| 摘要 |
In one aspect, a computer aided design (CAD) system is disclosed that includes a user interface comprising means for updating a current reference point for specifying a plurality of coordinate positions indicating endpoints of a plurality of graphical objects. The user interface can accept successive coordinate positions corresponding to the endpoints from a user, wherein any two endpoints define a direction. Upon specification of a new endpoint, the updating means updates the current reference point to be a penultimate endpoint if the new endpoint and the penultimate endpoint define a new direction. And if the new endpoint and the penultimate endpoint define the same direction as a current direction, the updating means maintains the current reference point (i.e., it does not change the current reference point).
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