UseableStructure — Building Placement

Advanced45-60 minutesWindowsVisual StudioU3 SDK

UseableStructure is the placement engine for structure items in Unturned. Unlike UseableBarricade with its 15+ bespoke placement strategies, UseableStructure delegates entirely to UseableHousingUtils — a unified grid-based placement system built around housing connection validation. The class manages foundation height offsets, rotation presets, client-side preview with green/red highlighting, server-authoritative validation via EHousingPlacementResult, and an animation-timed construct cycle with sound and alert triggers.

Source code location: Unturned/Useable/UseableStructure.cs

Architecture Overview

UseableStructure extends Useable and relies on UseableHousingUtils for all placement logic. The class uses 14 private fields to track its state machine across the equip → preview → validate → animate → spawn lifecycle. Key architectural components:

• placementPreviewTransform: Stripped-down preview ghost for visual placement feedback.
• UseableHousingUtils.ValidatePendingPlacement: Server-authoritative grid validation.
• UseableHousingUtils.FindPlacement: Client-side placement projection.
• Housing connection system: Grid-snapped placement enforced by HousingConnections.

Equip and Preview

Preview Creation

if (channel.IsLocalPlayer)
{
    isPlacementPreviewValid = false;
    placementPreviewTransform = UseableHousingUtils.InstantiatePlacementPreview(equippedStructureAsset);
}

The preview is highlighted green/red based on validity via HighlighterTool.help().

Field Layout

UseableStructure uses 14 private fields:

Field	Type	Purpose
placementPreviewTransform	Transform	Ghost preview object
isPlacementPreviewValid	bool	Current highlight state
useAnimationStartTime	double	Time.timeAsDouble at animation start
useAnimationDuration	float	Length of "Use" clip
isWaitingForSoundTrigger	bool	Sound hasn't fired yet
isUseAnimationPlaying	bool	Animation in progress
hasServerReceivedBuildRequest	bool	Server received RPC
isServerBuildRequestInitiallyApproved	bool	Pre-validation result
pendingPlacementPosition	Vector3	Computed placement point
pendingPlacementYaw	float	Computed rotation
animatedRotationOffset	float	Lerp-smoothed offset
customRotationOffset	float	Player rotation input
foundationPositionOffset	float	Scroll wheel height
serverPlacementPosition / serverPlacementYaw	Vector3 / float	Server-side copies

Update Loop — tick()

if (!isUseAnimationPlaying)
{
    bool isPlacementValid = UpdatePendingPlacement();
    if (isPlacementPreviewValid != isPlacementValid)
    {
        isPlacementPreviewValid = isPlacementValid;
        HighlighterTool.help(placementPreviewTransform, isPlacementPreviewValid);
    }
}

Foundation Height Offset

Scroll wheel adjusts foundation height:

foundationPositionOffset = Mathf.Clamp(
    foundationPositionOffset + (scrollWheelInput * FOUNDATION_MOUSE_SCROLL_MULTIPLIER),
    FOUNDATION_MIN_OFFSET, FOUNDATION_MAX_OFFSET);

Rotation System

Secondary input rotates via presets based on EConstruct:

if (equippedStructureAsset.construct == EConstruct.FLOOR || ...)
    delta = 90.0f;
else if (equippedStructureAsset.construct == EConstruct.RAMPART || ...)
    delta = 180.0f;
else
    delta = 30.0f;

if (InputEx.GetKey(KeyCode.LeftShift))
    delta *= -1.0f;
customRotationOffset += delta;

The animatedRotationOffset interpolates toward customRotationOffset using Mathf.Lerp for smooth visual rotation.

Placement Flow — startPrimary()

public override bool startPrimary()
{
    if (Dedicator.IsDedicatedServer ? isServerBuildRequestInitiallyApproved : UpdatePendingPlacement())
    {
        if (channel.IsLocalPlayer)
            SendBuildStructure.Invoke(GetNetId(), ENetReliability.Reliable,
                pendingPlacementPosition, pendingPlacementYaw + customRotationOffset);
        player.equipment.isBusy = true;
        PlayUseAnimation();
        if (Provider.isServer)
            SendPlayConstruct.Invoke(GetNetId(), ENetReliability.Unreliable,
                channel.GatherRemoteClientConnectionsExcludingOwner());
    }
}

The SendPlayConstruct RPC broadcasts the construct animation to other clients for visual syncing.

Client-Side Placement Projection — UpdatePendingPlacement

private bool UpdatePendingPlacement()
{
    if (!UseableHousingUtils.FindPlacement(equippedStructureAsset, player,
        customRotationOffset, foundationPositionOffset,
        out pendingPlacementPosition, out pendingPlacementYaw))
        return false;

    if (!UseableHousingUtils.IsPendingPositionValid(player, pendingPlacementPosition))
        return false;

    return true;
}

Server Validation — ReceiveBuildStructure

if ((newPoint - player.look.aim.position).sqrMagnitude < HousingConnections.MAX_PLACEMENT_SQR_DISTANCE)
{
    serverPlacementPosition = newPoint;
    serverPlacementYaw = newAngle;
    if (!UseableHousingUtils.IsPendingPositionValid(player, serverPlacementPosition))
        isServerBuildRequestInitiallyApproved = false;
    else
    {
        string obstructionHint = null;
        EHousingPlacementResult result = UseableHousingUtils.ValidatePendingPlacement(
            equippedStructureAsset, ref serverPlacementPosition,
            serverPlacementYaw, ref obstructionHint);
        isServerBuildRequestInitiallyApproved = (result == EHousingPlacementResult.Success);
    }
}

Finalize — simulate()

After the use animation completes, simulate() double-checks validity and spawns:

if (!UseableHousingUtils.IsPendingPositionValid(player, serverPlacementPosition))
{
    player.equipment.dequip();
}
else
{
    EHousingPlacementResult result = UseableHousingUtils.ValidatePendingPlacement(
        equippedStructureAsset, ref serverPlacementPosition,
        serverPlacementYaw, ref obstructionHint);
    if (result != EHousingPlacementResult.Success)
        player.equipment.dequip();
    else
    {
        StructureManager.dropStructure(
            new Structure(asset, asset.health),
            serverPlacementPosition, 0, serverPlacementYaw, 0,
            channel.owner.playerID.steamID.m_SteamID,
            player.quests.groupID.m_SteamID);
        player.equipment.use();
    }
}

The double-validation pattern (client pre-check + server authoritative check) prevents race conditions and hacked clients.

Sound and Alert

Sound playback at 80% through the animation:

if (isWaitingForSoundTrigger && HasReachedSoundTrigger)
{
    isWaitingForSoundTrigger = false;
    if (!Dedicator.IsDedicatedServer)
        player.playSound(equippedStructureAsset.use);
    if (Provider.isServer)
        AlertTool.alert(transform.position, 8);
}

The 8-meter alert radius notifies nearby zombies of building activity.

Housing Connection Validation

UseableHousingUtils.ValidatePendingPlacement performs:

1. Pillar connection check — Must connect to at least one existing pillar or foundation.
2. Overlap check — No existing structure occupies the same grid space.
3. Terrain clearance — Footprint not blocked by terrain.
4. Clip volume check — Rejects no-build volumes.
5. Safezone check — Rejects safezones unless explicitly allowed.

Key Design Insights

1. Delegated placement — UseableStructure delegates entirely to UseableHousingUtils, a clean contrast to UseableBarricade's monolithic approach.
2. Double validation — Client pre-check + server authoritative re-check prevents desync.
3. Animation-timed state machine — Sound triggers at 80%, spawn finalizes at 100%, ensuring proper visual sequencing.
4. Rotation presets — Ramparts rotate 180°, floors 90°, others 30° — appropriate scale per construct type.
5. Foundation offset — Scroll wheel adjusts height, perpendicular to player look direction for intuitive control.
6. Alert integration — AlertTool.alert(8) makes building a noisy activity that attracts nearby AI.

Document history