How can I know the surface's edge is going in the U direction or the V direction

Rhino Developer
1

Hi,
I have selected a surface edge, is this a way to know surface’s edge is going in the U direction or the V direction ?

   CRhinoGetObject go;
   go.SetCommandPrompt(L"select surface edge");
   go.SetGeometryFilter(CRhinoGetObject::curve_object);
   go.GetObjects(1, 1);
   if (go.CommandResult() != CRhinoCommand::success)
    {
          return;
    }
    const CRhinoObjRef& objRef = go.Object(0);
    const ON_BrepEdge* edge = objRef.Edge();
    ON_Brep* br = objRef.Edge()->Brep();

dir

2

private void RunScript(Surface surface, List edgeList, ref object A)
{
var nurbSrf = surface.ToNurbsSurface();

List<String> values = new List<String>();
for (int i = 0; i < edgeList.Count; i++)
{
  var length = edgeList[i].GetLength();
  if ( length > nurbSrf.IsoCurve(0, 0).GetLength() - 0.001 && length < nurbSrf.IsoCurve(0, 0).GetLength() + 0.001 )
  {
    values.Add("U");
  }
  else
  {
    values.Add("V");
  }
}

A = values;

}

Surfacee Edge direction.gh (8.2 KB)

3

Hi@ mahanmotamedi1991,
Thank you for your replay, you gave me a good idea :grinning:.
But it will have error when the U direction and the V direction of the surface have the same edge length.

2233
22331625×693 105 KB

4

Hi @suc_kiet,

What about this condition, where the edge does not follow the natural boundary of the surface?

image
Or are you dealing with untrimmed surfaces?

– Dale

5

Hi@ dale,
I’m sorry I forgot to explain this.
Yes, I just dealing with untrimmed surfaces. :grinning:

6

Hi @suc_kiet,

How about this?

CRhinoCommand::result CCommandTest::RunCommand(const CRhinoCommandContext& context)
{
  CRhinoGetObject go;
  go.SetCommandPrompt(L"Select edge");
  go.SetGeometryFilter(CRhinoObject::curve_object);
  go.SetGeometryAttributeFilter(CRhinoGetObject::edge_curve);
  go.GetObjects(1, 1);
  if (go.CommandResult() != CRhinoCommand::success)
    return go.CommandResult();

  const CRhinoObjRef& objRef = go.Object(0);

  const ON_BrepEdge* edge = objRef.Edge();
  if (nullptr == edge)
    return CRhinoCommand::failure;

  if (edge->IsClosed())
    return CRhinoCommand::cancel;

  const ON_Brep* brep = edge->Brep();
  if (nullptr == brep)
    return CRhinoCommand::failure;

  if (!brep->IsSurface())
    return CRhinoCommand::cancel;

  const ON_Surface* srf = brep->m_S[0];
  if (nullptr == srf)
    return CRhinoCommand::failure;

  double u0, u1, v0, v1;
  if (
    srf->GetClosestPoint(edge->PointAtStart(), &u0, &v0) &&
    srf->GetClosestPoint(edge->PointAtEnd(), &u1, &v1)
    )
  {
    if (fabs(u0 - u1) < ON_ZERO_TOLERANCE)
      RhinoApp().Print(L"Edge oriented in surface \"V\" direction\n");
    else
      RhinoApp().Print(L"Edge oriented in surface \"U\" direction\n");
  }

  return CRhinoCommand::success;
}

– Dale

7

private void RunScript(Surface surface, List edgeList, ref object A)
{
var nurbSrf = surface.ToNurbsSurface();

List<String> values = new List<String>();

for(int i = 0; i < edgeList.Count; i++)
{
  var crv = edgeList[i];
  var iCrv = nurbSrf.IsoCurve(0, 0);
  var stPt = crv.PointAt(0);
  var endPt = crv.PointAt(1);
  var stPtI = iCrv.PointAt(0);
  var endPtI = iCrv.PointAt(1);
  Vector3d vec1 = endPt - stPt;
  Vector3d vec2 = endPtI - stPtI;

  if( vec1.IsParallelTo(vec2) == 1 || vec1.IsParallelTo(vec2) == -1)

  {
    values.Add("U");
  }
  else
  {
    values.Add("V");
  }
}


A = values;

This will work if your surface is not freeform :wink:
Surfacee Edge direction_Edited.gh (6.0 KB)

8

Hi@dale,
Thank you.

9

Hi@ mahanmotamedi1991,
Thank you.