How to convert from ModelIO MDLMesh to SceneKit SCNGeometry and back?

Question

Apple have recently announced Model I/O Framework and, understandably, documentation is currently quite sparse with many classes still not fully documented. The Model I/O talk suggests a two-way link between SceneKit classes and Model I/O classes, but I can't find a way to do this in practice.

SCNGeometry has a convenience init which accepts a MDLMesh object, but I'm not sure how to go the other way and generate a MDLMesh object from a pre-existing SCNGeometry.

The init for MDLMesh is:

init(vertexBuffer vertexBuffer: MDLMeshBuffer,
     vertexCount vertexCount: Int,
     descriptor descriptor: MDLVertexDescriptor,
     submeshes submeshes: [MDLSubmesh])

or, alternatively, the same but with vertexBuffers: [MDLMeshBuffer] (where a vertex buffer corresponds to a SceneKit geometry source), I can't figure out where to go from here.

(It looks like MDLMeshBuffer has a method which takes a fillData: NSData parameter, and I know SCNGeometry.geometrySources gives an array of SCNGeometrySources each with a .data that provides these geometry sources as an NSData object, but I'm not sure if this is the right way to go about doing it.)

Any guidance would be much appreciated.

Answer 1

According to engineers in the labs at WWDC, the SceneKit to Model I/O bridge isn't in the first beta, but should show up in another beta later in the summer.