So, I've been wanting to make new worlds for TS4 and have been trying to learn more about the world files, however they seem poorly researched with a lot of people saying that it can't be done and leaving it at that. However since people have found that you can duplicate worlds I've been somewhat determined to find a way to actually create/edit world files. This might be a lost cause as actually editing them might cause the game to throw a tantrum, though I haven't tested that yet. I've been trying to get a better idea of what I'm editing before playing with anything so that I know where to look to find any edits I might make and if the game is undoing them. Here's what I've discovered so far:

• The .world files appear to be editable with Sims 4 Studio if renamed to [worldname].package (instead of [worldname].world)

  I have not tried changing anything yet to see if the changes will stick or if the game auto-detects edits

• I think the weird images with primary colors (for example instance 0010000000800080 in BG_Engagement_03) are blend maps used for telling the game where to paint grass, dirt, stone, etc.
• the "Water Mask List" contains a list of mask instances. I'm guessing these are for weather effects? I don't have Seasons so I can't really test this.

  BG_Engagement_03's water masks are split between ClientDeltaBuild6.package and ClientDeltaBuild7.package (I might have missed some though)
  I have no idea how to create a package to override these to test them (I'm basically brand-new to sims modding), even if I had Seasons.

• There is a "Terrain Height Map" type. However I'm not sure what that is and where, or even if, they're actually pointing anywhere. However it's wayyyy too large for the 4-ish lines of text it contains. I'm guessing this might be an image or something that isn't being read correctly by S4S.
• There are files with the "Terrain Mesh" type that contain a list of vertices.
• I don't know what "Unknown World [X]" corresponds to, however in BG_Engagement_03 it references U1, U2, U3, U4, which are also referenced in the "Terrain Size Info" of the file.

I know a lot of this is probably pretty basic, however I'm hoping others might have more info or it might spark others to do research into this as well. I also hope at least some of this is new. I'll try to remember to add anything else as I continue to play with this. Additionally if anyone has more info or has links to tutorials related to this, please let me know.

(also, sorry if this is the wrong forum)

Thank you for the info. You can maybe try asking these creators for more info on your project, if they are willing to divulge (I don't think the first two will but worth a try).
TwistedMexi is rumored to be working on an actual world creating tool and has shown small hints of it (he has already altered the UI to display the icon, which you can see in his videos).
Arnie/TheSimsPlus is currently the one with lots of world editing evidence, not only making some worlds swim-able but altering them to be "open world", and has been looking into new worlds as well.
denton47 said they plan to look into it eventually and is also the one who figured out how to edit VFX, which people also claimed to not be touchable (even more so than worlds!!).
There's one other who succeeded in creating a bare-bones new world (literally just the terrain and it was blocky), but I'm not sure if I'm allowed to say who as last I checked I don't think they are interested in going further, and I don't think they'd appreciate random people asking about new worlds. I can ask though if they'd be willing to give any info they have?
For basic editing I know Lunanelfeah has done some work on this, as she was the one who discovered editing lot sizes as well as the skybox and made tutorials on them, and I have yet to see anyone else publish their info on worlds.
There are just the ones I know of, but I'm sure there's at least a few more who aren't public.

Luna's tutorials:
Lot sizes: https://docs.google.com/document/d/...uvMDblyecA/edit
Skybox: https://lunanelfeah.tumblr.com/post...tutorial-sims-4

And I don't know if you ever saw the thread, but here is the original duplicating world's tutorial: https://www.modthesims.info/showthread.php?t=636296

And there is this one about lighting, but it's about updating not editing. There was one about editing but the person placed it under a "keep reading" and deleted their tumblr.
https://dreadpirate.tumblr.com/post...hting-mods-this