直线投影到三角网曲面上

civil 3d中要素线及放坡相关的.net api基本没有开放，

com api也只有要素线有有限的一些功能，

有时需要要素线到曲面的投影线，

这把我卡了很长时间。

 

今天想到了曲面有获取点到曲面投影的功能，

所以利用这个功能，

实现了求取直线到曲面投影的方法。

基本的思路是：

直线起点投影到曲面，

通过投影点获取到相应的三角形，

之后直线投影到三角形所在的平面，

再求投影线与三角形的交点，

通过交线找到三角形的边（有待优化），

通过三角形的边找到下一个三角形，

循环操作，

找出每一交点，

连成三维多段线。

主要的代码如下，

还不完善，

有需要的朋友可以借鉴一下，

拿去继续优化。

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/// <summary> /// 2020年10月31日17:00:18 /// 直线投影到三角网曲面 /// </summary> /// <param name="l">直线</param> /// <param name="sur">曲面</param> /// <param name="direction">投影方向</param> /// <returns>投影三维多段线</returns> public static Polyline3d ProjectToTinsurface(this Line l, TinSurface sur, Vector3d direction) {     Point3dCollection pts = new Point3dCollection();     Point3d projectedPt01 = sur.GetIntersectionPoint(l.StartPoint, direction);     Point3d projectedPt02 = sur.GetIntersectionPoint(l.EndPoint, direction);       pts.Add(projectedPt01);       var seedTriangle = sur.FindTriangleAtXY(projectedPt01.X, projectedPt01.Y);     var projectedLine = l.GetProjectedCurve(seedTriangle.Plane(), direction) as Line;     var intersectPts = projectedLine.GetIntersectPoints(seedTriangle);     Point3d seedPt = new Point3d();     // 如果三角形很大，直线很短，两个点投影后落到一个三角形内时，     // 交点数为0，需要直接跳过     // 交点数大于0时，说明与三角形的边有交点     if (intersectPts.Count > 0)     {         foreach (Point3d pt in intersectPts)         {             if (!pts.Contains(pt))             {                 seedPt = pt;                 pts.Add(pt);             }         }         // 执行do while循环，依次选择相邻的三角形，依次查找交点         do         {             // 交点位置的边             // 这个应该有优化的空间，在求交点是记录边，             // 之后传递到这里，而不是再用点查找一遍             var edge = sur.FindEdgeAtXY(seedPt.X, seedPt.Y);             // 选择下一个三角形             if (edge.Triangle1.GetHashCode() != seedTriangle.GetHashCode())             {                 seedTriangle = edge.Triangle1;             }             else             {                 seedTriangle = edge.Triangle2;             }             // 投影直线到三角形上             projectedLine = l.GetProjectedCurve(seedTriangle.Plane(), direction) as Line;             // 获取投影线与三角形的交点             intersectPts = projectedLine.GetIntersectPoints(seedTriangle);             // 如果交点不在交点集合中，添加到集合             foreach (Point3d pt in intersectPts)             {                 if (!pts.Contains(pt))                 {                     seedPt = pt;                     pts.Add(pt);                 }             }         } while (intersectPts.Count > 1);     }     // 添加终点投影点到集合中     pts.Add(projectedPt02);     // 生成三维多段线     return new Polyline3d(Poly3dType.SimplePoly, pts, false); } /// <summary> /// 2020年10月31日17:07:38 /// 三角形平面 /// 获取曲面三角形所在的平面 /// </summary> /// <param name="triangle">三角形</param> /// <returns>平面</returns> public static Plane Plane(this TinSurfaceTriangle triangle) {     Point3d point1 = triangle.Vertex1.Location;     Point3d point2 = triangle.Vertex2.Location;     Point3d point3 = triangle.Vertex3.Location;       return new Plane(        point1,        point1.GetVectorTo(point2),        point1.GetVectorTo(point3)); } /// <summary> /// 2020年10月31日17:08:49 /// 获取直线与三角形的交点集 /// </summary> /// <param name="l"></param> /// <param name="triangle"></param> /// <returns></returns> public static Point3dCollection GetIntersectPoints(this Line l, TinSurfaceTriangle triangle) {     Point3d point1 = triangle.Vertex1.Location;     Point3d point2 = triangle.Vertex2.Location;     Point3d point3 = triangle.Vertex3.Location;       Point3dCollection result = new Point3dCollection();       l.IntersectWith(new Line(point1, point2), Intersect.OnBothOperands, result, new IntPtr(0), new IntPtr(0));     l.IntersectWith(new Line(point1, point3), Intersect.OnBothOperands, result, new IntPtr(0), new IntPtr(0));     l.IntersectWith(new Line(point3, point2), Intersect.OnBothOperands, result, new IntPtr(0), new IntPtr(0));         return result; }