Add a LayerView plugin that can render sliced meshes

LayerView.py

@@ -0,0 +1,31 @@
+from UM.View.View import View
+from UM.View.Renderer import Renderer
+from UM.Scene.Iterator.DepthFirstIterator import DepthFirstIterator
+from UM.Resources import Resources
+
+class LayerView(View):
+    def __init__(self):
+        super().__init__()
+        self._material = None
+
+    def beginRendering(self):
+        scene = self.getController().getScene()
+        renderer = self.getRenderer()
+
+        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", [1.0, 0.0, 0.0, 1.0])
+
+        for node in DepthFirstIterator(scene.getRoot()):
+            if not node.render(renderer):
+                if node.getMeshData() and node.isVisible():
+                    try:
+                        layerData = node.getMeshData().layerData
+                    except AttributeError:
+                        continue
+
+                    renderer.queueMesh(layerData, node.getGlobalTransformation(), material = self._material, mode = Renderer.RenderLineLoop)
+
+    def endRendering(self):
+        pass