Implement support for dumping and loading xmodel collisions

[Laupetin]

Currently OAT cannot dump collision data for xmodels and when creating new xmodels from 3D model files, there are no collisions created.

This sadly limits the usefulness of models for stuff like player models and zombies.

[JezuzLizard]

Fortunately the format of collmaps is the same as the .map files and you already have a mapfile dumper for IW4 I believe integrated in the project.

iwmap 4
"000_Global" flags  active
"The Map" flags 
// entity 0
{
"classname" "worldspawn"
// brush 0
{
 ( 23 27 -5 ) ( -16 27 -5 ) ( -16 -31 -5 ) clip_player 64 64 -18 56 0 0 lightmap_gray 16384 16384 -18 56 0 0
 ( -16 -31 5 ) ( -16 27 5 ) ( 23 27 5 ) clip_player 64 64 -18 56 0 0 lightmap_gray 16384 16384 -18 56 0 0
 ( -14 -16 6 ) ( 25 -16 6 ) ( 25 -16 -5 ) clip_player 64 64 -18 0 0 0 lightmap_gray 16384 16384 -18 0 0 0
 ( 16 -60 6 ) ( 16 -2 6 ) ( 16 -2 -5 ) clip_player 64 64 -56 0 0 0 lightmap_gray 16384 16384 -56 0 0 0
 ( 25 16 6 ) ( -14 16 6 ) ( -14 16 -5 ) clip_player 64 64 -18 0 0 0 lightmap_gray 16384 16384 -18 0 0 0
 ( -16 20 6 ) ( -16 -38 6 ) ( -16 -38 -5 ) clip_player 64 64 -56 0 0 0 lightmap_gray 16384 16384 -56 0 0 0
}
}
// entity 1
{
"origin" "0.0 0.0 0.0"
"model" "collision_geo_32x32x10"
"classname" "misc_model"
}

Example collmap from WaW mod tools used for a simple collision model for dynamic barriers to be spawnable.

Linking them is much harder though, any collision generating uses the bsp geo system. So you'll need to look at the XModel collision loadobj code to find out how they link them and what feature set they support out of the entire bsp compiling(I know they don't support meshes for instance).

[Laupetin]

Thanks for the additional context. The IW4 .map only covered the low hanging fruit, no brushes.
Therefore dumping will also require more looking into the code 😅

[JezuzLizard]

I think dumping is pretty easy at least compared to linking. Linking would require a partial reimplementation of the geometry compiling maps use, although I think the cod devs avoided changing the functionality and only extended it from game to game.

The "iwmap 4" token is the version of the format, I don't know when they last incremented it(the example was from WaW), it's possible that they didn't need to update the format even as late as T6 so maybe one implementation would work for all games.

[JezuzLizard]

Also you don't need this for player models or actors. Actors have their own engine defined mins/maxs and the bsp for every map is built around the players' collision boxes being a certain size which means it's not only not adjustable but it would likely be the hardest thing to change about any cod game.

The actual use case for collmaps on xmodels is for stuff like the care package or if someone wanted to say do a forge mode for CoD by overriding the stock models to have custom collisions. But it's not required for either of the examples you gave.

Now it would be one step closer to custom maps though...