https://github.com/EpicGames/UnrealEngine/pull/14543
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VK_FORMAT_R8G8B8A8_SRGB more efficient than VK_FORMATB8G8R8A8 SRGB，on PICO4 Ultra Qualcomm XR Gen2 SoC( Both supported PF_B8G8R8A8 and PF_R8G8B8A8 on PICO xr runtime). Why Quest3 doesn’t have issue is because that Quest3’s runtime doesn’t support PF_B8G8R8A8, then fallback to PF_R8G8B8A8. Do you have other good ideal？
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Currently, we can set r.DefaultBackBufferPixelFormat to 4 to trigger below logic.
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One of our testing demo，at 90FPS base，two formats has about 14FPS difference.
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Just wanted to update you that we will be taking this for UE 5.8. A version of the change is currently in review.
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Hi Seamus,
I’ve submitted a modified version of the PR to UE/Main in CL 53076595. Please take a look when you get a chance and let me know if there are any issues. This should also end up in UE 5.8.
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One information，xrEnumerateSwapchainFormats returns rgba8 and bgra8, and on pico we put rgba8 ahead of bgra8, but you know, the contain logic above chose bgra8 directly. I am not sure if some varable format can use xrEnumerateSwapchainFormats return order（for loop chose the first）, some specific format （ue must）use contain. But currently the pr can fix this issue, but I am not sure if some other attachment has similar performance issue, maybe no issue anymore. [Image Removed]
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r.DefaultBackBufferPixelFormat or add a new backbuffer format rgba8 in addition to bgra8
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Where can I take a look the CL 53076595? Do you have a link on GitHub?
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