# Storing data a pass makes with custom sample positions for a subsequent pass Inform Metal when your app uses programmable sample positions for its depth render targets or copies MSAA depth data. ## Discussion A render or compute pass usually stores its target’s depth data in a compressed format. Any subsequent pass has to use the correct sample positions to decompress the data before reading it. You can store depth data in a representation that uses arbitrary sample positions (see [Positioning samples programmatically](/documentation/Metal/positioning-samples-programmatically)). > Important: > You can sample depth positions programmatically only on devices that support programmable sample positions (see ``doc://com.apple.metal/documentation/Metal/MTLDevice/areProgrammableSamplePositionsSupported``). When your app uses custom sampling positions, inform Metal by setting the [`MTLRenderPassColorAttachmentDescriptor`](/documentation/Metal/MTLRenderPassColorAttachmentDescriptor) or [`MTLRenderPassDepthAttachmentDescriptor`](/documentation/Metal/MTLRenderPassDepthAttachmentDescriptor) instance’s [`storeActionOptions`](/documentation/Metal/MTLRenderPassAttachmentDescriptor/storeActionOptions) property to [`customSamplePositions`](/documentation/Metal/MTLStoreActionOptions/customSamplePositions). This setting tells Metal that any subsequent pass that reads the attachment may not know the sample positions the current pass uses to generate the data. Examples of a pass that can use custom sample positions include the following: - A fragment shader that uses unique, programmable sample positions - A blit pass that copies MSAA depth data to another resource In this scenario, Metal may decompress the depth render target and store the uncompressed data. > Tip: > Improve the performance of a pass if its programmable sample positions are the same for the next pass by setting the descriptor’s ``doc://com.apple.metal/documentation/Metal/MTLRenderPassAttachmentDescriptor/storeAction`` property to ``doc://com.apple.metal/documentation/Metal/MTLStoreAction/store`` and clearing the ``doc://com.apple.metal/documentation/Metal/MTLStoreActionOptions/customSamplePositions`` option from the ``doc://com.apple.metal/documentation/Metal/MTLRenderPassAttachmentDescriptor/storeActionOptions`` property. --- 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)