我正在尝试在 Freecad 上创建两个立方体并将两个立方体合并。你能告诉我为什么立方体变得“透明”吗？还有，如何合并这些立方体？代码下方：
import Fem
#cube1
cube1 = Fem.FemMesh()
cube1.addNode( 0, 0, 0, 1)
cube1.addNode( 10, 0, 0, 2)
cube1.addNode(10, 10, 0, 3)
cube1.addNode(0, 10, 0, 4)
cube1.addNode( 0, 0, 10, 5)
cube1.addNode( 10, 0, 10, 6)
cube1.addNode(10, 10, 10, 7)
cube1.addNode(0, 10, 10, 8)
cube1.addVolume([1,2,3,4,5,6,7,8])
obj = App.ActiveDocument.addObject("Fem::FemMeshObject", "cube1")
obj.FemMesh = cube1
#cube2
cube2 = Fem.FemMesh()
cube2.addNode( 0, 0, 10, 1)
cube2.addNode( 10, 0, 10, 2)
cube2.addNode(10, 10, 10, 3)
cube2.addNode(0, 10, 10, 4)
cube2.addNode( 0, 0, 20, 5)
cube2.addNode( 10, 0, 20, 6)
cube2.addNode(10, 10, 20, 7)
cube2.addNode(0, 10, 20, 8)
cube2.addVolume([1,2,3,4,5,6,7,8])
obj = App.ActiveDocument.addObject("Fem::FemMeshObject", "cube2")
obj.FemMesh = cube2
obj.Placement.Base = FreeCAD.Vector(0, 0, 0)
obj.ViewObject.DisplayMode = "Faces, Wireframe & Nodes"
