Sometimes the outline of a concave revoluted curved surface in axonometric projection would be complicated when there are some singular points on the outline.
在轴测投影中凹回转曲面的外形线可能存在尖点，这就使凹回转曲面的外形线变得复杂。
2
When calculating, only function of the longitudinal generating curve of the revoluted curved surface and the value of the projecting angle are needed to be substituted into these formulas.