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[Metal][iOS] HDR and DepthOnly cause extra render passes



To reproduce:
1. Open attached project ""
2. Build for iOS
3. Deploy the Xcode project to an iOS device
4. After the project is loaded in Xcode menu bar press Debug > Capture GPU Frame
5. On the left column select FPS tab
6. Observe as there are three Blit operators (Hidden/BlitCopy, Final Blit, Hidden/BlitCopy)
7. In the same column observe that in CommandBuffer there are four RenderCommandEncoders

Expected: no extra RenderCommandEncoders and Bit operators can be seen
Actual: extra RenderCommandEncoders and Bit operators can be seen

Reproduced on:
2017.4.0f1 2017.4.30f1 2018.4.4f1 2019.1.10f1 2019.2.0b10

- The button to take GPU capture is not available after building with 2019.3.0a10
- On 2019.1 - 2019.2 there are three RenderCommandEncoders in CommandBuffer
- Disabling HDR on the Mian Camera there is one RenderCommandEncoder in CommandBuffer
- Setting Camera Clear Flags to Skybox there is one Blit in the FPS tab and two RenderCommandEncoders in CommandBuffer
- Only reproduces on Metal. Getting very different GPU frame capture results on OpenGLES3.

  1. Response avatar

    Resolution Note:

    when the first camera in frame is rendered and clear flags are depth only it *might* happen that intent of the user was to actually preserve color (like, they did manual rendering before or smth), thats why there are extra passes in the beginning - to copy contents of current RT
    as for HDR: it will render to 11.11.10 RT which needs to be be blit to system backbuffer (hence one extra blit in the end)

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