凹回转面可见轮廓线投影图中奇点的分析

THE ANALYSES OF SINGULAR POINTS IN THE PROJECTION OF THE OUTLINE OF CONCAVE SURFACE OF REVOLUTION

本文从理论上对凹回转面可见轮廓线正投影图中出现的奇点进行了分析，并对奇点在什么情况下是可见轮廓线投影图中的尖点的情况进行了讨论，推导出凹回转面可见轮廓线的投影在奇点附近光滑的条件，同时对凹回转面可见轮廓线斜投影图中的情况作了研究，为计算机绘画凹回转面的投影图提供了一个准确的数学模型。

The singular point appearing in the orthogonal projection of the outline of concave rotative surface is analysed in the paper. The condition to be smooth near the singular point for the projection of outline of concave rotative surface is denied after the singular point whether it is the sharp point of the projection of the outline is discussed. The state in the oblique projection of concave rotative surface is studied also, and an accurate mathematical model f-or the projection of concave rotative surface drawn by computer is gived in the article.