Floor Placement — Dynamic Floor Plugin

Floor Placement

This page explains how the floor placement pipeline works — from user input to a committed polygon in the database and a rendered mesh on screen.

Overview: the placement pipeline

Player Input
    ↓
FloorPlacementControllerComponent
    ↓
Active Tool Actor (BP_ExampleRuntimeFloorPolygonToolActor)
    ↓
UFloorInputService  (via UDynamicFloorPluginSubsystem)
    ↓
Responsibility Handlers
  ├── UClickPointResponsibilityHandler  (for ClickPoint events)
  └── UFillEventResponsibilityHandler   (for Fill events)
    ↓
UPolygonDatabase
    ↓
UFloorPolygonChangeService  →  Notifies all IFloorPolygonChangeListener objects
    ↓
BP_FloorPolygonRenderer  →  Updates ProceduralMesh

Input Events

All floor actions are expressed as FFloorInputEvent structs sent to UFloorInputService.HandleInputEvent.

`FFloorInputEvent` fields

Field	Type	Description
`Kind`	`EFloorInputKind`	The type of action
`Position`	`FVector`	3D world position of the cursor/action
`Points`	`TArray<FVector2D>`	Optional: multiple 2D points at once
`MaterialId`	`int32`	Material to apply
`FloorType`	`EFloorType`	Floor layer type
`ApplyMode`	`EFloorInputApplyMode`	`Preview` or `Commit`
`SessionId`	`int32`	Session identifier
`bPointsAreRelative`	`bool`	Whether `Points` are relative positions

Input kinds (`EFloorInputKind`)

Kind	Meaning	Handler
`ClickPoint`	Place a single polygon at the cursor position	`UClickPointResponsibilityHandler`
`Fill`	Fill the enclosed area of the node network at the cursor	`UFillEventResponsibilityHandler`
`PolygonStart`	Begin a multi-vertex polygon placement	TODO verify: Blueprint-accessible?
`PolygonAddVertex`	Add a vertex to an in-progress polygon	TODO verify: Blueprint-accessible?
`PolygonComplete`	Finalize a multi-vertex polygon	TODO verify: Blueprint-accessible?
`SetMaterial`	Change the material of an existing polygon	—
`ToolChange`	Switch the active tool	—

Apply modes (`EFloorInputApplyMode`)

Mode	Description
`Preview`	Writes to the preview database only — no permanent change
`Commit`	Writes permanently to the production polygon database

The Tool Actor

BP_ExampleRuntimeFloorPolygonToolActor is the default placement tool. It implements UserFloorBpInterface and handles:

Key events and functions

Event / Function	Description
`OnBeginPlay`	Initializes the tool (tool shape, internal state)
`CurrentMouseHitResults`	Called every tick with current cursor hit results — used to move the tool preview
`LeftClick`	Confirms and commits the current position
`RightClick`	Aborts the placement and destroys the tool
`setModifierOne`	Toggles between fill mode and single-tile mode
`FindValidHitResult`	Validates and optionally transforms the cursor hit result (e.g., to apply grid snapping)
`ShowTool`	Moves the tool actor to the valid hit position
`ShowFillPolygon`	Detects the enclosed polygon from the node network and displays it
`ShowToolPolygon`	Displays the polygon defined by the tool’s `ToolShape` vector array

Tool shape

The tool shape is stored in a Vector array property called ToolShape. The default shape is a rectangle. To use a different shape, subclass the tool and set ToolShape in your BeginPlay override.

See Examples for a triangle tool example.

Single-tile mode vs. fill mode

Single-tile mode

The tool displays a fixed polygon (defined by ToolShape) around the cursor. On left-click, that polygon is committed at the cursor position.

Flow:

Tool receives CurrentMouseHitResults
FindValidHitResult validates the position
ShowToolPolygon renders the preview polygon
On left-click: send FFloorInputEvent with Kind = ClickPoint, ApplyMode = Commit
UClickPointResponsibilityHandler adds the polygon to UPolygonDatabase
UFloorPolygonChangeService notifies renderers

Fill mode

The tool detects the node network area enclosing the cursor and fills the entire enclosed polygon.

Flow:

Tool receives CurrentMouseHitResults
ShowFillPolygon calls the node network to find the enclosing polygon:
- Gets the enclosing UBasicNodeNetwork via UNodeNetworkSubsystem.getNodeNetworkEnclosingPosition
- Calls UBasicNodeNetwork.getFloorPolygonMeshDataEnclosingPosition to get the FFloorPolygon
Preview polygon is displayed
On left-click: send FFloorInputEvent with Kind = Fill, ApplyMode = Commit
UFillEventResponsibilityHandler processes the fill and writes to UPolygonDatabase

The FloorPlacementControllerComponent

FloorPlacementControllerComponent sits in the Player Controller and is the bridge between raw player input and the active tool.

Function	Description
`HandleLeftClick`	Validates the tool, collects objects under the cursor, calls the tool’s left-click handler. Destroys the tool if it is finished.
`HandleRightClick`	Forwards right-click to the tool
`HandleShift`	Forwards the modifier key to the tool (`setModifierOne`)
`SetActiveTool`	Assigns the currently active tool actor
`ActivateComponent`	Activates this component (enables input forwarding)
`DeactivateComponent`	Deactivates this component
`GetObjectsUnderMouseCursor`	Returns all hit objects under the cursor

Registering polygons: the PolygonDatabase

All committed floor polygons are stored in UPolygonDatabase. You can access it via:

Get Game Instance Subsystem → DynamicFloorPluginSubsystem → Get Polygon Database

Key operations:

Function	Description
`AddPolygon(Vertices, Height, MaterialId, FloorType)`	Adds a polygon, returns its `PolygonId`
`InsertPolygonWithMaterialHandling(Vertices, Holes, Height, MaterialId, FloorType)`	Adds a polygon with material-aware conflict handling
`RemovePolygonById(PolygonId)`	Removes a polygon by ID
`GetPolygonsInBox(Box2D, HeightLevel)`	Spatial query — returns polygons within a 2D bounding box
`EnterPreviewMode` / `ExitPreviewMode`	Toggle non-destructive preview state

How renderers receive updates

Once a polygon is written to the database, UFloorPolygonChangeService notifies all registered listeners:

Event	When it fires
`OnPolygonAdded(FFloorPolygon)`	A new polygon was committed
`OnPolygonRemoved(FFloorPolygon)`	A polygon was deleted
`OnPolygonUpdated(FFloorPolygon)`	A polygon was modified (not yet implemented in backend — reserved for future use)
`OnAllPolygonsTransferred`	End of a batch of changes — rebuild all meshes now