GetPointOnDynamicDraw Method

using Rhino;
using Rhino.Geometry;
using Rhino.Commands;
using Rhino.Input.Custom;

namespace examples_cs
{
  public class GetPointDynamicDrawCommand : Command
  {
    public override string EnglishName { get { return "csGetPointDynamicDraw"; } }

    protected override Result RunCommand(RhinoDoc doc, RunMode mode)
    {
      var gp = new GetPoint();
      gp.SetCommandPrompt("Center point");
      gp.Get();
      if (gp.CommandResult() != Result.Success)
        return gp.CommandResult();
      var center_point = gp.Point();
      if (center_point == Point3d.Unset)
        return Result.Failure;

      var gcp = new GetCircleRadiusPoint(center_point);
      gcp.SetCommandPrompt("Radius");
      gcp.ConstrainToConstructionPlane(false);
      gcp.SetBasePoint(center_point, true);
      gcp.DrawLineFromPoint(center_point, true);
      gcp.Get();
      if (gcp.CommandResult() != Result.Success)
        return gcp.CommandResult();

      var radius = center_point.DistanceTo(gcp.Point());
      var cplane = doc.Views.ActiveView.ActiveViewport.ConstructionPlane();
      doc.Objects.AddCircle(new Circle(cplane, center_point, radius));
      doc.Views.Redraw();
      return Result.Success;
    }
  }

  public class GetCircleRadiusPoint : GetPoint
  {
    private Point3d m_center_point;

    public GetCircleRadiusPoint(Point3d centerPoint)
    {
      m_center_point = centerPoint;
    }

    protected override void OnDynamicDraw(GetPointDrawEventArgs e)
    {
      base.OnDynamicDraw(e);
      var cplane = e.RhinoDoc.Views.ActiveView.ActiveViewport.ConstructionPlane();
      var radius = m_center_point.DistanceTo(e.CurrentPoint);
      var circle = new Circle(cplane, m_center_point, radius);
      e.Display.DrawCircle(circle, System.Drawing.Color.Black);
    }
  }
}

Imports Rhino
Imports Rhino.Geometry
Imports Rhino.Commands
Imports Rhino.Input.Custom

Namespace examples_vb
  Public Class GetPointDynamicDrawCommand
    Inherits Command
    Public Overrides ReadOnly Property EnglishName() As String
      Get
        Return "vbGetPointDynamicDraw"
      End Get
    End Property

    Protected Overrides Function RunCommand(doc As RhinoDoc, mode As RunMode) As Result
      Dim gp = New GetPoint()
      gp.SetCommandPrompt("Center point")
      gp.[Get]()
      If gp.CommandResult() <> Result.Success Then
        Return gp.CommandResult()
      End If
      Dim center_point = gp.Point()
      If center_point = Point3d.Unset Then
        Return Result.Failure
      End If

      Dim gcp = New GetCircleRadiusPoint(center_point)
      gcp.SetCommandPrompt("Radius")
      gcp.ConstrainToConstructionPlane(False)
      gcp.SetBasePoint(center_point, True)
      gcp.DrawLineFromPoint(center_point, True)
      gcp.[Get]()
      If gcp.CommandResult() <> Result.Success Then
        Return gcp.CommandResult()
      End If

      Dim radius = center_point.DistanceTo(gcp.Point())
      Dim cplane = doc.Views.ActiveView.ActiveViewport.ConstructionPlane()
      doc.Objects.AddCircle(New Circle(cplane, center_point, radius))
      doc.Views.Redraw()
      Return Result.Success
    End Function
  End Class

  Public Class GetCircleRadiusPoint
    Inherits GetPoint
    Private m_center_point As Point3d

    Public Sub New(centerPoint As Point3d)
      m_center_point = centerPoint
    End Sub

    Protected Overrides Sub OnDynamicDraw(e As GetPointDrawEventArgs)
      MyBase.OnDynamicDraw(e)
      Dim cplane = e.RhinoDoc.Views.ActiveView.ActiveViewport.ConstructionPlane()
      Dim radius = m_center_point.DistanceTo(e.CurrentPoint)
      Dim circle = New Circle(cplane, m_center_point, radius)
      e.Display.DrawCircle(circle, System.Drawing.Color.Black)
    End Sub
  End Class
End Namespace

from Rhino import *
from Rhino.Geometry import *
from Rhino.Commands import *
from Rhino.Input.Custom import *
from scriptcontext import doc
from System.Drawing import *

def RunCommand():
  gp = GetPoint()
  gp.SetCommandPrompt("Center point")
  gp.Get()
  if gp.CommandResult() <> Result.Success:
    return gp.CommandResult()
  center_point = gp.Point()
  if center_point == Point3d.Unset:
    return Result.Failure

  gcp = GetCircleRadiusPoint(center_point)
  gcp.SetCommandPrompt("Radius")
  gcp.ConstrainToConstructionPlane(False)
  gcp.SetBasePoint(center_point, True)
  gcp.DrawLineFromPoint(center_point, True)
  gcp.Get()
  if gcp.CommandResult() <> Result.Success:
    return gcp.CommandResult()

  radius = center_point.DistanceTo(gcp.Point())
  cplane = doc.Views.ActiveView.ActiveViewport.ConstructionPlane()
  doc.Objects.AddCircle(Circle(cplane, center_point, radius))
  doc.Views.Redraw()
  return Result.Success

class GetCircleRadiusPoint (GetPoint):
  def __init__(self, centerPoint):
    self.m_center_point = centerPoint

  def OnDynamicDraw(self, e):
    cplane = e.RhinoDoc.Views.ActiveView.ActiveViewport.ConstructionPlane()
    radius = self.m_center_point.DistanceTo(e.CurrentPoint)
    circle = Circle(cplane, self.m_center_point, radius)
    e.Display.DrawCircle(circle, Color.Black)

if __name__ == "__main__":
    RunCommand()