Unable to use Concave representation of physics shape

Question

Whenever I assign a Concave physics shape

let physicsShape = SCNPhysicsShape(node: starNode, options: [SCNPhysicsShapeTypeKey:SCNPhysicsShapeTypeConcavePolyhedron])
starNode.physicsBody = SCNPhysicsBody(type: SCNPhysicsBodyType.Dynamic, shape: physicsShape)

the starNode just falls through all other nodes. I created starNode in Blender. I also noticed that in Scene Editor I am unable to assign PhysicsShapeType of starNode to Concave. Why is this happening and how do I fix it? The Convex shape type is out of question because it is an inaccurate representation of geometry.

Answer 1

From the docs:

SCNPhysicsShapeTypeConcavePolyhedron

The physics shape is a concave polyhedron closely following the surface of the geometry.

This option provides the highest level of detail, at a high cost to simulation performance. Use it only for irregularly shaped bodies where precise collision behavior is crucial to your app’s design.

This shape type may only be used for static physics bodies (that is, those whose type property is SCNPhysicsBodyTypeStatic).

If you need a dynamic shape to be concave, your best bet is to create a compound shape from multiple SCNPhysicsShape objects (or from an hierarchy of nodes and their geometry).