“the memory consumption seems less aggressive”
My first guess would be that importing tiles directly into UE5 World Partition requires a lot of GPU memory to create the Landscape Section textures, and that will all be done on the GPU.
Whereas simply converting an existing UE4 Level will already have those Section textures created, they just have to be moved over into LandscapeStreamingProxy actors in UE5 (the textures don’t have to be re-created).
So the amount of video memory would be really low on a conversion versus an import since it isn’t creating new terrain Section MIP LOD Textures. If you follow what I mean.
Any Windows software will have available to it both Dedicated and Shared video memory to use for the texture creation step in importing.
The Dedicated memory is how much memory is physically on the video card, such as 8GB, 10GB, 12GB, 24GB, etc.
The Shared memory is calculated as 50% of the computer system’s installed main memory. So if you have a system with 64GB of main memory, the Shared video memory will be 50% of that or 32GB.
This means that on a system with 64GB of main memory and a 10GB RTX-3080, the total amount of video memory available for rendering textures etc is 32GB + 10GB = 42GB.
Depending on the amount of video memory required for the import process, you might run out of video memory during LandscapeStreamingProxy texture creation, in which case the only way to resolve that is to either purchase a video card with more Dedicated memory, or increase the system’s main memory in order to increase the Shared memory amount.
Note however, that UE5 World Partition has totally different world sizes than UE4 World Composition, so converting any Landscape from UE4 to UE5 will either crop or pad the Landscape world size. Which might be a bad thing depending on what you want and what exactly happens in the conversion. I personally wouldn’t do it.
UE4 World Composition used tiles of Recommended Landscape Sizes as defined in the UE4 Landscape documentation, such as 8x8 tiles of 1009x1009 tile sizes with shared edges. which would result in terrain Section sizes of either 63 or 127, and Components that are either 1x1 or 2x2 Sections.
World Partition does NOT do this! It uses an entirely new sizing method, based on Section sizes of 511 (not 63 or 127). My guess is to get the number of Drawcalls lower for rendering large terrains in World Partition.
This means that totally different Landscape sizes will have to be used for World Partition.
You can calculate the new valid World Partition sizes as (511 x N) - (N-1).
So for example, some of the valid World Partition resolutions are:
16321
24481
28561
32641
44881
48961
This also means that to create a tile set for import, you will have to determine what tile multiplier dimensions are valid. Most World Partition resolutions only have one tile size set value available for them, because they are such odd numbers.
For example:
16321 is only divisible by 19 × 859
24481 is a prime number
28561 is divisible by 13 × 2197 or 169 × 169
32641 is only divisible by 7 × 4663
44881 is only divisible by 37 × 1213
48961 is only divisible by 11 × 4451