Merge Parts

You built a model out of several pieces that push into each other: a crate with planks and bolts, a robot from boxes and cylinders, a kit-bashed prop. This template merges them into one closed mesh. The faces hidden inside other pieces are removed, the pieces are sealed together where they meet, and every piece keeps its own material and textures.

Start

On the start screen, click Merge Parts under Create from Template. The new project opens on a small sample model that comes with Forge, and cooks. It is named Merge Parts; rename it any time by clicking its name in the menu bar.
The Import node is selected: choose your model’s .glb under File there, and the chain cooks again on it. Or drop the .glb on the card in step 1 to start with it straight away. Starting from File ▸ New from Template ▸ Merge Parts instead, you name the project first; it opens on the same sample.
Wait for the chain to cook. The viewport shows the Clean node: your merged model, exactly as it will export.
On the Transform node, set Fit length to the model’s real height, or turn Fit size off if the model already has its real size.
On the Export node, choose a file inside your game project and click Export.

The chain

Import

Load the model and its parts.
Transform

Give it its real size and stand it on the ground.
Boolean

Merge every part into one closed solid.
Clean

Remove the slivers left along the seams.
Export

Write the merged .glb.

Boolean has only its first input wired, with Operation set to Union. With one input it merges every shape inside that mesh: where two parts overlap, the faces inside the other part go, and the two are joined along the line where they meet. Each piece of the result keeps its part’s material, texture coordinates and shading.
Clean removes the few faces with no area a merge can leave along its seams. Remove small pieces is off, so a small part that touches nothing, such as a loose bolt, is kept.

When to use it

Use Merge Parts on a model that is already fine piece by piece and only needs its pieces sealed into one surface: for a single solid shape, a collision hull, a 3D print, or to stop the game drawing faces nobody can see. It keeps the model’s own triangles and textures.

Use AI mesh cleanup on a messy, dense model, such as an AI export or a scan: it rebuilds the mesh at a triangle budget with new UVs and baked textures, but does not merge overlapping parts.

Settings worth changing

Transform ▸ Fit length: the model’s real height. Fit size off keeps the size it has.
Clean ▸ Remove small pieces: turn it on to drop tiny floating fragments.

Check the result

Select the Clean node and look at the stats under its parameters: one piece for parts that overlapped, and no open or non-manifold edges. Parts that touch nothing stay separate pieces.

Limitations

Each part should be a closed solid. A flat card or an open shell has no inside, so it can’t be merged cleanly with what it overlaps.
The file keeps one object per part. Export writes each part back into its own object from the file, with the parts meeting exactly along their seams. Join them in your 3D tool if you need a single object.
The result is triangles, like any imported model.