# renderTargetArrayIndexOffset An offset into the list of render targets. ``` var renderTargetArrayIndexOffset: UInt32 ``` ## Discussion To specify a list of offsets, call the [`setVertexAmplificationCount(_:viewMappings:)`](/documentation/Metal/MTLRenderCommandEncoder/setVertexAmplificationCount(_:viewMappings:)) method. When your app renders to different render targets, you specify the render target index to render to in your vertex shader by adding the `render_target_array_index` attribute to one of the vertex shader’s outputs. If you are using vertex amplification, Metal calculates the index for each amplified vertex by adding the index offset for the vertex to the value returned from your shader. --- 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)