CityGen is a runtime C++ plugin for Unreal Engine 5 that turns infinite procedural terrain into a city-builder sandbox — players draw roads, place buildings, and paint zones at runtime, on a streaming open world that generates around them. Drop the WorldStreamingManager into your level, set up the RTS camera, and you have the core of a city-builder, RTS, or 4X game running before lunch.
Playable Demo | Documentation | Discord Community
V1.3 Day & Night | V1.2 Sidewalks, Bridges, Props | V1.1 Fab Release | V0.6 Zoning | V0.5 Buildings | V0.4 Save/Load | V0.3 Bridges | V0.2 Roads | V0.1 Camera
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RUNTIME, NOT EDITOR-TIME
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CityGen is NOT an editor-time city generator. Tools like iPCC, CityBLD, and UE5's built-in Landscape Splines generate cities at edit time, baked into your level. CityGen runs at game time — your players draw the roads, paint the zones, and watch buildings appear. Different category, different problem solved.
Built on the WorldGen terrain core. Every WorldGen feature is included — you do not need WorldGen separately to use CityGen.
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CITY-BUILDER FEATURES
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▸ Player-Drawn Road Tool
▸ Day / Night System (V1.3) — drop-in `CityGenTimeOfDay` actor drives sun + moon, post-process exposure, SkyLight recapture, and a smoothly-ramped `Illuminate` MPC scalar. Configurable lit window with 30 min smooth fade. PreviewInEditor for live scrubbing.
▸ Sidewalks (V1.2) — parallel spline-mesh strips on every ground road tile.
▸ Linear-Z Road Grade — roads stay flush on rolling terrain between control points; mesh and chunk-flattened bed match exactly
▸ Junctions
▸ Fixed-Angle Bends — single-midpoint arc anchor with bisector tangent, clean 90° corners with no facet artifacts
▸ Spline-Mesh Road Rendering — local-average tangent override eliminates Catmull-Rom overshoot on asymmetric spacing
▸ Bridges — automatic span detection over rivers / valleys, per-segment bridge mesh + pillars with hysteresis
▸ Roadside Props — Data asset per road asset, one ISM per mesh. Per-type spacing/side/scale/rotation, bridge filter, `bExtendToGround` pylon mode, collision toggle, pivot-agnostic placement.
▸ Roadside Prop Zone Filter (V1.2) — per-prop toggles for Dezoned / Residential / Commercial / Industrial. Sidewalk strip inherits nearest-cell zone; bridges bypass filter.
▸ Roadside Prop Carve-Aware Placement (V1.2) — props read Z from actual carved road grade; never spawn on a crossing road's deck; rebuild deferred until chunks settle.
▸ Building Placement Tool
▸ Footprint-Aware Building Z (V1.2) — placement Z = max of a 3×3 grid inside the rotated footprint. Deep base hides downhill gap; never buried on slopes. Applied to ghost, commit, auto-zone fill, and save/load.
▸ Zoom-Safe Cursor + Clicks (V1.2) — RTS max zoom-out resolves cursor + Road / Demolish / Zone clicks via deproject + long line-trace fallback.
▸ Cities-Skylines Grid Snap + OBB-vs-OBB SAT Collision — buildings align to nearest road's tangent, footprint OBB tests against all other buildings
▸ Slope-Aware Refusal — per-asset MaxSlopeDegrees blocks placement on terrain too steep
▸ Multi-Cell Footprints + Mesh Variants + Per-Placement Height Roll — all persisted in save
▸ Zoning System — Cities-Skylines zone painting, per-segment 2D cell grid, 4×4 brush per click, weighted building pools per zone asset
▸ Zone Auto-Fill — paint a cell, get a building; erase a cell, the building disappears. Origin-cell tracking. Manual buildings survive zoning. Junction-aware. Dezones on demolish.
▸ Demolish Mode — X key, removes buildings and road segments
▸ RTS Camera Pawn — Enhanced Input, zoom-aware pan speed, auto-pitch on zoom, middle-mouse pan, right-mouse orbit with damping
▸ HUD API
▸ Save / Load (F5/F9)
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INHERITED FROM WORLDGEN CORE
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▸ Infinite Chunk Streaming — actor pool, no spawn/destroy at runtime
▸ Async Mesh + Collision — thread-pool geometry; bUseAsyncCooking default
▸ Seamless Chunk Normals — 1-vertex border overlap eliminates seams
▸ Layered Noise — Layer 0 is the continental mask for all later layers
▸ CLMNoise — Perlin / Simplex / Cellular / Ridged Multifractal / Domain Warp. No third-party deps.
▸ Biome Blending — vertex color weights: Grass / Rock / Snow / Beach / Underwater
▸ Spatial Biomes — temperature + humidity fields → Tundra / Boreal / Desert / Tropical
▸ Beach Layer — height band above sea level, baked into UV1.x
▸ ISM Foliage + Dense Grass — data-asset driven, no BVH spike, slope-sink clustering
▸ Hydraulic Erosion — particle droplet sim, fully async
▸ LOD + Far Terrain — per-ring resolutions plus outer low-res horizon ring
▸ Terrain Deformation — runtime spherical brushes, persistent across rebuilds
▸ Exclusion Volumes — flatten + foliage suppression in a box region
▸ Actor Spawner System — biome/slope/height-filtered, consumed-position tracking
▸ Terrain Query API — SampleTerrainAt / GetHeightAtWorldPos, sync, BP-callable
▸ Multiplayer Support — streams around all connected players
▸ Water Plane — follows player, covers full view distance
▸ Editor Preview — Preview / Clear Terrain buttons
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TECHNICAL HIGHLIGHTS
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▸ Pure C++ runtime — Blueprint-friendly exposed parameters
▸ ProceduralMeshComponent-based geometry
▸ Virtual Shadow Maps + Distance Field Shadows by default
▸ Enhanced Input throughout — Input Mapping Context drives camera and modes
▸ Spline-mesh road + sidewalk rendering with linear-Z grade
▸ One ISM per prop mesh — shared collision body, no per-instance cook hitch
▸ CLMNoise — original noise library, no external dependencies
▸ Seeded RNG per chunk — deterministic foliage, grass, variants, zone fills
▸ MPSC upload queue — worker-thread mesh uploads, frame-time bounded
▸ Cursor-raycast placement Z — matches rendered mesh, not analytic noise
▸ Listen / client / dedicated server — no extra setup
▸ Nanite compatible — ISM foliage, grass, and props
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INCLUDED
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▸ Full C++ source
▸ RTS camera pawn + player controller blueprints
▸ In game UI
▸ Pre-built landscape material with biome blending
▸ Sample road, building, and zone data assets
▸ 15 pre-composed building scene meshes — 5 residential plot scenes (house + yard + props), 5 commercial scenes (tower / shop / plaza), 5 industrial scenes (warehouse + lot + props)
▸ Bridge prop mesh set — pylon, weight distributor, lamp post, with paired materials (M_Concrete, M_Pole, M_Light)
▸ Sidewalk pavement mesh + concrete material (V1.2)
▸ DA_Road preconfigured with RoadProps entries: pylons (extend-to-ground, bridge-only), weight distribution slabs, and lamp posts (both-sides + mirrored); sidewalk fields populated
▸ Sample foliage and grass data assets
▸ Sample tree, pine, and grass meshes with materials
▸ Sample spawner data asset and demo actor
▸ Demo map
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PERFECT FOR
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City builders, real-time strategy games, 4X prototypes, tycoon and management games, survival colonies, base-building games, and any project that needs a player-shaped open world — roads, buildings, and zones — on top of streaming procedural terrain without writing road geometry, building placement, zoning, or chunk management code from scratch.
