Added an extruded convex hull as a raft instead of a grey plane.

- New shader transparent_object.shader
- Raft thickness is calculated in BuildVolume and used in
  ConvexHullDecorator, notified by a Signal.
- Removed old grey plane from BuildVolume.
- Vertex data below build plane is no longer discarded (caused convex
  hulls that are too small).
- Uses new functions in MeshBuilder (update Uranium as well).

CURA-1707

cura/BuildVolume.py

@@ -13,6 +13,7 @@ from UM.Math.Color import Color
 from UM.Math.AxisAlignedBox import AxisAlignedBox
 from UM.Math.Polygon import Polygon
 from UM.Message import Message
+from UM.Signal import Signal
 
 from UM.View.RenderBatch import RenderBatch
 from UM.View.GL.OpenGL import OpenGL
@@ -49,6 +50,8 @@ def approximatedCircleVertices(r):
 class BuildVolume(SceneNode):
     VolumeOutlineColor = Color(12, 169, 227, 255)
 
+    raftThicknessChanged = Signal()
+
     def __init__(self, parent = None):
         super().__init__(parent)
 
@@ -69,7 +72,6 @@ class BuildVolume(SceneNode):
 
         self._raft_thickness = 0.0
         self._adhesion_type = None
-        self._raft_mesh = None
         self._platform = Platform(self)
 
         self._active_container_stack = None
@@ -103,8 +105,6 @@ class BuildVolume(SceneNode):
         renderer.queueNode(self, mesh = self._grid_mesh, shader = self._grid_shader, backface_cull = True)
         if self._disallowed_area_mesh:
             renderer.queueNode(self, mesh = self._disallowed_area_mesh, shader = self._shader, transparent = True, backface_cull = True, sort = -9)
-        if self._raft_mesh and self._adhesion_type == "raft":
-            renderer.queueNode(self, mesh=self._raft_mesh, transparent=True, backface_cull=True, sort=-9)
 
         return True
 
@@ -153,17 +153,6 @@ class BuildVolume(SceneNode):
             mb.setVertexUVCoordinates(n, v[0], v[2])
         self._grid_mesh = mb.build()
 
-        # Build raft mesh: a plane on the height of the raft.
-        mb = MeshBuilder()
-        mb.addQuad(
-            Vector(min_w, self._raft_thickness, min_d),
-            Vector(max_w, self._raft_thickness, min_d),
-            Vector(max_w, self._raft_thickness, max_d),
-            Vector(min_w, self._raft_thickness, max_d),
-            color=Color(128, 128, 128, 64)
-        )
-        self._raft_mesh = mb.build()
-
         disallowed_area_height = 0.1
         disallowed_area_size = 0
         if self._disallowed_areas:
@@ -221,6 +210,9 @@ class BuildVolume(SceneNode):
             " \"Print Sequence\" setting to prevent the gantry from colliding"
             " with printed objects."), lifetime=10).show()
 
+    def getRaftThickness(self):
+        return self._raft_thickness
+
     def _updateRaftThickness(self):
         old_raft_thickness = self._raft_thickness
         self._adhesion_type = self._active_container_stack.getProperty("adhesion_type", "value")
@@ -232,9 +224,11 @@ class BuildVolume(SceneNode):
                 self._active_container_stack.getProperty("raft_surface_layers", "value") *
                     self._active_container_stack.getProperty("raft_surface_thickness", "value") +
                 self._active_container_stack.getProperty("raft_airgap", "value"))
+
         # Rounding errors do not matter, we check if raft_thickness has changed at all
         if old_raft_thickness != self._raft_thickness:
             self.setPosition(Vector(0, -self._raft_thickness, 0), SceneNode.TransformSpace.World)
+            self.raftThicknessChanged.emit()
 
     def _onGlobalContainerStackChanged(self):
         if self._active_container_stack: