
-            vtkm::exec::ParametricCoordinatesPoint(
-              fieldIn.GetNumberOfComponents(), edgeVertex1, shape, *this);
-        const vtkm::Vec<vtkm::FloatDefault,3> interpPCoord =
-            vtkm::Lerp(edgePCoord0, edgePCoord1, interpolant);
-        normalsOut[triVertex] =
-            vtkm::Normal(vtkm::exec::CellDerivative(
-                           fieldIn, coords, interpPCoord, shape, *this));
+
         interpolationIds[triVertex][0] = indices[edgeVertex0];
         interpolationIds[triVertex][1] = indices[edgeVertex1];
         interpolationWeights[triVertex] = interpolant;
+
+        //conditionally do these only if we want to generate normals
+        if(this->GenerateNormals)
+        {
+          const vtkm::Vec<vtkm::FloatDefault,3> edgePCoord0 =
+              vtkm::exec::ParametricCoordinatesPoint(
+                fieldIn.GetNumberOfComponents(), edgeVertex0, shape, *this);
+          const vtkm::Vec<vtkm::FloatDefault,3> edgePCoord1 =
+              vtkm::exec::ParametricCoordinatesPoint(
+                fieldIn.GetNumberOfComponents(), edgeVertex1, shape, *this);
+
+          const vtkm::Vec<vtkm::FloatDefault,3> interpPCoord =
+              vtkm::Lerp(edgePCoord0, edgePCoord1, interpolant);
+
+          normalsOut[triVertex] =
+            vtkm::Normal(vtkm::exec::CellDerivative(
+                           fieldIn, coords, interpPCoord, shape, *this));
+        }
+
       }
     }
 
   private:
     const FieldType Isovalue;
+    bool GenerateNormals;
     ScatterType Scatter;
   };
 
@@ -271,6 +283,7 @@ public:
 
     vtkm::worklet::ScatterCounting scatter(numOutputTrisPerCell, DeviceAdapter());
     IsosurfaceGenerate isosurface(isovalue,
+                                  true, //always generate normals.
                                   scatter,
                                   edgeTable.PrepareForInput(DeviceAdapter()));
 

vtkm/worklet/ScatterCounting.h

@@ -137,11 +137,6 @@ struct SubtractToVisitIndexKernel : vtkm::exec::FunctorBase
 ///
 struct ScatterCounting
 {
-  VTKM_CONT_EXPORT
-  ScatterCounting()
-  {
-  }
-
   template<typename CountArrayType, typename Device>
   VTKM_CONT_EXPORT
   ScatterCounting(const CountArrayType &countArray, Device)