Building Build Component

UBuildingBuildComponent is the primary entry point for local building interactions. It is responsible for:

• Build Mode
• Building previews
• Building selection and editing
• Rotation and position adjustments
• Socket snapping
• Cost evaluation for UI
• Default building UI

This component is typically added to a player-controlled Pawn or Character.

Note

Building creation, movement, and removal should be initiated through UBuildingBuildComponent.

Final placement validation and Entity modifications are performed by the server.

Basic Information

Item	Description
Class	UBuildingBuildComponent
Base Class	UActorComponent
Recommended Owner	Player-controlled Pawn or Character
Primary Purpose	Local building interaction and preview control
Blueprint Support	Supported
Server Validation	Handled by the building world system
Default UI	Can be created and managed automatically by the plugin

Basic Workflow

Toggle Build Mode
→ Start Build
→ Adjust position, rotation, or snap point
→ Confirm Build

Build States

EBuildState represents the component's current build state.

State	Description
Idle	Build Mode is disabled.
Ready	Build Mode is active, but no operation is currently in progress.
Build	A new building is being placed.
Edit	An existing building is being edited.

Common state transitions:

Idle → Ready
Enter Build Mode

Ready → Build
Start placing a new building

Ready → Edit
Start editing an existing building

Build / Edit → Ready
Complete or cancel the current operation

Any active state → Idle
Exit Build Mode

Build Mode APIs

API	Description
ToggleBuildMode	Toggles Build Mode.
EnterBuild	Enters Build Mode.
ExitBuild	Completely exits Build Mode.
CancelBuild	Cancels the current operation and returns to Ready.
GetCurrentBuildState	Returns the current build state.
IsInBuildMode	Checks whether Build Mode is active.
HasActiveBuildOperation	Checks whether a building is currently being placed or edited.

ToggleBuildMode

Toggles Build Mode.

UFUNCTION(BlueprintCallable, Category = "Building|Mode")
void ToggleBuildMode();

If the current state is Idle, the component enters Build Mode. Otherwise, it exits Build Mode.

EnterBuild

Enters Build Mode without immediately placing a building.

UFUNCTION(BlueprintCallable, Category = "Building|Mode")
void EnterBuild();

After this function is called, the state changes to Ready.

ExitBuild

Completely exits Build Mode.

UFUNCTION(BlueprintCallable, Category = "Building|Mode")
void ExitBuild();

This function clears the current preview, selection, and editing state, then changes the state to Idle.

CancelBuild

Cancels the current placement or editing operation.

UFUNCTION(BlueprintCallable, Category = "Building|Mode")
void CancelBuild();

The component remains in Build Mode, and the state returns to Ready.

GetCurrentBuildState

Returns the current build state.

UFUNCTION(BlueprintPure, Category = "Building|Mode")
EBuildState GetCurrentBuildState() const;

Type	Data Type	Description
Return	EBuildState	The current build state.

IsInBuildMode

Checks whether Build Mode is active.

UFUNCTION(BlueprintPure, Category = "Building|Mode")
bool IsInBuildMode() const;

Type	Data Type	Description
Return	bool	Returns true when the current state is not Idle.

HasActiveBuildOperation

Checks whether an active building operation exists.

UFUNCTION(BlueprintPure, Category = "Building|Mode")
bool HasActiveBuildOperation() const;

Type	Data Type	Description
Return	bool	Returns true when the current state is Build or Edit.

Building Operation APIs

API	Description
StartBuild	Starts placing a new building.
RotateBuild	Rotates the current building preview.
AdjustBuildHeight	Adjusts the building preview height.
AdjustBuildDistance	Adjusts the building preview distance.
ConfirmBuild	Confirms the current operation.
DeleteBuild	Removes the building currently being edited.
StartEditBuild	Starts editing the currently highlighted building.
GetCurrentOperationEntityId	Returns the Entity ID currently being edited.
GetCurrentBuildingData	Returns the building data used by the current operation.

StartBuild

Starts placing the specified building.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void StartBuild(
    UBuildingDataAsset* Data
);

Type	Name	Data Type	Description
Param	Data	UBuildingDataAsset*	The building data asset to place.

After this function is called, the component creates a building preview and enters the Build state.

RotateBuild

Rotates the current building preview.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void RotateBuild(
    float YawDelta
);

Type	Name	Data Type	Description
Param	YawDelta	float	The Yaw angle added by this operation.

For example, to rotate by 90 degrees each time:

Yaw Delta = 90

AdjustBuildHeight

Adjusts the height offset of the current building preview.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void AdjustBuildHeight(
    float HeightDelta
);

Type	Name	Data Type	Description
Param	HeightDelta	float	The amount of height added or removed by this operation.

A positive value moves the preview upward, while a negative value moves it downward.

AdjustBuildDistance

Adjusts the distance between the building preview and the component's Owner.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void AdjustBuildDistance(
    float InputValue
);

Type	Name	Data Type	Description
Param	InputValue	float	The adjustment direction, typically -1 or 1.

The actual distance adjustment is:

Input Value × Build Distance Step

Input Value	Result
1	Moves the preview farther away.
-1	Moves the preview closer.

Build Distance Step is configured in the plugin settings.

ConfirmBuild

Confirms the current operation.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void ConfirmBuild();

The behavior depends on the current state:

Current State	Behavior
Build	Submits a request to place a new building.
Edit	Submits the updated building position.
Ready	Processes the current building selection.

Final position validation, cost consumption, and Entity modifications are performed by the server.

DeleteBuild

Removes the building currently being edited.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void DeleteBuild();

This function only takes effect when a valid Edit operation exists.

StartEditBuild

Starts editing the currently highlighted building.

UFUNCTION(BlueprintCallable, Category = "Building|Operation")
void StartEditBuild();

If successful, the component enters the Edit state and creates an editing preview.

GetCurrentOperationEntityId

Returns the Entity ID of the building currently being edited.

UFUNCTION(BlueprintPure, Category = "Building|Operation")
int32 GetCurrentOperationEntityId() const;

Type	Data Type	Description
Return	int32	The current Entity ID, or INDEX_NONE when no valid target exists.

GetCurrentBuildingData

Returns the building data used by the current operation.

UFUNCTION(BlueprintPure, Category = "Building|Operation")
UBuildingDataAsset* GetCurrentBuildingData() const;

Type	Data Type	Description
Return	UBuildingDataAsset*	The current building data, or possibly nullptr when no operation is active.

Building Evaluation APIs

EvaluateBuildForUI

Evaluates building costs and construction requirements for UI display.

UFUNCTION(BlueprintCallable, Category = "Building|Evaluation")
FBuildingBuildCheckResult EvaluateBuildForUI(
    const UBuildingDataAsset* BuildingData,
    const FTransform& PreviewTransform
) const;

Type	Name	Data Type	Description
Param	BuildingData	const UBuildingDataAsset*	The building data to evaluate.
Param	PreviewTransform	const FTransform&	The world transform of the building preview.
Return	CheckResult	FBuildingBuildCheckResult	Cost and failure information.

This function is used only for UI evaluation and does not consume resources.

Owner APIs

GetOwningController

Returns the Controller associated with the Pawn that owns this component.

UFUNCTION(BlueprintPure, Category = "Building|Owner")
AController* GetOwningController() const;

Type	Data Type	Description
Return	AController*	The Owner Pawn's Controller, or nullptr if unavailable.

Aiming APIs

EBuildingAimMode determines the origin of the building trace.

Mode	Description
CameraCenter	Traces from the camera or the center of the screen.
MouseCursor	Traces from the mouse cursor position.

SetBuildingAimMode

Changes the current aiming mode.

UFUNCTION(BlueprintCallable, Category = "Building|Aim")
void SetBuildingAimMode(
    EBuildingAimMode NewAimMode
);

Type	Name	Data Type	Description
Param	NewAimMode	EBuildingAimMode	The new aiming mode.

GetBuildingAimMode

Returns the current aiming mode.

UFUNCTION(BlueprintPure, Category = "Building|Aim")
EBuildingAimMode GetBuildingAimMode() const;

Type	Data Type	Description
Return	EBuildingAimMode	The current aiming mode.

The default value is loaded from the plugin settings when the component is initialized.

Snap Candidate APIs

API	Description
SelectNextSnapPoint	Selects the next snap candidate.
SelectPreviousSnapPoint	Selects the previous snap candidate.
GetSnapCandidateCount	Returns the current number of candidates.
GetActiveSnapCandidateIndex	Returns the current candidate index.
ToggleSnapActive	Enables or disables Socket snapping.
GetSnapActiveState	Returns whether snapping is currently enabled.

SelectNextSnapPoint

Selects the next compatible snap candidate.

UFUNCTION(BlueprintCallable, Category = "Building|Snap")
bool SelectNextSnapPoint();

Type	Data Type	Description
Return	bool	Returns true when a candidate is selected successfully.

This function prioritizes the current cache and does not actively perform a new area search.

SelectPreviousSnapPoint

Selects the previous compatible snap candidate.

UFUNCTION(BlueprintCallable, Category = "Building|Snap")
bool SelectPreviousSnapPoint();

Type	Data Type	Description
Return	bool	Returns true when a candidate is selected successfully.

GetSnapCandidateCount

Returns the number of currently cached snap candidates.

UFUNCTION(BlueprintPure, Category = "Building|Snap")
int32 GetSnapCandidateCount() const;

Type	Data Type	Description
Return	int32	The current number of candidates.

GetActiveSnapCandidateIndex

Returns the index of the currently selected candidate.

UFUNCTION(BlueprintPure, Category = "Building|Snap")
int32 GetActiveSnapCandidateIndex() const;

Type	Data Type	Description
Return	int32	The current index, or INDEX_NONE when not snapped.

ToggleSnapActive

Enables or disables Socket snapping for the current component.

UFUNCTION(BlueprintCallable, Category = "Building|Snap")
void ToggleSnapActive();

When disabled, the building preview does not automatically apply Socket snapping.

Call this function again to re-enable snapping.

GetSnapActiveState

Returns whether snapping is currently enabled.

UFUNCTION(BlueprintPure, Category = "Building|Snap")
bool GetSnapActiveState() const;

Type	Data Type	Description
Return	bool	Returns true when snapping is enabled.

For snapping configuration, see Snapping System.

Events

Event	Description
OnBuildingCheck	Triggered when the Ghost performs a placement validation check.
OnBuildingSelected	Triggered when the selected building data changes.
OnBuildStateChanged	Triggered when the build state changes.

OnBuildingCheck

Triggered when the building preview performs a placement validation check.

UPROPERTY(BlueprintAssignable, Category = "Building|Events")
FOnBuildingCheck OnBuildingCheck;

Delegate declaration:

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(
    FOnBuildingCheck,
    FGhostCheckResultContext,
    Context
);

Type	Name	Data Type	Description
Param	Context	FGhostCheckResultContext	The current Ghost validation result.

This event can be used to update:

• Placement availability indicators
• Failure reasons
• Building preview UI
• Custom validation messages

OnBuildingSelected

Triggered when the currently selected building data changes.

UPROPERTY(BlueprintAssignable, Category = "Building|Events")
FOnBuildingSelected OnBuildingSelected;

Delegate declaration:

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(
    FOnBuildingSelected,
    UBuildingDataAsset*,
    Data
);

Type	Name	Data Type	Description
Param	Data	UBuildingDataAsset*	The currently selected building data.

This event can be used to update building details, cost information, or selection UI.

OnBuildStateChanged

Triggered when the build state changes.

UPROPERTY(BlueprintAssignable, Category = "Building|Events")
FOnBuildStateChanged OnBuildStateChanged;

Delegate declaration:

DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(
    FOnBuildStateChanged,
    EBuildState,
    PreviousState,
    EBuildState,
    NewState
);

Type	Name	Data Type	Description
Param	PreviousState	EBuildState	The state before the change.
Param	NewState	EBuildState	The state after the change.

This event can be used to:

• Show or hide the building UI
• Switch input mappings
• Update operation prompts
• Determine whether an operation was completed or canceled

Default UI

When UI Handling Mode in the project settings is set to Use Default, the component automatically manages the default building interface.

State	Default UI Behavior
Idle	Hides the building interface.
Ready	Displays the building selection interface.
Build	Displays building placement information.
Edit	Displays building editing information.

Projects generally only need to call:

Toggle Build Mode

When using a custom UI, listen to:

On Building Check
On Building Selected
On Build State Changed

For UI configuration, see Plugin Settings.

Multiplayer

Operation	Execution Location
Input handling	Local player
Ghost Preview	Local player
Snap candidate calculation	Local player
Cost evaluation for UI	Local player
Building request submission	Local player
Final position validation	Server
Resource consumption	Server
Entity creation, movement, and removal	Server
Building result synchronization	Plugin networking system

UBuildingBuildComponent handles local interactions but does not bypass server-authoritative validation.

Recommended Input Mappings

Input	Recommended API
Toggle Build Mode	ToggleBuildMode
Confirm	ConfirmBuild
Cancel	CancelBuild
Rotate	RotateBuild
Adjust height	AdjustBuildHeight
Adjust distance	AdjustBuildDistance
Next snap point	SelectNextSnapPoint
Previous snap point	SelectPreviousSnapPoint
Enable or disable snapping	ToggleSnapActive
Remove building	DeleteBuild
Start editing	StartEditBuild

Troubleshooting

Issue	What to Check
Unable to enter Build Mode	Check whether the component is attached to the local player's Pawn.
StartBuild does not create a preview	Check the Building Data Asset and Preview Mesh.
ConfirmBuild does not create a building	Check Ghost validity, building costs, and the server request.
Unable to select a building	Check the building selection collision channel.
Unable to enter the editing state	Check whether a valid building is highlighted.
Rotation has no effect	Check whether an active building preview exists.
Unable to find snap points	Check the snapping state, collision channels, and Snap configuration.
Unable to switch snap points	Check whether multiple compatible candidates exist.
Default UI is not displayed	Check UI Handling Mode and Build Widget Class.
Custom UI does not update	Check whether the relevant events are bound correctly.
Client operations do not respond	Check the Request Actor and server connection.

Related Documentation

• Plugin Settings
• Collision Configuration
• Building Data Assets
• Snapping System
• Building Cost System