Add a LayerData class and a Job class to create it from a Protobuf message

ProcessSlicedObjectListJob.py

@@ -0,0 +1,37 @@
+from UM.Job import Job
+from UM.Scene.Iterator.DepthFirstIterator import DepthFirstIterator
+from UM.Scene.SceneNode import SceneNode
+from UM.Application import Application
+from UM.Mesh.MeshData import MeshData
+
+from . import LayerData
+
+import numpy
+import struct
+
+class ProcessSlicedObjectListJob(Job):
+    def __init__(self, message):
+        super().__init__(description = 'Processing sliced object', visible = True)
+        self._message = message
+        self._scene = Application.getInstance().getController().getScene()
+
+    def run(self):
+        objectIdMap = {}
+        for node in DepthFirstIterator(self._scene.getRoot()):
+            if type(node) is SceneNode and node.getMeshData():
+                objectIdMap[id(node)] = node
+
+        for object in self._message.objects:
+            mesh = objectIdMap[object.id].getMeshData()
+
+            layerData = LayerData.LayerData()
+            for layer in object.layers:
+                for polygon in layer.polygons:
+                    points = numpy.fromstring(polygon.points, dtype='i8') # Convert bytearray to numpy array
+                    points = points.reshape((-1,2)) # We get a linear list of pairs that make up the points, so make numpy interpret them correctly.
+                    points = numpy.asarray(points, dtype=numpy.float32)
+                    points /= 1000
+                    points = numpy.insert(points, 1, layer.id / 10, axis = 1)
+                    layerData.addPolygon(layer.id, polygon.type, points)
+
+            mesh.layerData = layerData