Orientation Curve No Closed

Rhino Developer
1

Hello.

I´m programming a project with C# and rhinho

I want to know the orientation of a curve when this curve is not closed.

Thank you.

2

When you have a Curve object, you can ask for PointAtStart and PointAtEnd.
This can give an idea of the orientation of the curve.

Also, you can ask for TangentAt(t) where t is in the curve domain. This is a tangent vector that is oriented “in the direction of the curve”.

Curve crv;
Point3d startPoint = crv.PointAtStart;
Point3d endPoint = crv.PointAtEnd;

double t = crv.Domain.Mid;
Vector3d midCurveTangent = crv.TangentAt(t);
3

Can I know if the orientation is Clockwise or CounterClockwise?

When the curve is closed I use this:

CurveOrientation orientation = curva.ClosedCurveOrientation(plano);
if (orientation == CurveOrientation.Clockwise)
    ....
else
   ...
4

No. You could temporarily close the curve if that makes any sense in your case.

Curve open; // defined elsewhere
PolyCurve closed = new PolyCurve();
closed.Append(open);
closed.Append(new LineCurve(closed.PointAtEnd, closed.PointAtStart));
CurveOrientation o = closed.ClosedCurveOrientation(plano);
5

Hi,

I’ve the same problem, but I want to get the orientation of line.

I’ve modify the menno algotirhm adding a intermide line, else I can’t get the orientation

        Curve open = (Curve)curva.Duplicate(); // defined elsewhere

PolyCurve closed = new PolyCurve();
            closed.Append(open);
            Point3d ptoIntermedio = closed.PointAtEnd;
            ptoIntermedio.Z += 5;
            closed.Append(new LineCurve(closed.PointAtEnd, ptoIntermedio));
            closed.Append(new LineCurve(ptoIntermedio, closed.PointAtStart));
            closed.TryGetPlane(out plano);
            CurveOrientation orientacionCurva = closed.ClosedCurveOrientation(plano);

if ( orientacionCurva != orientacion)
                curva.Reverse();

But the code is ugly… there is a better algotirhm to set the orientation?

6

A line does not have a clockwise/counter-clockwise orientation. But a line does have a direction.

Rhino.Geometry.Vector3d dir = line.To - line.From;

You can compare this vector to whatever to determine its orientation…

7

Ok.

I need the orientation because I want import from a dxf that contains lines and structure of model, and I’ve to build a model from this lines.

As the dxf only are curves, I always need set the same direction to obtain always the same point start and point end to build the model. If the direction is inverted the model isn’t built well

8

To see if two curves are “more or less traveling in the same direction”, use Curve.DoDirectionsMatch
Maybe it is useful?

See http://4.rhino3d.com/5/rhinocommon/html/M_Rhino_Geometry_Curve_DoDirectionsMatch.htm