使用UF函数可以获取圆弧边或圆弧线中心点和半径:

1.使用 UF_CURVE_ask_arc_data:

 theUf.Curve.AskArcData(edge.Tag, out UFCurve.Arc arc);
 theUf.Curve.CreateArc(ref arc, out Tag arc_tag);

 double[] matrix_values = new double[9];
 double[] vec_product = new double[3];
 theUf.Csys.AskMatrixValues(arc.matrix_tag, matrix_values);
 theUf.Mtx3.VecMultiply(arc.arc_center, matrix_values, vec_product);

2.使用 UF_EVAL_ask_arc:

 uf.Eval.Initialize(iEdge.Tag, out var evaluator);
 uf.Eval.IsArc(evaluator, out var isArc);
 if (isArc)
 {
   uf.Eval.AskArc(evaluator, out var arc);
   center = arc.center.ToPoint3d();
   radius = arc.radius;
 }
 else
 {
   uf.Eval.AskEllipse(evaluator, out var ellipse);
   center = ellipse.center.ToPoint3d();
   radius = ellipse.minor;
 }