Pipeline guide

Export procedural buildings to Unreal Engine.

Use GLB for the first building test, preserve the metric source, and verify one representative asset before importing the complete city. The checks below separate a reliable handoff from a visually plausible but inconsistent one.

Last updated: 26 July 2026

First choiceGLB for one compact building file
ImporterUnreal Engine Interchange / glTF workflow
Initial scale1.0, followed by a known-dimension check
Final passMaterials, collision and optimisation in Unreal Engine

Before export

Freeze the useful source state

Save the complete Metropolygonia preset and seed before download. The exported mesh is a snapshot; the preset is what makes the design meaningfully editable. If a later review changes floor count, façade rhythm or interior scope, correct the source parameters and export again.

Give the project and building a stable, descriptive name.
Check whether interior rooms, partitions, slabs and stairs are actually required.
Orbit the model and inspect section or geometry views for intersections and missing surfaces.
Identify a known dimension that can be measured after import.
Choose GLB unless a downstream requirement specifically calls for glTF, OBJ or STL.

Single building

Import a GLB through Interchange

Export the building as GLB
The file contains the glTF scene and binary geometry together, and can embed the generated image textures. Keeping the handoff self-contained reduces missing-resource errors.
Use Unreal Engine's current import path
Bring the file into the Content Browser through the current Interchange-based workflow. Epic changes options between releases, so use the documentation for the Unreal version in your project rather than copying an old preset blindly.
Start at scale 1.0
Metropolygonia stores model dimensions in metres and the city manifest declares metres. Import at 1.0 first, then measure the known doorway, storey or footprint dimension.
Keep semantic parts when useful
Avoid combining every imported static mesh automatically when separate generated parts or material assignments matter to your editing and optimisation plan.
Inspect before placing instances
Check normals, pivots, openings, interior circulation, UVs and material-slot names. Fix source or import problems before duplicating the asset across a level.

Refer to Epic's official pages for Interchange asset import and glTF support when checking current version-specific behaviour.

City package

Understand the ZIP before importing it

The Unreal city package is organised for asset-level control. It is not simply one merged city mesh. The current archive contains:

buildings/SM_###_name.glb — one GLB for each placed building, reset to a local origin for independent use.
chunks/chunk_.../terrain/SM_Terrain.glb — terrain clipped to one 256 × 256 m chunk and stored relative to its origin.
chunks/chunk_.../roads/SM_Roads.glb — road, sidewalk, curb and marking geometry for that chunk.
chunks/chunk_.../infrastructure/SM_Infrastructure.glb — foundations and city stairs intersecting that chunk.
manifest.metropolygonia-city.json — project units, bounds, origins, stable material IDs, dependencies and building transforms.
README_UE.txt — a compact package-specific import reminder.

Manifest version 3 keeps the version-2 building transforms and adds physically partitioned terrain, road and infrastructure resources. Place each chunk GLB at its originMeters; its vertices are already chunk-local. Buildings keep their own local pivots and use the transform recorded in the manifest.

Incremental packages

A package created for selected dirty chunks contains only those files. Check exportScope.includedChunkIds before replacing resources in an existing Unreal project.

Import one building first

A representative test reveals scale, UV and material decisions before you spend time processing every asset in the package.

Validation

A five-part acceptance check

1. Scale

Measure the known reference and compare it with the intended metric value. Also compare door and storey proportions against an Unreal mannequin or other trusted reference.

2. Geometry

Look for flipped normals, open seams, coplanar flicker, intersecting access elements and missing section surfaces. Review interiors from inside, not only through an exterior orbit.

3. Materials and textures

Confirm material slots remain distinguishable and expected image textures arrived. A successful preview is not yet a final PBR shader; author or replace production materials in Unreal Engine.

4. UVs

Apply a tiled checker to several differently sized elements. At multiplier 1, the intended base convention is one repeat per 2 × 2 metres. Adjust the Unreal material tiling for the selected library and art direction.

5. Runtime requirements

Decide collision, LOD or Nanite strategy, lightmap handling, instancing and streaming from the actual target platform and camera distance. The generator cannot infer those project constraints.

Material boundary

Use the current handoff honestly

GLB and glTF can carry named materials and embedded or referenced image data; the Metropolygonia exporter waits for pending texture work before creating a model. OBJ uses MTL plus PNG sidecar files, and STL contains geometry only.

Supported PBR materials and their image maps are available in model exports. Material grouping and consistent UV coordinates remain the reliable handoff; refine the Unreal graph for normal intensity, packed channels, surface variation and platform-specific shader cost.

Continue with the 2 × 2 m UV guide for a tiled-material setup, or compare the full handoff boundaries in the export format reference.

Freeze the useful source state

Import a GLB through Interchange

Export the building as GLB

Use Unreal Engine's current import path

Start at scale 1.0

Keep semantic parts when useful

Inspect before placing instances