# MeshResource.ShapeExtrusionOptions.ExtrusionMethod.tracePositions(_:) Extrudes the shape by sweeping it along a piecewise-linear curve. ``` case tracePositions([SIMD3]) ``` ## Discussion The curve is defined as the set of line segments For each edge in the provided curve, the swept shape (e.g. the 2D path provided in `MeshResource(extruding: Path)`, or text) will be instantiated at the edge’s endpoints. Each instance of the swept shape will be joined together by a strip of geometry. The positions are traced in such a way as to avoid twist in the generated 3D shape. When possible, the local y-axis of the swept (2D) shape will be aligned with the y-axis of the generated 3D shape. For example, extrude a rounded square along the z-axis, while zig-zagging in the y-axis: ```swift // Positions in a zig-zag pattern. let positions: [SIMD3] = [ [0, 0, 0], [0, -0.1, 0.2], [0, 0, 0.4], [0, -0.1, 0.6] ] var extrusionOptions = ShapeExtrusionOptions() extrusionOptions.extrusionMethod = .tracePositions(positions) ```  --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)