如何获取两条直线的交点？

家在湾里 · 发表于 2011-3-24 22:05:00

如何获取两条直线的交点？有什么函数吗？还有，对多段线进行内部填充时多段线必须是封闭的吗？

sieben · 发表于 2011-3-24 23:29:00

public virtual void IntersectWith(Autodesk.AutoCAD.DatabaseServices.Entity entityPointer, Autodesk.AutoCAD.DatabaseServices.Intersect intersectType, Autodesk.AutoCAD.Geometry.Point3dCollection points, int thisGraphicSystemMarker, int otherGraphicSystemMarker)
Autodesk.AutoCAD.DatabaseServices.Entity 的成员
public virtual void IntersectWith(Autodesk.AutoCAD.DatabaseServices.Entity entityPointer, Autodesk.AutoCAD.DatabaseServices.Intersect intersectType, Autodesk.AutoCAD.Geometry.Plane projectionPlane, Autodesk.AutoCAD.Geometry.Point3dCollection points, int thisGraphicSystemMarker, int otherGraphicSystemMarker)
Autodesk.AutoCAD.DatabaseServices.Entity 的成员

sieben · 发表于 2011-3-24 23:31:00

是要求曲线组成一个封闭区域，若是一个多义线则要求多义线是封闭的，也可以多个不封闭的多义线相连成一个封闭轮廓。

家在湾里 · 发表于 2011-3-29 09:56:00

回复
这两个函数好难看懂啊！那我也可以写一个方法来求线段的交点吧？

cdinten · 发表于 2011-3-29 10:33:00

http://379910987.blog.163.com/bl ... 972010111612020453/

sieben · 发表于 2011-3-29 12:01:00

呵呵，当然，所有的函数都是人写出来的，别人可以，当然你也可以！
下面是个示意，希望能帮到你。
///
/// 求两条曲线的交点,本函数为应对Polyline.IntersectWith函数的Bug
/// Vrsion : 2009.02.10 Sieben
/// Vrsion : 2010.12.25 增加判断输入实体是否为平面实体
///
///
///
///
public static Point3dCollection IntersectWith(Entity ent1, Entity ent2, Intersect intersectType)
{
   try
   {
      if (ent1 is Polyline || ent2 is Polyline)
      {
      if (ent1 is Polyline && ent2 is Polyline)
      {
         Polyline pline1 = (Polyline)ent1;
         Polyline pline2 = (Polyline)ent2;
         return IntersectWith(pline1.ConvertTo(false), pline2.ConvertTo(false), intersectType);
      }
      else if (ent1 is Polyline)
      {
         Polyline pline1 = (Polyline)ent1;
         return IntersectWith(pline1.ConvertTo(false), ent2, intersectType);
      }
      else
      {
         Polyline pline2 = (Polyline)ent2;
         return IntersectWith(ent1, pline2.ConvertTo(false), intersectType);
      }
      }
      else
      {
      Point3dCollection interPs = new Point3dCollection();
      if (ent1.IsPlanar && ent2.IsPlanar)
         ent1.IntersectWith(ent2, intersectType, new Plane(Point3d.Origin, Vector3d.ZAxis), interPs, 0, 0);
      else
         ent1.IntersectWith(ent2, intersectType, interPs, 0, 0);
      return interPs;
      }
   }
   catch (System.Exception ex)
   {
      return null;
   }
}

sieben · 发表于 2011-3-29 12:08:00

///
/// 求两两连线的交点
///
/// 第一组点
/// 第一组点
/// 第二组点
/// 第二组点
/// 若有交点就返回交点，否则返回P11
static public Point3d PLL(Point3d P11, Point3d P12, Point3d P21, Point3d P22)
{
   double A1 = P12.Y - P11.Y;
   double B1 = P11.X - P12.X;
   double C1 = -A1 * P11.X - B1 * P11.Y;
   double A2 = P22.Y - P21.Y;
   double B2 = P21.X - P22.X;
   double C2 = -A2 * P21.X - B2 * P21.Y;
   double dlt = A1 * B2 - A2 * B1;
   double dltx = C1 * B2 - C2 * B1;
   double dlty = A1 * C2 - A2 * C1;
   if (Math.Abs(dlt) < 0.00000001)
   {
      return P11;
   }
   else
   {
      return new Point3d(-1.0 * (dltx / dlt), -1.0 * (dlty / dlt), 0);
   }
}
注意，直线的交点和直线段的交点是有区别的