Round convex hull data to 0.1mm, then remove duplicates

This greatly reduces convex hull complexity while at the same
time not introducing much error into the convex hull. This keeps
things responsive when dealing with more complex models.

Contributes to CURA-1387

cura/ConvexHullJob.py

@@ -40,6 +40,14 @@ class ConvexHullJob(Job):
             vertex_data = mesh.getTransformed(self._node.getWorldTransformation()).getVertices()
             # Don't use data below 0. TODO; We need a better check for this as this gives poor results for meshes with long edges.
             vertex_data = vertex_data[vertex_data[:,1] >= 0]
+
+            # Round the vertex data to 1/10th of a mm, then remove all duplicate vertices
+            # This is done to greatly speed up further convex hull calculations as the convex hull
+            # becomes much less complex when dealing with highly detailed models.
+            vertex_data = numpy.round(vertex_data, 1)
+            duplicates = (vertex_data[:,0] == vertex_data[:,1]) | (vertex_data[:,1] == vertex_data[:,2]) | (vertex_data[:,0] == vertex_data[:,2])
+            vertex_data = numpy.delete(vertex_data, numpy.where(duplicates), axis = 0)
+
             hull = Polygon(vertex_data[:, [0, 2]])
 
         # First, calculate the normal convex hull around the points