# setVertexBytes(_:length:index:) Creates a buffer from bytes and assigns it to an entry in the vertex shader argument table. ``` func setVertexBytes(_ bytes: UnsafeRawPointer, length: Int, index: Int) ``` ## Parameters `bytes` A pointer to argument data the method copies to an [`MTLBuffer`](/documentation/Metal/MTLBuffer) and assigns to an entry in the vertex shader argument table for buffers. `length` The number of bytes the method copies from the `bytes` pointer. `index` An integer that represents the entry in the vertex shader argument table for buffers that stores a record of the [`MTLBuffer`](/documentation/Metal/MTLBuffer) the method creates from `bytes`. ## Discussion The method is equivalent to creating an [`MTLBuffer`](/documentation/Metal/MTLBuffer) instance that contains the same data as `bytes` and calling the [`setVertexBuffer(_:offset:index:)`](/documentation/Metal/MTLRenderCommandEncoder/setVertexBuffer(_:offset:index:)) method. However, this method avoids the overhead of creating a buffer to store your data; instead, Metal manages the data. > Important: > Only call this method for single-use data that’s smaller than 4 KB. For data that’s more than 4 KB, create an [`MTLBuffer`](/documentation/Metal/MTLBuffer) instance and pass it to [`setVertexBuffer(_:offset:index:)`](/documentation/Metal/MTLRenderCommandEncoder/setVertexBuffer(_:offset:index:)). By default, the buffer at each index is `nil`. --- 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)