Summary
Landscape texture precision collapse (pixelation and gray fallback) on Vulkan SM5 (Windows/Linux) is incorrectly governed by the “Mobile” Float Precision Mode setting in UE 5.7.
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Creative
What Type of Bug are you experiencing?
Assets
Steps to Reproduce
- Open or create a project in Unreal Engine 5.7.
- Create a Landscape and apply a material with a standard texture (e.g., a grid or check texture).
- Set the project’s Default RHI to Vulkan and the Shader Format to SM5.
- Move the camera or landscape component several thousand units away from the world origin (0,0,0).
- Observe the landscape texture becoming pixelated and eventually turning gray (sampling failure).
- Navigate to Project Settings > Rendering > Mobile and change Float Precision Mode from “Default” to “Full Float”.
- Restart the editor/recompile shaders and observe that the pixelation is eliminated.
Expected Result
The “Mobile” precision settings should not impact the Desktop Vulkan SM5 rendering path. Desktop Vulkan should default to Full Float (FP32) for landscape vertex factories to maintain LWC compatibility, consistent with DX11 and DX12.
Observed Result
The Vulkan SM5 Desktop renderer uses the Mobile FP16 precision setting, causing a precision collapse on large-scale landscapes that is not present in other Desktop RHIs.
Platform(s)
Windows 10, Desktop Vulkan SM5, UE5.7
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Additional Notes
This behavior suggests that the 5.7 shader headers for LandscapeVertexFactory are using the GET_PRECISION macro tied to the Mobile.FloatPrecisionMode CVar even when compiled for VULKAN_SM5_PC, which breaks UV interpolation at a distance.