Newly created Line cannot use intersectWith to another created Line

[alexisgacia]

Hi Guys,

Im new in VB.Net. I tried to create basic objects using Lines circle and try to get the intersection of 2 objects. But it give me some errors.

What I did is to select polyline then another line that is cross to the polyline. After the selecting 2 objects it will detect the intersection and the program will give Points3D. using the points given I will create temporary objects like circle and check the intersection. Thats the error area, were I cannot get the intersection points of the temporary circle and the selected line.

Another problem that I tried is new objects to be intersect to another new objects it will gives error as well.

I hope somebody understand my problem.

Thanks in advance.

Regards,

Alex

[Keith.Brown]

I might be wrong but I believe that any entities that you use with IntersectsWith will need to be added to the database and have an ObjectId.  

[_gile · Accepted solution]

Hi,

Here's a working example with an existing polyline and a temporary circle (i.e. the newly created circle is not added to the database).

This example is written in C#, you could convert it with telerik code converter for example*, but assuming you're starting with .NET you should learn C# instead of VB because you'll find more valuable help and examples in C#.

        [CommandMethod("TEST")]
        public static void Test()
        {
            var doc = AcAp.DocumentManager.MdiActiveDocument;
            var db = doc.Database;
            var ed = doc.Editor;

            // prompt the use to select a polyline
            var peo = new PromptEntityOptions("\nSelect Polyline: ");
            peo.SetRejectMessage("\nMust be a Polyline.");
            peo.AddAllowedClass(typeof(Polyline), true);
            var per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK) 
                return;

            // prompt the user to specify center of the circle
            var ppr = ed.GetPoint("\nSpecify the center: ");
            if (ppr.Status != PromptStatus.OK)
                return;

            // prompt the user to specify the radius of the circle
            var pdo = new PromptDistanceOptions("\nSpecify the radius: ");
            pdo.BasePoint = ppr.Value;
            pdo.UseBasePoint = true;
            var pdr = ed.GetDistance(pdo);
            if (pdr.Status != PromptStatus.OK)
                return;

            using (var tr = db.TransactionManager.StartTransaction())
            {
                // open the selected polyline for read
                var pline = (Polyline)tr.GetObject(per.ObjectId, OpenMode.ForRead);
                var points = new Point3dCollection();

                // create a temporary circle
                var center = ppr.Value.TransformBy(ed.CurrentUserCoordinateSystem);
                double radius = pdr.Value;
                // the using statement insures the circle to be disposed instead of been added to the database
                using (var circle = new Circle(center, Vector3d.ZAxis, radius))
                {
                    // search for intersection
                    pline.IntersectWith(circle, Intersect.OnBothOperands, points, IntPtr.Zero, IntPtr.Zero);

                    // print the output
                    if (points.Count > 0)
                    {
                        ed.WriteMessage("\nIntersections:");
                        foreach (Point3d point in points)
                        {
                            ed.WriteMessage($" {point:0.00}");
                        }
                    }
                    else
                    {
                        ed.WriteMessage("\nNone intersection.");
                    }
                }
                tr.Commit();
            }
        }

*if you use some automatic converter to convert C# to VB, take care the VB "Infer" and "Strict" options are "On" in your project

[alexisgacia]

Many thanks.

Whole day I tried to find the answer and you just did it in just a couple of minutes. 

Once again many thanks.

[_gile · Accepted solution]

Instead of creating "temporary entities" for solving geometrical issues, you can use the the geometrical object from the Autodesk.AutoCAD.Geometry namespace.

Here's an example converting a selected Line entity into a LineSegment3d and creating a CircularArc3d to serach intersections.

        [CommandMethod("TEST")]
        public static void Test()
        {
            var doc = AcAp.DocumentManager.MdiActiveDocument;
            var db = doc.Database;
            var ed = doc.Editor;

            // prompt the use to select a line
            var peo = new PromptEntityOptions("\nSelect Line: ");
            peo.SetRejectMessage("\nMust be a Polyline.");
            peo.AddAllowedClass(typeof(Line), true);
            var per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK)
                return;

            // prompt the user to specify center of the circle
            var ppr = ed.GetPoint("\nSpecify the center: ");
            if (ppr.Status != PromptStatus.OK)
                return;

            // prompt the user to specify the radius of the circle
            var pdo = new PromptDistanceOptions("\nSpecify the radius: ");
            pdo.BasePoint = ppr.Value;
            pdo.UseBasePoint = true;
            var pdr = ed.GetDistance(pdo);
            if (pdr.Status != PromptStatus.OK)
                return;

            // get a geometrical line form the selected line
            LineSegment3d line;
            using (var tr = new OpenCloseTransaction())
            {
                var pline = (Line)tr.GetObject(per.ObjectId, OpenMode.ForRead);
                line = (LineSegment3d)pline.GetGeCurve();
            }

            // create a geometrical circle
            var center = ppr.Value.TransformBy(ed.CurrentUserCoordinateSystem);
            double radius = pdr.Value;
            var circle = new CircularArc3d(center, Vector3d.ZAxis, radius);

            // search for intersections betwen the line and circle
            var points = circle.IntersectWith(line);
            if (points != null)
            {
                ed.WriteMessage("\nIntersections:");
                foreach (Point3d point in points)
                {
                    ed.WriteMessage($" {point:0.00}");
                }
            }
            else
            {
                ed.WriteMessage("\nNone intersection.");
            }
        }

[alexisgacia]

Hi Gile,

Thank you for the tip. Very helpful. 

I think this is the best approach rather than making temporary objects. 

Many thanks again.

Best regards,

Alex