How does 3dmax look inside the door?

1. Place a camera inside the object and observe it through the camera view. A camera is like the position of a person's eyes. When the camera is placed in an object, it is equivalent to people entering the object.

2. Select the cube and add the Edit Polygon modifier.

3. Select the polygon level, click a face, and then press the Delete key to delete (for Mac, press the fn+Delete key).

4. Turn the angle, and you can see that the interior of the cube is hollow.