[CommandMethod("CreateArcBy3Points", "cra3p", CommandFlags.Modal | CommandFlags.UsePickSet | CommandFlags.Redraw)]
public void CreateArcByThreePoints()
{
short osm = (short)Autodesk.AutoCAD.ApplicationServices.Application.GetSystemVariable("osmode");
Autodesk.AutoCAD.ApplicationServices.Application.SetSystemVariable("osmode", 0);
Document doc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
Editor ed = doc.Editor;
Database db = doc.Database;
// get the points
Point3d p1, p2, p3;
PromptPointOptions ppo = new PromptPointOptions("\nFirst point: ");
PromptPointResult ppr = ed.GetPoint(ppo);
if (ppr.Status != PromptStatus.OK) return;
p1 = ppr.Value;
ppo = new PromptPointOptions("\nSecond point: ");
ppr = ed.GetPoint(ppo);
if (ppr.Status != PromptStatus.OK) return;
p2 = ppr.Value;
ppo = new PromptPointOptions("\nThird point: ");
ppr = ed.GetPoint(ppo);
if (ppr.Status != PromptStatus.OK) return;
p3 = ppr.Value;
// create a CircularArc3d
CircularArc3d carc = new CircularArc3d(p1, p2, p3);
Arc arc = null;
// now convert the CircularArc3d to an Arc
Point3d cpt = carc.Center;
Vector3d normal = carc.Normal;
Vector3d refVec = carc.ReferenceVector;
Plane plan = new Plane(cpt, normal);
double ang = refVec.AngleOnPlane(plan);
arc = new Arc(cpt, normal, carc.Radius, carc.StartAngle + ang, carc.EndAngle + ang);
arc.SetDatabaseDefaults();
// dispose CircularArc3d
carc.Dispose();
// get the current database
using (Transaction tr = db.TransactionManager.StartTransaction())
{
try
{
// get the current space
BlockTableRecord btr = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
// append arc to space
btr.AppendEntity(arc);
// add arc to transaction
tr.AddNewlyCreatedDBObject(arc, true);
tr.Commit();
}
catch (Autodesk.AutoCAD.Runtime.Exception ex)
{
ed.WriteMessage(ex.Message + "\n" + ex.StackTrace);
}
finally
{
//do nothing (optional)
Autodesk.AutoCAD.ApplicationServices.Application.SetSystemVariable("osmode", osm);
}
}
}
