Convert the Ivy corner cubit to the new, 'universal' cubit creation method.
This forces deep changes to 'createRoundSolid' and the underlying 'MeshPolygon' class to make them support arbitrary Polygon 'centers of face convexity'.
Reason: the faces of this cubit are concave and such default 'center of face convexity' (which by default used to be (0,0)) turned to lie outside the face - which produces strange visual artifacts.
Convert the Ivy corner cubit to the new, 'universal' cubit creation method.
This forces deep changes to 'createRoundSolid' and the underlying 'MeshPolygon' class to make them support arbitrary Polygon 'centers of face convexity'.
Reason: the faces of this cubit are concave and such default 'center of face convexity' (which by default used to be (0,0)) turned to lie outside the face - which produces strange visual artifacts.