Add ConvexHullJob and ConvexHullNode that can be used for Convex hull calculations and display

ConvexHullJob.py

@@ -0,0 +1,32 @@
+from UM.Job import Job
+from UM.Application import Application
+from UM.Math.Polygon import Polygon
+
+import numpy
+
+from ConvexHullNode import ConvexHullNode
+
+class ConvexHullJob(Job):
+    def __init__(self, node):
+        super().__init__()
+
+        self._node = node
+
+    def run(self):
+        if not self._node or not self._node.getMeshData():
+            return
+
+        mesh = self._node.getMeshData()
+        vertexData = mesh.getTransformed(self._node.getWorldTransformation()).getVertices()
+
+        hull = Polygon(numpy.rint(vertexData[:, [0, 2]]).astype(int))
+
+        # First, calculate the normal convex hull around the points
+        hull = hull.getConvexHull()
+        # Then, do a Minkowski hull with a simple 1x1 quad to outset and round the normal convex hull.
+        hull = hull.getMinkowskiHull(Polygon(numpy.array([[-1, -1], [-1, 1], [1, 1], [1, -1]], numpy.float32)))
+
+        hull_node = ConvexHullNode(self._node, hull, Application.getInstance().getController().getScene().getRoot())
+
+        self._node._convex_hull = hull
+        delattr(self._node, "_convex_hull_job")

ConvexHullNode.py

@@ -0,0 +1,72 @@
+from UM.Scene.SceneNode import SceneNode
+from UM.Resources import Resources
+from UM.Math.Color import Color
+from UM.Math.Vector import Vector
+from UM.Mesh.MeshData import MeshData
+
+import numpy
+
+class ConvexHullNode(SceneNode):
+    def __init__(self, node, hull, parent = None):
+        super().__init__(parent)
+
+        self.setCalculateBoundingBox(False)
+
+        self._material = None
+
+        self._original_parent = parent
+
+        self._inherit_orientation = False
+        self._inherit_scale = False
+
+        self._node = node
+        self._node.transformationChanged.connect(self._onNodePositionChanged)
+        self._node.parentChanged.connect(self._onNodeParentChanged)
+        #self._onNodePositionChanged(self._node)
+
+        self._hull = hull
+
+        hull_points = self._hull.getPoints()
+        center = (hull_points.min(0) + hull_points.max(0)) / 2.0
+
+        mesh = MeshData()
+        mesh.addVertex(center[0], 0.1, center[1])
+
+        for point in hull_points:
+            mesh.addVertex(point[0], 0.1, point[1])
+
+        indices = []
+        for i in range(len(hull_points) - 1):
+            indices.append([0, i + 1, i + 2])
+
+        indices.append([0, mesh.getVertexCount() - 1, 1])
+
+        mesh.addIndices(numpy.array(indices, numpy.int32))
+
+        self.setMeshData(mesh)
+
+    def render(self, renderer):
+        if not self._material:
+            self._material = renderer.createMaterial(Resources.getPath(Resources.ShadersLocation, 'basic.vert'), Resources.getPath(Resources.ShadersLocation, 'color.frag'))
+
+            self._material.setUniformValue('u_color', Color(35, 35, 35, 128))
+
+        renderer.queueNode(self, material = self._material, transparent = True)
+
+        return True
+
+    def _onNodePositionChanged(self, node):
+        #self.setPosition(node.getWorldPosition())
+        if hasattr(node, "_convex_hull"):
+            delattr(node, "_convex_hull")
+            self.setParent(None)
+
+
+        #self._node.transformationChanged.disconnect(self._onNodePositionChanged)
+        #self._node.parentChanged.disconnect(self._onNodeParentChanged)
+
+    def _onNodeParentChanged(self, node):
+        if node.getParent():
+            self.setParent(self._original_parent)
+        else:
+            self.setParent(None)