Region Bounding Box In 3D Coordinate

[thannaingoo.api]

Dear All,

How to get region bounding box in 3D coordinate?

I used below code to extract the bounding box of a region.

The result is not same as massprop value.

How should I get the correct value of region bounding box base on the current coordinate system? 

Thanks,

Naing Oo

var region = (Region)tr.GetObject(id, OpenMode.ForWrite, false, true);

                                if (region.Area > 0.0)
                                {                   
                                    Point3d max = region.Bounds.Value.MaxPoint;
                                    Point3d min = region.Bounds.Value.MinPoint;                                
                                    Application.ShowAlertDialog(min.ToString() + "\n" + max.ToString());
                                }

[BKSpurgeon]

The below link shows how to transform from one coordinate system to another.

https://knowledge.autodesk.com/search-result/caas/CloudHelp/cloudhelp/2015/ENU/AutoCAD-NET/files/GUI...

(In your case you will have to go from the WCS to UCS.)

[thannaingoo.api]

I still can't get the right value. Below image green color is region and the red color is a bounding box from the result.

How should I fix it? Below is the latest code.

Thanks,

Naing Oo

 var region = (Region)tr.GetObject(id, OpenMode.ForWrite, false, true);

                                if (region.Area > 0.0)
                                {
                                    Point3d MaxPoint = region.Bounds.Value.MaxPoint;
                                    Point3d MinPoint = region.Bounds.Value.MinPoint;
                                    Point3d max = MaxPoint.TransformBy(Matrix3d.PlaneToWorld(region.Normal));
                                    Point3d min = MinPoint.TransformBy(Matrix3d.PlaneToWorld(region.Normal));
                                    Application.ShowAlertDialog(max.ToString() + "\n" + min.ToString());
                                }

[_gile]

Hi,

You have to transform the region object from current UCS to WCS, get the extents, and transform back the region to UCS.

var region = (Region)tr.GetObject(id, OpenMode.ForWrite);
                region.TransformBy(ed.CurrentUserCoordinateSystem.Inverse());
                var extents = region.GeometricExtents;
                region.TransformBy(ed.CurrentUserCoordinateSystem);
                ed.WriteMessage($"\nBoundingBox about UCS: {extents.MinPoint} {extents.MaxPoint}");

[thannaingoo.bim.mep]

Dear @_gile,

Thank you for the reply.

I got the wrong value for 45degree rotated region object along Zaxis.

Please, Let me know the way how to solve it.

Regards,

Naing Oo

[thannaingoo.api]

I am trying to create a rectangle of region object bounding box in 3D coordinate.

Let me know the way to create a bounding box rectangle. 

Regards,

Naing Oo

[_gile · Accepted solution]

If I do not misuderstand, what you want to achieve is not related to the current UCS. it is related to the region OCS.

Try like this:

        [CommandMethod("RegionToBoundingBoxRectangle")]
        public static void RegionToBoundingBoxRectangle()
        {
            var doc = Application.DocumentManager.MdiActiveDocument;
            var db = doc.Database;
            var ed = doc.Editor;
            var peo = new PromptEntityOptions("\nSelect region: ");
            peo.SetRejectMessage("\nSelected object is not a Region.");
            peo.AddAllowedClass(typeof(Region), true);
            var per = ed.GetEntity(peo);
            if (per.Status != PromptStatus.OK)
                return;
            var id = per.ObjectId;
            using (var tr = db.TransactionManager.StartTransaction())
            {
                var region = (Region)tr.GetObject(id, OpenMode.ForWrite);
                // get the region plane normal
                var normal = region.Normal;
                var plane = new Plane(Point3d.Origin, normal);
                // transform the region from WCS to OCS
                region.TransformBy(Matrix3d.WorldToPlane(plane));
                // get the 'bounding box'
                var extents = region.GeometricExtents;
                // transform bak the region from OCS to WCS
                region.TransformBy(Matrix3d.PlaneToWorld(plane));
                // get the plane elevation
                var elevation = extents.MaxPoint.Z;
                // get the bounding box coorinates (OCS)
                var minX = extents.MinPoint.X;
                var minY = extents.MinPoint.Y;
                var maxX = extents.MaxPoint.X;
                var maxY = extents.MaxPoint.Y;
                // create a rectangle (Polyline)
                var pline = new Polyline(4);
                pline.AddVertexAt(0, new Point2d(minX, minY), 0.0, 0.0, 0.0);
                pline.AddVertexAt(1, new Point2d(maxX, minY), 0.0, 0.0, 0.0);
                pline.AddVertexAt(2, new Point2d(maxX, maxY), 0.0, 0.0, 0.0);
                pline.AddVertexAt(3, new Point2d(minX, maxY), 0.0, 0.0, 0.0);
                pline.Closed = true;
                pline.Normal = normal;
                pline.Elevation = elevation;
                var curSpace = (BlockTableRecord)tr.GetObject(db.CurrentSpaceId, OpenMode.ForWrite);
                curSpace.AppendEntity(pline);
                tr.AddNewlyCreatedDBObject(pline, true);
                tr.Commit();
            }

[thannaingoo.api]

Dear @_gile,

I want to thank you for taking the time out to answer my question. I am sure that you are busy, and I appreciate you taking the time to respond. Thank you again.

Regards,

Naing Oo