/// <summary>
/// 三点绘制圆弧
/// </summary>
/// <param name="db">图形数据库</param>
/// <param name="startPoint3d">起点坐标</param>
/// <param name="pointOnArc">圆弧上的点</param>
/// <param name="endPoint3d">重点坐标</param>
/// <returns></returns>
public static ObjectId AddArcToModelSpace(this Database db, Point3d startPoint3d, Point3d pointOnArc, Point3d endPoint3d)
{
//判断三点是否在同一条直线上
if (startPoint3d.IsOnOneLine(pointOnArc, endPoint3d))
{
Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
ed.WriteMessage("3个顶点在同一条直线上，无法绘制圆弧");
return(ObjectId.Null);
}
//创建几何对象
CircularArc3d CArc = new CircularArc3d(startPoint3d, pointOnArc, endPoint3d);
//获取几何对象的属性
double radius = CArc.Radius; //半径
Point3d conter = CArc.Center; //圆心
//Vector3d cs = conter.GetVectorTo(startPoint3d);//圆心与第一个点构成向量
//Vector3d ce = conter.GetVectorTo(endPoint3d);//圆心与第二个点构成向量
//Vector3d xVector = new Vector3d(1, 0, 0);//X正方向的向量
////获取角度
//double startAngle = cs.Y>0 ? xVector.GetAngleTo(cs): -xVector.GetAngleTo(cs);//圆心与第一个点的角度
//double endAngle = ce.Y>0 ? xVector.GetAngleTo(ce): -xVector.GetAngleTo(ce);//圆心与第二个点的角度
//获取角度
double startAngle = conter.GetAngle(startPoint3d);
double endAngle = conter.GetAngle(endPoint3d);
//创建圆弧对象
Arc arc = new Arc(conter, radius, startAngle, endAngle);
return(AddEntityToModelSpace(db, arc));//添加到图形数据库中
}
/// <summary>
/// 根据圆心、起点、角度绘制圆弧
/// </summary>
/// <param name="db">图形数据库</param>
/// <param name="center">圆心</param>
/// <param name="startPoint3d">起点</param>
/// <param name="degree">夹角值(角度值)</param>
/// <returns></returns>
public static ObjectId AddArcToModelSpace(this Database db, Point3d center, Point3d startPoint3d, double degree)
{
//获取半径
double radius = center.GetDistanceBetweenToPoint(startPoint3d);
//获取起始角度
double startAngle = center.GetAngle(startPoint3d);
//声明圆弧对象 //角度转换为弧度
Arc arc = new Arc(center, radius, startAngle, startAngle + degree.DegreeToAngle());
//添加到图形数据库中
return(AddEntityToModelSpace(db, arc));
}