切口、穿孔几何体的投影画法新探

New Disscussion of Projection Drawing in Cutting or Punching Geometric Substance

常见的几何体被切口、穿孔之后，其投影的画法都是在求出截交线的基础上完成的。而本文则从另一角度，把切口、穿孔看成是一整体，并称之为切除体，在求得切除体投影的基础上，完成切口。

Generally speaking,when geometric substance is cut off or punched,the way of projection drawing is usually finished on the basis of on the result of sectional crossing line.However,this article,from another point of view, takes cutting or punching as a whole,and calls it “the cutting part”. Based on getting the projection of the cutting part,the projection of geometric substance is finished after cutting or punching.