select( startPoint, endPoint ) {

		this.startPoint = startPoint || this.startPoint;
		this.endPoint = endPoint || this.endPoint;
		this.collection = [];

		this._updateFrustum( this.startPoint, this.endPoint );
		this._searchChildInFrustum( _frustum, this.scene );

		return this.collection;

	}
This method selects 3D objects in the scene based on the given start
and end point. If no parameters are provided, the method uses the start
and end values of the respective members.

@param {Vector3} [startPoint] - The start point.
@param {Vector3} [endPoint] - The end point.
@return {Array<Object3D>} The selected 3D objects.