Fixed drop to buildplate issue with 3mf

CURA-382

cura/PlatformPhysics.py

@@ -82,7 +82,7 @@ class PlatformPhysics:
 
             # Move it downwards if bottom is above platform
             move_vector = Vector()
-            if Preferences.getInstance().getValue("physics/automatic_drop_down") and not (node.getParent() and node.getParent().callDecoration("isGroup")): #If an object is grouped, don't move it down
+            if Preferences.getInstance().getValue("physics/automatic_drop_down") and not (node.getParent() and node.getParent().callDecoration("isGroup")) and node.isEnabled(): #If an object is grouped, don't move it down
                 z_offset = node.callDecoration("getZOffset") if node.getDecorator(ZOffsetDecorator.ZOffsetDecorator) else 0
                 move_vector = move_vector.set(y=-bbox.bottom + z_offset)
 

plugins/3MFReader/ThreeMFReader.py

@@ -148,4 +148,5 @@ class ThreeMFReader(MeshReader):
             translation = Vector(x=-global_container_stack.getProperty("machine_width", "value") / 2, z=0,
                                  y=global_container_stack.getProperty("machine_depth", "value") / 2)
             result.translate(translation)
+        result.setEnabled(False) # The result should not be moved in any way, so disable it.
         return result