ENH: Enhance ability to render quadratic surfaces.

These changes are designed to enhance the rendering of surfaces that come from unstructured grids that have quadratic cells.  Whereas before every quadratic face was tessellated on the control points, these changes allow you to select a subdivision level in vtkDataSetSurfacefilter used to convert the quadratic faces to approximating linear polygons.

There has also been some support added for rendering correct wireframes from the extracted surface.  This includes changing the painters to support a new vtkDataSetAttributes::EDGEFLAG that hides the internal edges of the approximating polygons.

Author: Kenneth Moreland

Filtering/vtkCellType.h

@@ -29,7 +29,8 @@
 // GetCell() and vtkGenericCell::SetCellType(). Also, to do the job right,
 // you'll also have to modify some filters (vtkGeometryFilter...) and
 // regression tests (example scripts) to reflect the new cell addition.
-// Also, make sure to update vtkCellTypesStrings in vtkCellTypes.cxx.
+// Also, make sure to update vtkCellTypesStrings in vtkCellTypes.cxx
+// and the vtkCellTypes::IsLinear method in vtkCellTypes.h.
 
 // .SECTION Caveats
 // An unstructured grid stores the types of its cells as a

Filtering/vtkCellTypes.h

@@ -118,6 +118,13 @@ class VTK_FILTERING_EXPORT vtkCellTypes : public vtkObject
   // defined in vtkCellType.h)
   static int GetTypeIdFromClassName(const char* classname);
 
+  // Description:
+  // This convenience method is a fast check to determine if a cell type
+  // represents a linear or nonlinear cell.  This is generally much more
+  // efficient than getting the appropriate vtkCell and checking its IsLinear
+  // method.
+  static int IsLinear(unsigned char type);
+
 protected:
   vtkCellTypes();
   ~vtkCellTypes();
@@ -148,5 +155,11 @@ inline int vtkCellTypes::IsType(unsigned char type)
   return 0;
 }
 
+//-----------------------------------------------------------------------------
+inline int vtkCellTypes::IsLinear(unsigned char type)
+{
+  return ((type <= 20) || (type == VTK_CONVEX_POINT_SET));
+}
+
 
 #endif

Filtering/vtkDataSetAttributes.cxx

@@ -50,7 +50,9 @@ ::AttributeNames[vtkDataSetAttributes::NUM_ATTRIBUTES][12] =
   "TCoords",
   "Tensors",
   "GlobalIds",
-  "PedigreeIds" };
+  "PedigreeIds",
+  "EdgeFlag"
+};
 
 const char vtkDataSetAttributes
 ::LongAttributeNames[vtkDataSetAttributes::NUM_ATTRIBUTES][35] =
@@ -60,7 +62,9 @@ ::LongAttributeNames[vtkDataSetAttributes::NUM_ATTRIBUTES][35] =
   "vtkDataSetAttributes::TCOORDS",
   "vtkDataSetAttributes::TENSORS",
   "vtkDataSetAttributes::GLOBALIDS",
-  "vtkDataSetAttributes::PEDIGREEIDS" };
+  "vtkDataSetAttributes::PEDIGREEIDS",
+  "vtkDataSetAttributes::EDGEFLAG"
+};
 
 //--------------------------------------------------------------------------
 // Construct object with copying turned on for all data.
@@ -1072,6 +1076,7 @@ ::NumberOfAttributeComponents[vtkDataSetAttributes::NUM_ATTRIBUTES] =
   3,
   9,
   1,
+  1,
   1};
 
 //--------------------------------------------------------------------------
@@ -1084,6 +1089,7 @@ ::AttributeLimits[vtkDataSetAttributes::NUM_ATTRIBUTES] =
   MAX,
   EXACT,
   EXACT,
+  EXACT,
   EXACT};
 
 //--------------------------------------------------------------------------

Filtering/vtkDataSetAttributes.h

@@ -90,6 +90,7 @@ class VTK_FILTERING_EXPORT vtkDataSetAttributes : public vtkFieldData
     TENSORS=4,
     GLOBALIDS=5,
     PEDIGREEIDS=6,
+    EDGEFLAG=7,
     NUM_ATTRIBUTES
   };
 
@@ -165,6 +166,7 @@ class VTK_FILTERING_EXPORT vtkDataSetAttributes : public vtkFieldData
   //  vtkDataSetAttributes::TENSORS = 4
   //  vtkDataSetAttributes::GLOBALIDS = 5
   //  vtkDataSetAttributes::PEDIGREEIDS = 6
+  //  vtkDataSetAttributes::EDGEFLAG = 7
   // Returns the index of the array if succesful, -1 if the array 
   // is not in the list of arrays.
   int SetActiveAttribute(const char* name, int attributeType);