Hello,
I am having the same issue with UE v4.27.2
I am trying to package for the ASTC platform (for Oculus Quest 2) using Virtual Textures (but no Runtime Virtual Textures) and the package always fails with:
Assertion failed: CompressedFormat == PF_Unknown || CompressedFormat == CompressedMip[0].PixelFormat [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Engine/Private/VT/VirtualTextureDataBuilder.cpp] [Line: 676]
I am using OpenGL and not Vulkan.
It is kinda annoying since I really need to use VT because of the very large textures I am using (importing UDIM textures).
I don’t really understand why this error occurs since the compression format of my textures seems to be OK (DXT1 for color maps and BC5 for normal maps) and works fine when I am not using Virtual Textures.
Did you solve this problem by any chance ?
EDIT: This failure happens when the “Enable virtual texture support on mobile” option is enabled