Why is unpacking VPK files so difficult?

I’ve tried 3 different tools for unpacking VPK files.

The one contained inside GMod (vpk.exe) pretended to work, but did nothing.
Some other tool I tried that I forgot the name of was just totally broken.
GCFScape seems to think that all vpk files are empty.

How am I supposed to make an Antlion-Barnacle hybrid if I can’t even access their models and scripts?

Unpacking .VPK files isn’t that difficult, dude. You just need to know which files actually needs to be opened. The files you want to open are the .VPK files that end with _dir in the name (i.e., hl2_misc_dir.vpk for the models, hl2_textures_dir.vpk for the textures, etc.) for the content you’re wanting to extract. The numbered files always appear blank, but are required for the _dir files to be extractable.

Well, that explains a lot.
And now I find that I can’t even find the content I’m looking for amongst GMod’s dir.vpk files.
This file structure is insane.

The file structure is pretty consistent across all Source games, and in my opinion, very common-sense. What file are you looking for?

Antlion and barnacle stuff, obviously.
I really hope their content and scripts aren’t spread across 20 different files.

You won’t find the Antlion or Barnacle in GMod’s files. You need Half-Life 2 and/or its episodes for that content. You can find the files for the models and textures in the aforementioned examples I provided in my previous post.

It actually is in GMod’s files (/GarrysMod/sourceengine/)

Ah, my mistake then. I was mainly going by what I was seeing in the garrysmod_dir.VPK file.

I keep forgetting GMod went standalone some time ago, but I was never completely sure how.

So, how can I get started with making an Antlion-Barnacle hybrid?
I haven’t even been able to find the scripts for either anywhere.

That would be because there are no scripts for those NPCs. They are defined in the c++ code.

Darn, so I can’t reprogram their behaviours so that there’s giant Antlions that will occasionally shoot out a sticky tongue?

Well, technically, you can, but it isn’t going to be as easy as editing an existing script.

Consider that Doom is written in C, and yet, gmDoom and gmDoom Maps exist. Parts of the Doom code were hand-translated to Lua to make those addons work. You could theoretically re-implement the antlion npc in Lua, and give it whatever customizations you want.