When I generate chunks, why and what are these other chunks with _s# .pak files?

Hello!

I’m using Generate Chunks for our project for the first time and I was following a tutorial from Epic while applying to our project. My project is using Unreal Engine 5.1 and I’m making chunks targeting for the iOS.

I understand that in the tutorial I’m following, if I set up a Primary Asset Label with a chunk ID 1 in a folder recursively, the assets inside it will be in a generated chunk with a name pakchunk1-ios.pak. However, in my project aside from that .pak file, there’s also other .pak files named pakchunk1_s1-ios.pak, pakchunk1_s2-ios.pak, etc.

The screenshot provided above is a snapshot of our project with 5 Primary Asset Labels with IDs 1 to 5.

So, as you can see there’s the files with pakchunk[chunk_id]_s[#]-[platform].pak.

  1. What are these extra _s#.pak files?
  2. What causes them to be created?
  3. How do I turn them back to singular pakchunk[chunk_id]-[platform].pak files?
  4. Do I need these .pak files with _s# to be distributed along with the ones without _s#?

As much as possible I prefer the ones without _s#.

Ok from what I understand now is that the .utoc and .ucas files are generated and required by the .pak files when the IoStore packaging option is enabled.

The _s# named pak files are called subchunks and it is usually generated when a particular chunk ID has exceeded its capacity limit. This can happen when you have set your packaging settings to limit the maximum file size a single chunk should be. These subchunks are equally as important as the other main chunks.

If you want to avoid these subchunks, ensure that the assets you assign to a chunk ID doesn’t cause to exceed limits.

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