The closest point to the curve

Rhino Developer
1

I need to find out the closest point on the curve… The point that the ClosestPoint () method used in the curve class is not the closest point… I don’t know what’s going on.

2

Can you post an example of this? I think it’s hard to tell what is going on without the geometry and code.

-Willem

3

get closest point on curve:

const ON_Curve* tempCurve =…;
ON_3dPoint pt_closest;
double t=0.0;
if (tempCurve->GetClosestPoint(pt,&t))
{
pt_closest=tempCurve->PointAt(t);
}

4 

       Curve s_cur = s_obj.Curve(); //Here is the object converted to the curve

       Curve g_cur = g_obj.Curve();//Here is the object converted to the curve

       //The reconstructed curves are obtained from NurbsCurve

       NurbsCurve n_cur1 = g_cur.ToNurbsCurve().Rebuild(s_cur.ToNurbsCurve().Points.Count,3,true);
       NurbsCurve n_cur2 = g_cur.ToNurbsCurve().Rebuild(g_cur.ToNurbsCurve().Points.Count,3,true);

        //The closest point on the curve obtained from the control point to curve 1 is on the curve 2.

       List<Point3d> c_pt= new List<Point3d>();
       for (int i = 0; i < g_n_cur.Points.Count; i++)
       {
           doc.Objects.AddPoint(g_n_cur.Points[i].Location);
           double t;
          n_cur2.ClosestPoint(n_cur1.Points[i].Location, out t);
           Point3d pt = n_cur2.PointAt(t);
          c_pt.Add(pt);
       }

The above is a section of code, can get to the point to add to the Rhino is always wrong, all the points are on the Curve1

5 

  NurbsCurve cur2 = g_cur.ToNurbsCurve().Rebuild(s_cur.ToNurbsCurve().Points.Count,3,true);
       NurbsCurve cur1 = g_cur.ToNurbsCurve().Rebuild(g_cur.ToNurbsCurve().Points.Count,3,true);

     List<Point3d> c_pt = new List<Point3d>();
       for (int i = 0; i < cur1.Points.Count; i++)
       {
           double t;
           cur2.ClosestPoint(cur1.Points[i].Location, out t);
           c_pt..Add(pt);
       }
6

NurbsCurve cur1 = g_cur.ToNurbsCurve().Rebuild(s_cur.ToNurbsCurve().Points.Count,3,true);
NurbsCurve cur2 = g_cur.ToNurbsCurve().Rebuild(g_cur.ToNurbsCurve().Points.Count,3,true);
List c_pt = new List();
for (int i = 0; i < cur2.Points.Count; i++)
{
double t;
cur1.ClosestPoint(cur2.Points[i].Location, out t);
Point3d pt = s_n_cur.PointAt(t);
c_pt.Add(pt);
}

7 
       NurbsCurve cur1 = g_cur.ToNurbsCurve().Rebuild(s_cur.ToNurbsCurve().Points.Count,3,true);
       NurbsCurve cur2 = g_cur.ToNurbsCurve().Rebuild(g_cur.ToNurbsCurve().Points.Count,3,true);

       List<Point3d> c_pt = new List<Point3d>();

       for (int i = 0; i < cur1.Points.Count; i++)
       {
           double t;
           cur2.ClosestPoint(cur1.Points[i].Location, out t);
           Point3d pt = s_n_cur.PointAt(t);
        c_pt.Add(pt)
       }
8 
       NurbsCurve cur1 = g_cur.ToNurbsCurve().Rebuild(s_cur.ToNurbsCurve().Points.Count,3,true);
       NurbsCurve cur2 = g_cur.ToNurbsCurve().Rebuild(g_cur.ToNurbsCurve().Points.Count,3,true);

       List<Point3d> c_pt = new List<Point3d>();

       for (int i = 0; i < cur1.Points.Count; i++)
       {
           double t;
           cur2.ClosestPoint(cur1.Points[i].Location, out t);
           Point3d pt = cur2.PointAt(t);
        c_pt.Add(pt)
       }
9

Ok, and now a curve and a point in a 3dm file that reproduce the problem. The code looks good to me.