func process(polygon: [MyVector]) throws -> (vertices: [MyVector], indices: [Int])? { let polygon: [MyVector] = ... // This should be an array of vertices - must have at least an `x` and `y` coordinate pairs! guard let tess = TessC() else { print("Something went wrong while initializing TessC! :c") return nil } // Size of polygon (number of points per face) let polySize = 3 // Map from MyVector to CVector3 (LibTessSwift's vector representation) let contour = polygon.map { CVector3(x: TESSreal($0.x), y: TESSreal($0.y), z: 0.0) } // Add the contour to LibTess tess.addContour(contour) // Tesselate - if no errors are thrown, we're good! try tess.tessellate(windingRule: .evenOdd, elementType: .polygons, polySize: polySize) // Collect resulting vector var result: [MyVector] = [] var indices: [Int] = [] // Extract vertices for vertex in tess.vertices! { result.append(MyVector(x: vertex.x, y: vertex.y)) } // Extract each index for each polygon triangle found for i in 0..<tess.elementCount { for j in 0..<polySize { let index = tess.elements![i * polySize + j] if (index == -1) { continue } indices.append(index) } } return (result, indices) } // Use away! guard let (verts, indices) = try process(myVerts) else { return } MyRenderer.drawPolygon(verts: verts, indices: indices)