Thanks for providing the starting point here, you piqued my interest.There are a few things you need to consider here:The Data() constructor takes the number of bytes, not objects, so you need to multiply the count by the stride.SIMD3<Float> is 4 floats wide, not 3. The underlying data in this case is tightly packed triples of floats.The indices are uInt32, not uInt16.Here's my working version, with these issues corrected:extension ARMeshGeometry { func toMDLMesh(device: MTLDevice) -> MDLMesh { let allocator = MTKMeshBufferAllocator(device: device); let data = Data.init(bytes: vertices.buffer.contents(), count: vertices.stride * vertices.count); let vertexBuffer = allocator.newBuffer(with: data, type: .vertex); let indexData = Data.init(bytes: faces.buffer.contents(), count: faces.bytesPerIndex * faces.count * faces.indexCountPerPrimitive); let indexBuffer = allocator.newBuffer(with: indexData, type: .index); let submesh = MDLSubmesh(indexBuffer: indexBuffer, indexCount: faces.count * faces.indexCountPerPrimitive, indexType: .uInt32, geometryType: .triangles, material: nil); let vertexDescriptor = MDLVertexDescriptor(); vertexDescriptor.attributes[0] = MDLVertexAttribute(name: MDLVertexAttributePosition, format: .float3, offset: 0, bufferIndex: 0); vertexDescriptor.layouts[0] = MDLVertexBufferLayout(stride: vertices.stride); return MDLMesh(vertexBuffer: vertexBuffer, vertexCount: vertices.count, descriptor: vertexDescriptor, submeshes: [submesh]); } }