GameLib.D3.ComponentLookAt = function(
    componentId,
    targetEntity,
    targetOffset,
    rotationSpeed
) {
    this.componentId = componentId || GameLib.D3.Tools.RandomId();
    this.parentEntity = null;

    // Todo: this should be executed somewhere in game-lib-z, so that we don't execute it on every construction of an object.
    GameLib.D3.Utils.Extend(GameLib.D3.ComponentLookAt, GameLib.D3.ComponentInterface);

    // todo: USE TARGET OFFSET.
    this.targetEntity = targetEntity;

    if(GameLib.D3.Utils.UndefinedOrNull(targetOffset)) {
        targetOffset = new GameLib.D3.Vector3(0, 0, 0);
    }
    this.targetOffset = targetOffset;

    this.lastTargetQuaternion = new GameLib.D3.Vector4(0, 0, 0, 1);
    this.rotationSpeed = rotationSpeed || 22.0;
};


ComponentLookAt_currentPos = new THREE.Vector3();
ComponentLookAt_targetPos = new THREE.Vector3();
ComponentLookAt_upVector = new THREE.Vector3(0, 1, 0);
ComponentLookAt_parentQuaternion = new THREE.Quaternion(0, 0, 0, 1);
ComponentLookAt_tmpQuaternion = new THREE.Quaternion(0, 0, 0, 1);
ComponentLookAt_newRotationQuaternion = new THREE.Quaternion(0, 0, 0, 1);
ComponentLookAt_lastRotationQuaternion = new THREE.Quaternion(0, 0, 0, 1);
ComponentLookAt_lookAtMatrix = new THREE.Matrix4();

///////////////////////// Methods to override //////////////////////////
GameLib.D3.ComponentLookAt.prototype.onUpdate = function(
    deltaTime,
    parentEntity
) {
    if(this.targetEntity) {
        var target = this.targetEntity.position;

        ComponentLookAt_currentPos.set(
            parentEntity.position.x,
            parentEntity.position.y,
            parentEntity.position.z
        );

        ComponentLookAt_lastRotationQuaternion.set(
            this.lastTargetQuaternion.x,
            this.lastTargetQuaternion.y,
            this.lastTargetQuaternion.z,
            this.lastTargetQuaternion.w
        );

        ComponentLookAt_targetPos.set(
            target.x + this.targetOffset.x,
            target.y + this.targetOffset.y,
            target.z + this.targetOffset.z
        );

        ComponentLookAt_lookAtMatrix.lookAt(
            ComponentLookAt_currentPos,
            ComponentLookAt_targetPos,
            ComponentLookAt_upVector
        );

        ComponentLookAt_tmpQuaternion.setFromRotationMatrix(ComponentLookAt_lookAtMatrix);

        var t = deltaTime * this.rotationSpeed;
        t = t * t * t * (t * (6.0 * t - 15.0) + 10.0);

        THREE.Quaternion.slerp(ComponentLookAt_lastRotationQuaternion, ComponentLookAt_tmpQuaternion, ComponentLookAt_newRotationQuaternion, t);

        this.parentEntity.quaternion.x = this.lastTargetQuaternion.x = ComponentLookAt_newRotationQuaternion.x;
        this.parentEntity.quaternion.y = this.lastTargetQuaternion.y = ComponentLookAt_newRotationQuaternion.y;
        this.parentEntity.quaternion.z = this.lastTargetQuaternion.z = ComponentLookAt_newRotationQuaternion.z;
        this.parentEntity.quaternion.w = this.lastTargetQuaternion.w = ComponentLookAt_newRotationQuaternion.w;
    }
};