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vecad控件中添加样条曲线需要使用到三个函数:
AddVertex、ClearVertices、AddPolyline
在创建样条曲线前需要将样式曲线的各个节点用AddVertex依次添加，然后用AddPolyline创建样条曲线：
Vecad1.AddVertex 0, 0, 0
Vecad1.AddVertex 2, 2, 0
Vecad1.AddVertex 10, 10, 0
Vecad1.AddVertex 15, 6, 0
Vecad1.AddVertex 10, 3, 0
Vecad1.AddVertex 20, 1, 0
Vecad1.AddPolyline CAD_PLINE_ROUND, 0
Vecad1.Update
在创建下一条曲线前需要用ClearVertices清空顶点列表：
Vecad1.ClearVertices
Vecad1.AddVertex 0, 0, 0
Vecad1.AddVertex 2, 2, 0
Vecad1.AddVertex 10, 10, 0
Vecad1.AddVertex 15, 6, 0
Vecad1.AddVertex 10, 3, 0
Vecad1.AddVertex 20, 1, 0
Vecad1.AddPolyline CAD_PLINE_SPLINE, 0
Vecad1.Update
AddPolyline第一个参数的取值见下表：
| Value | Fit type |
|---|---|
| CAD_PLINE_LINEAR | Direct lines or arcs between vertices. |
| CAD_PLINE_QUAD | Quadratic B-spline. |
| CAD_PLINE_CUBIC | Cubic B-spline. |
| CAD_PLINE_BEZIER | Bezier curve. |
| CAD_PLINE_SPLINE | Cubic spline goes through vertices. |
| CAD_PLINE_ROUND | Cubic spline goes through vertices. |
| CAD_PLINE_LINQUAD | Combination of linear segments and quadratic B-spline segments. |
不同参数的效果请自行实验。