I solved the problem after watching this tutorial video: Unreal Engine 4 Tutorial: Collision (english) - YouTube
Basically, I hadn’t set up any collisions. Here’s what I did:
- Created a new test object in Blender: a boolean difference of an outer torus (scaled along normals) minus an inner torus, creating a hollow torus-tube with non-zero wall thickness.
- Exported to FBX
- Ran it through the FBX 2013 converter
- Dragged the resulting file into the Content Browser
- Double-clicked the imported object in the content browser
- In the object editor, in the details pane, under Static Mesh settings, set “Collision Complexity” to “Use Complex Collisions as Simple”
- From the Collision menu, chose Auto Convex Collision
- In the Convex Decomposition Panel, set Max Hulls to 24 and Max Hull Verts to 32
- Apply
- Tested object in the simulator, and can collide with the outside shell (starting outside), and the inside wall (starting inside).