Curve.CurvatureAt

Public Class

Evaluate the curvature vector at a curve parameter.

Namespace: Rhino.Geometry

Assembly: RhinoCommon (in RhinoCommon.dll)

**Since:**5.0

Syntax

public Vector3d CurvatureAt(
  double t
)

Parameters

t

Type:System.Double
Evaluation parameter.

Return Value

Type: Vector3d
Curvature vector of the curve at the parameter t.

Remarks

No error handling.

Examples

using Rhino;
using Rhino.DocObjects;
using Rhino.Commands;
using Rhino.Geometry;
using Rhino.Input;

namespace examples_cs
{
  public class AddRadialDimensionCommand : Rhino.Commands.Command
  {
    public override string EnglishName
    {
      get { return "csAddRadialDimension"; }
    }

    protected override Result RunCommand(RhinoDoc doc, RunMode mode)
    {
      ObjRef obj_ref;
      var rc = RhinoGet.GetOneObject("Select curve for radius dimension",
        true, ObjectType.Curve, out obj_ref);
      if (rc != Result.Success)
        return rc;
      double curve_parameter;
      var curve = obj_ref.CurveParameter(out curve_parameter);
      if (curve == null)
        return Result.Failure;

      if (curve.IsLinear() || curve.IsPolyline())
      {
        RhinoApp.WriteLine("Curve must be non-linear.");
        return Result.Nothing;
      }

      // in this example just deal with planar curves
      if (!curve.IsPlanar())
      {
        RhinoApp.WriteLine("Curve must be planar.");
        return Result.Nothing;
      }

      var point_on_curve = curve.PointAt(curve_parameter);
      var curvature_vector = curve.CurvatureAt(curve_parameter);
      var len = curvature_vector.Length;
      if (len < RhinoMath.SqrtEpsilon)
      {
        RhinoApp.WriteLine("Curve is almost linear and therefore has no curvature.");
        return Result.Nothing;
      }

      var center = point_on_curve + (curvature_vector/(len*len));
      Plane plane;
      curve.TryGetPlane(out plane);
      var radial_dimension =
        new RadialDimension(center, point_on_curve, plane.XAxis, plane.Normal, 5.0);
      doc.Objects.AddRadialDimension(radial_dimension);
      doc.Views.Redraw();
      return Result.Success;
    }
  }
}

from Rhino import *
from Rhino.DocObjects import *
from Rhino.Commands import *
from Rhino.Geometry import *
from Rhino.Input import *
from scriptcontext import doc

def RunCommand():
  rc, obj_ref = RhinoGet.GetOneObject("Select curve for radius dimension",
    True, ObjectType.Curve)
  if rc != Result.Success:
    return rc
  curve, curve_parameter = obj_ref.CurveParameter()
  if curve == None:
    return Result.Failure

  if curve.IsLinear() or curve.IsPolyline():
    print "Curve must be non-linear."
    return Result.Nothing

  # in this example just deal with planar curves
  if not curve.IsPlanar():
    print "Curve must be planar."
    return Result.Nothing

  point_on_curve = curve.PointAt(curve_parameter)
  curvature_vector = curve.CurvatureAt(curve_parameter)
  len = curvature_vector.Length
  if len < RhinoMath.SqrtEpsilon:
    print "Curve is almost linear and therefore has no curvature."
    return Result.Nothing

  center = point_on_curve + (curvature_vector/(len*len))
  _, plane = curve.TryGetPlane()
  radial_dimension = \
    RadialDimension(center, point_on_curve, plane.XAxis, plane.Normal, 5.0)
  doc.Objects.AddRadialDimension(radial_dimension)
  doc.Views.Redraw()
  return Result.Success

if __name__=="__main__":
  RunCommand()