expandByScalar( scalar ) {

		this.min.addScalar( - scalar );
		this.max.addScalar( scalar );

		return this;

	}
Expands each dimension of the box by the given scalar. If negative, the
dimensions of the box will be contracted.

@param {number} scalar - The scalar value that should expand the bounding box.
@return {Box3} A reference to this bounding box.