New option for detecting feature edges at material boundaries.

A checkbox "Material Boundaries" has been added to the Freestyle
options in the Layers tab of the Render buttons.  By enabling the
option, any edge between two faces with different materials is
detected as a feature edge.  In style modules, edges at material
boundaries can be tested with pyNatureUP1D(Nature.MATERIAL_BOUNDARY).

source/blender/freestyle/intern/application/Controller.cpp

@@ -114,6 +114,7 @@ Controller::Controller()
   _ComputeRidges = true;
   _ComputeSteerableViewMap = false;
   _ComputeSuggestive = true;
+  _ComputeMaterialBoundaries = true;
   _sphereRadius = 1.0;
 
 	init_options();
@@ -466,6 +467,7 @@ void Controller::ComputeViewMap()
   edgeDetector.enableOrthographicProjection(proj[3][3] != 0.0);
   edgeDetector.enableRidgesAndValleysFlag(_ComputeRidges);
   edgeDetector.enableSuggestiveContours(_ComputeSuggestive);
+  edgeDetector.enableMaterialBoundaries(_ComputeMaterialBoundaries);
   edgeDetector.setSphereRadius(_sphereRadius);
   edgeDetector.setSuggestiveContourKrDerivativeEpsilon(_suggestiveContourKrDerivativeEpsilon);
   edgeDetector.processShapes(*_winged_edge);
@@ -647,6 +649,7 @@ void Controller::setComputeRidgesAndValleysFlag(bool iBool){
 bool Controller::getComputeRidgesAndValleysFlag() const {
   return _ComputeRidges;
 }
+
 void Controller::setComputeSuggestiveContoursFlag(bool b){
   _ComputeSuggestive = b;
 }
@@ -654,6 +657,15 @@ void Controller::setComputeSuggestiveContoursFlag(bool b){
 bool Controller::getComputeSuggestiveContoursFlag() const {
   return _ComputeSuggestive;
 }
+
+void Controller::setComputeMaterialBoundariesFlag(bool b){
+  _ComputeMaterialBoundaries = b;
+}
+  
+bool Controller::getComputeMaterialBoundariesFlag() const {
+  return _ComputeMaterialBoundaries;
+}
+
 void Controller::setComputeSteerableViewMapFlag(bool iBool){
   _ComputeSteerableViewMap = iBool;
 }