soc-2008-mxcurioni: Tested SWIG-less environment more and understood why the former predicate methods were not working. As Stéphane had mentioned a few months ago, Freestyle uses SWIG directors to provide cross-language polymorphism. The API and the system I had provided did not support that feature and only implementations in C++ were supported. To correct the problem, after researching how directors are implemented in SWIG, I provided the same functionality. So far, I only provided the code for the UnaryPredicate1D class and it works. The implementation is in intern/python/Director.cpp and Operators.cpp. I will port the remaining directors tonight and continue to test it.

To prevent strokes from piling up after each render,  I clear the canvas at each render now (as it should have been all along)

source/blender/freestyle/intern/python/Director.cpp

@@ -0,0 +1,12 @@
+#include "Director.h"
+
+#include "BPy_Convert.h"
+
+bool director_BPy_UnaryPredicate1D___call__( PyObject *py_up1D, Interface1D& if1D) {
+	cout << "Polymorphism works" << endl;
+
+	PyObject *method = PyObject_GetAttrString( py_up1D, "__call__");
+	PyObject *result = PyObject_CallFunction(method, "O", BPy_Interface1D_from_Interface1D(if1D) );
+
+	return bool_from_PyBool(result);
+}