SCNMathExtensions is a small Swift library that provides commonplace math extensions for SceneKit's SCNVector3, SCNQuaternion, & SCNMatrix4 types, and bridging from/to GLKVector3, simd.float3, GLKQuaternion, GLKMatrix4, & simd.float4x4.
The master branch is Swift 5.x, and build overlays (the minimal changeset to the Package.swift, xcodeproj, and other build files) of the current library version are available on the swift-4.2, swift-4, and swift-3 branches. (Note: I don't check that these are built as often as I used to when Swift 4.2 or 4.0 were the latest versions, but their changes haved worked and I've merged new library versions into them since then.)