对圆的落影为椭圆时的曲线研究

Researching the Ellipse Curve of a Circle's Shadow

在求圆的落影时,若承影面垂直于圆所在的平面,则落影为一椭圆。在求该椭圆时,常用的方法为八点法。该方法的八个点不是椭圆的长短轴点,因此手工绘图的结果不精确,AutoCAD绘图时也不方便。本文通过对椭圆曲线的研究,对八点法提出了修正,寻找其椭圆的特征点,以精确和方便作图。

The shadow of a circle is an ellipse if the plane in which the circle lies is perpendicular to the projection plane. To get the ellipse curve, we usually adopt the eight-point-method. The paper rectifies the method after researching the shadow. Thus we can get it accurately and conveniently.