World partition "grid size" and "region size".

Normally I would just google this sort of question but I get no useful results on this topic.

Google has no results found for “world partition region size” except for where I have asked this question.

None of the results for “world partition grid size”, at least the first 50 or so, answer my question.

I am feeling pretty stupid for not being able to understand what they mean by the tool-tip explanations. So could someone explain to me what these two settings actually change?

World Partition Grid Size: Number of components per landscape streaming proxies per axis

World Partition Region Size: Number of components per Landscape World Partition Region per axis

Is a streaming proxy the streaming source like the player character?

If the grid size is 2, does that mean 2 blocks on every side of the proxy? Does it mean 2 centered on the proxy?

The region size tool tip seems circular to me.

Thanks in advance.

I am glad that I am not the only person with this question. I am following a udemy course and they use a slightly older version of UE5 that doesn’t have the 2 separate properties, but if I follow along with the tutorial as is without changing those 2 properties, I end up, with what seems like, a world that is 2 somethings tall x 16 somethings wide. I am unsure of what those somethings are, but its definitely not square, which is what I intended on creating with my 32/32 number of components. Maybe the 2 x 16 grid represents what is visible to me from my current position? I don’t know. I will ask in the Discord channel associated with the course and see if anyone there knows, and post what I find here. Likewise, if you get an answer to the question, please update here as well

In the event someone else stumbles across this thread… To quote a Reddit thread (linked):

World Partition Grid Size: This determines the granularity of the landscape chunks, or proxies, that get streamed in and out. For instance, if you set the grid size to “2”, then your landscape will be divided into chunks where each chunk consists of 2x2 components. When the player moves around the world, these chunks (or proxies) get loaded/unloaded based on their proximity to the player.

World Partition Region Size: Regions are a higher-level organization structure in World Partition. While the Grid Size divides your landscape into smaller chunks, the Region Size groups these chunks into larger clusters.

The reason for having regions is to further optimize the streaming system. Instead of dealing with a huge number of individual chunks, the engine can handle a smaller number of regions, which each contain several chunks.

For better visualization, imagine a checkerboard. Each square on the checkerboard is a landscape component. If you have a “grid size” of 2, then every 2x2 block of squares is a streaming proxy. If you have a “region size” of 4, then every 4x4 block of these 2x2 proxies is a region.

Some helpful reference links:

https://www.reddit.com/r/unrealengine/comments/17err0b/world_partition_grid_size_and_region_size_question/
https://www.reddit.com/r/unrealengine/comments/18tbpzd/how_to_determine_a_performant_world_partition/

In case someone wants the 3 line explanation:

Grid size 1x1 or 2x2 - reduces drawcalls by 1/2 when set to 2x2.

Region size: number of “blocks” (components) that make up the lansscape.
256x256 = 65536 drawcalls at lod0.
The lower the number the best your performance.

Moral of the story?
Use meshes, not landscapes.