Customize roads and grid

Roads and the placement grid define where buildings can exist. This tutorial covers BP_CBT_Grid, BP_Road, BP_RoadTile, and BP_Vehicle.

Road pipeline

flowchart TD
  Input[PrimaryClick on BP_Road spline] --> Preview[PreviewRoad mesh]
  Preview --> Create[CreateRoad]
  Create --> Tile[Spawn BP_RoadTile per point]
  Tile --> Type[Internal_UpdateRoadType]
  Type --> Save[AddRoadToSave]
  Tile --> Traffic[BP_Vehicle traces tiles]

1. Change grid size

Two grid values matter in the shipped template:

Blueprint	Property	Shipped default	Role
BP_CBT_PlayerController	Grid Size	200	Placement snap for buildings and roads
BP_CBT_Grid	Default Grid Size	100	Visual grid cell size
BP_CBT_Grid	Grid Divisions	4	Subdivisions per cell

1. Open Blueprints/Misc/BP_CBT_Grid (placed in DemoMap) to change the visual grid.
2. Open BP_CBT_PlayerController → Class Defaults to change placement snap (Grid Size).
3. Compile and verify BFL_CBT_GlobalFunctions → GridSnap_Float still aligns previews.

Caution

Changing grid size on an existing save desynchronizes stored transforms. Reset DemoMap or start a new save after large grid changes.

Example — finer placement

Setting	Shipped default	Example
Grid Size (controller)	200	100 for half-cell placement snap
Default Grid Size (grid actor)	100	Match controller or keep visual grid separate

Rebuild a test road and house after changing either value.

2. Road meshes and materials

BP_RoadTile properties:

Property	Purpose
RoadMeshComponent	Instanced mesh per tile
RoadType	ERoadType → mesh selection
Materials	Set on mesh or via CreateDynamicMaterialInstance

Example — wider roads

1. Duplicate the straight road static mesh under Meshes/ (or scale in mesh asset).
2. Assign the new mesh on BP_RoadTile for ERoadType::Straight.
3. Update BP_Road → PreviewRoad mesh to match.

3. Intersections and lamps

BP_RoadTile graph functions:

Function	Role
Internal_UpdateRoadType	Picks straight vs corner vs Fourway from neighbours
Internal_UpdateToFourwayIfRequired	Promotes crossing tiles
Internal_AddLampToStraightRoad	Spawns lamp mesh on straights

To disable street lamps, clear or bypass Internal_AddLampToStraightRoad on BP_RoadTile.

Example — four-way only intersections

1. Open BP_RoadTile Event Graph.
2. Trace Internal_UpdateRoadType branches.
3. Force Fourway only when ≥3 neighbours connect; otherwise keep Straight.

4. Road placement UX

BP_CBT_PlayerController:

Property / function	Tweak
bShowRoadDebugSpheres	Visualize snap points while learning
Internal_PreviewRoad / ClearPreviewRoad	Ghost colour/material
CreateRoad	Finalize and deduct currency (if wired)

BP_Road:

Function	Tweak
SetSplinePoints	Point density along curves
RemoveSplinePoint	Undo last click

5. Ambient traffic

BP_Vehicle drives on BP_RoadTile chains.

Function	Behaviour
Internal_TraceForRoadTile	Finds next tile
Internal_PlayTimeline	Moves along spline
Internal_OnDayStarted / Internal_OnNightStarted	Visibility with day cycle

Example — fewer vehicles at night

1. Open BP_Vehicle.
2. On Internal_OnNightStarted, pause or hide mesh (pattern already present — tune timers).
3. Confirm BP_CBT_SaveGame → AddVehicle still restores traffic on load.

6. Collision channel

Roads use GenericRoad (ECC_GameTraceChannel2). Building placement traces GenericBuilding against road overlaps.

If custom meshes fail placement checks:

1. Verify mesh collision profile = GenericRoad or GenericBuilding.
2. Confirm Config/DefaultEngine.ini channel definitions are migrated (see Migrate tutorial).

Example presets

Preset	Grid Size (controller)	Road notes
Compact city	100	Shorter BP_Road spline segments
Highway layout	200 (default)	Wider straight mesh, disable lamps
Pedestrian plaza	300+	Fewer tiles; rely on large commercial footprints

Test checklist

1. Draw an L-shaped road — corner tile updates via Internal_UpdateRoadType.
2. Place a House on a cell touching GenericRoad — bIsNearRoad = true.
3. Bulldoze a middle tile — neighbouring tiles refresh type.
4. Save, reload, confirm RoadSaveArray restores mesh variants.

Next

• Migrate into your project
• Blueprint reference — BP_Road / BP_RoadTile