This is the post up-above that described the solution: Runtime virtual texture sets landscape to lower mip - #57 by cannasoftware
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Use the following console command to show the pools around residency:
r.VT.Residency.Show 1
You should see some graphs like such (you do this whilst running, not in editor):
The line tracks consumption, starts at the bottom and rises as pages/resources are consumed from a given pool. If the red-line reaches the top you are consuming all the resources in that pool and need more (you’re bottoming-out).
In your ‘C:\Program Files\Epic Games\UE_5.3\Engine\Config\BaseEngine.ini’ file, locate a section like this:
[/Script/Engine.VirtualTexturePoolConfig]
; Configure VT physical memory pools. Usefull commands to set these
; “stat virtualtexturing” show dynamic use of the VT system including the cache loads
; “r.VT.ListPhysicalPool” list in-depth details on the allocated physical pools
; The upper allocation limit for a pool is caluclated by matching a size and format from the list below or falling back to the default
DefaultSizeInMegabyte=64
+Pools=(SizeInMegabyte=96, MinTileSize=0, MaxTileSize=9999, Formats=(PF_DXT1, PF_DXT5))
+Pools=(SizeInMegabyte=512, MinTileSize=0, MaxTileSize=9999, Formats=(PF_A32B32G32R32F))
+Pools=(SizeInMegabyte=128, MinTileSize=0, MaxTileSize=9999, Formats=(PF_DXT5, PF_DXT5))
Add/futz-with the values for the pool that is bottoming-out. Test, repeat.