Getting all possible intersection points of multiple lines

[Anonymous]

Can it be possible to get all possible intersection points of multiple lines using Selection Sets or ObjectID collections by selecting lines?

Example this drawing below:

I wanna get the points indicated by the red circle. Can it be done?

[_gile]

Hi,

Yes, it's possible.

Have a look at the Curve.IntersectWith() method.

In your line collection, you'll have to check for intersections between each item and all the following ones. With 4 lines (l1, l2, l3, l4), you may search for intersections betwen l1 and l2, l1 and l3, l1 and l4, then l2 and l3 , l2 and l4, then l3 and l4 (this can asily be implemented with for loops).

[_gile · Accepted solution]

Here's alittle sample

        [CommandMethod("CMD", CommandFlags.UsePickSet)]
        public void Cmd()
        {
            var doc = Application.DocumentManager.MdiActiveDocument;
            var db = doc.Database;
            var ed = doc.Editor;

            var selResult = ed.GetSelection(new SelectionFilter(new[] { new TypedValue(0, "LINE") }));
            if (selResult.Status != PromptStatus.OK) return;

            using (Transaction tr = db.TransactionManager.StartTransaction())
            {
                var selection = selResult.Value;
                var lines = new Line[selection.Count];
                for (int i = 0; i < selection.Count; i++)
                {
                    lines[i] = (Line)tr.GetObject(selection[i].ObjectId, OpenMode.ForRead);
                }

                var space = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
                var points = new Point3dCollection();

                for (int i = 0; i < lines.Length; i++)
                {
                    for (int j = i + 1; j < lines.Length; j++)
                    {
                        points.Clear();
                        lines[i].IntersectWith(lines[j], Intersect.OnBothOperands, points, new IntPtr(0), new IntPtr(0));
                        foreach (Point3d pt in points)
                        {
                            var point = new DBPoint(pt);
                            space.AppendEntity(point);
                            tr.AddNewlyCreatedDBObject(point, true);
                        }
                    }
                }
                tr.Commit();
            }
        }

[Anonymous]

You did an array of lines, nice. Thanks man!