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I believe the OP is talking about the WWDC app. I had a similar confusion. If you try to copy the actual text of the code snippets that you see in the "code" section, you just get a link to the WWDC session. If though, you click on the timestamp, the video will start playing at that section, and in the top left overlay of the video player there is a copy icon, and if you tap that while the snippet is on screen, the code itself gets copied. Its great that you can copy from the video itself, but pretty confusing that you can't copy from the code snippets view
Looks like the missing initializer for export was added in beta 2:
https://developer.apple.com/documentation/uikit/uidocumentpickerviewcontroller/3566731-init?changes=latest_beta
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You can get round this by using ModelIO to create your geometry, and using its methods to compute tangents. This seems to work:import SceneKit
import ModelIO
import SceneKit.ModelIO // not sure why this is needed
let mesh = MDLMesh(sphereWithExtent: float3(repeating: 1), segments: uint2(32, 16), inwardNormals: false, geometryType: .triangles, allocator: nil)
mesh.addTangentBasis(forTextureCoordinateAttributeNamed: MDLVertexAttributeTextureCoordinate, normalAttributeNamed: MDLVertexAttributeNormal, tangentAttributeNamed: MDLVertexAttributeTangent)
let sphere = SCNGeometry(mdlMesh: mesh)
