Editing the building and map files

Edit the building’s geometry

On the Edit building tab, set a region (a box in the building’s space: type its corners, Around the interior, Around the opening, or drag the six handles in the view) and press Edit the building here.

The model’s triangles inside become one mesh object with a slot per shader; each face keeps the building’s texture, UVs, normals and vertex colours.
Every collision file the region reaches becomes a collision object (boxes become their twelve triangles; each face keeps its collision material, flags and room id).
With With its decals and overlays (on), each model the building comes with that has faces in the region becomes a part of its own too (a decal on the wall you edit; see The models it comes with). A single one is taken whole with Edit its mesh on the Placement tab.
They sit in the Outliner’s Building group; the collision is coloured by material with a legend. The game’s own triangles inside the region are hidden while the parts exist.

Select a part and press Tab: every edit-mode tool works (see Mesh objects and edit mode). Properties offers a texture (slot) for the selected faces of the model, a collision material (the game’s materials.dat names) and the 16 collision flags, plus Collision from the model, Join coplanar faces and Revert (the game’s triangles come back).

On export the marks’ openings cut the building first, then each file a part belongs to has the original triangles of its region replaced; the files are written under the game’s names in stream/. Curved collision primitives in a region stay as the game has them. Picking another building drops the parts; a part of a model you untick is not exported (Problems says so).

Clear collision boxes

The game’s own collision inside a building (the map’s area files and the collision of the game’s interior standing in it, such as v_michael.ybn) often has walls and boxes exactly where your rooms and doorways are: the player is blocked although your interior is open there. A clear collision box is a box you place and move; on export every collision surface of the game inside it is removed.

Key	Action
`Shift`+`O`	Clear collision box tool: the strip over the view sets the size, a ghost follows the pointer and a click puts the box on the floor

The quickest way for a doorway: select the door or window and press Clear the game’s collision here (its Properties, Game collision). The box goes through the wall: the opening’s width plus a little, the wall’s thickness plus 40 cm each side, up to just over the head.
Move it with the arrows and the square, turn it with the ring, pull one of its six faces, or use the Scale tool; Properties has its position, size and turn. Edit > Add and the command palette make one too.
Keep the floor (on) starts the cut just above the game’s floor under the box, so nobody falls through; turn it off to cut the whole height.
The red collision lines in the view show the cut as you move the box. Properties and Problems say how much it took from which files, the floor it kept, and what still blocks.

A box belongs to the interior and moves with it. A hidden box still cuts; Cut on export off switches it off. Free interiors cut at the box’s place in the world. Not seen in game yet.

The game’s ground or floor that shows through your floor inside the rooms is a separate option: see The game’s floor inside the rooms.

Map files

The Map files tab lists what the game’s own files can undo that you cut.

Clear occluders over the openings (on): the area’s occlusion maps are written again without the box occluders that overlap an opening, and with model triangles inside it carved out, so the facade keeps occluding round the door.
Clear inside (Interior by default): the game hides whatever lies behind an occluder, and Rockstar puts box occluders inside its solid buildings, so an interior built in one stays invisible. The export clears them so the game does not hide your rooms:
- Interior writes each occlusion map again without the box occluders that overlap one of your rooms (a room’s box, 5 cm smaller all round) and with the occlude-model triangles there carved out;
- Building does the same for the whole building’s box;
- Off leaves them (Problems warns).
Show the occluders the export removes draws them in the view.
Replace the game’s interior (per interior listed, off): the map file that places a game MLO standing in the building is written again without it, so only your interior stands there; its doors and props go with it. With the option off the Problems warning stays.

Free and teleport interiors have the same check: on the Placement page, Occluders > Clear occluders inside the interior (on) writes the area’s occlusion maps without the occluders inside your rooms, wherever you placed the interior (for example in a building of the map or over one).

A file the last export wrote and this one does not is removed from the resource folder (the list is modlo_replaced_maps.txt). All of this is saved in the project and has not been seen in game yet.

Window prefabs

On a mark, Window prefab > Copy to a prefab copies the building’s own model of that window or doorway (and the overlay models standing there) into a prop under Assets/Models/<building>_window_NN/, keeping the shaders and embedding the textures they use.

Place in this opening puts it in the interior’s opening of that size as an ordinary prop, facing out of the wall. The Prop tool does the same for any opening prefab, and the prop’s model is written into the export’s stream/.