Specify 3D Coordinates (.NET)

Entering 3D world coordinate system (WCS) coordinates is similar to entering 2D WCS coordinates. In addition to specifying X and Y values, you specify a Z value. 2D coordinates are represented by a Point2d object, while you use a Point3d object to represent 3D coordinates. Most properties and methods in the AutoCAD .NET API utilize 3D coordinates.

Define and query the coordinates for 2D and 3D polylines

This example creates two polylines, each with three coordinates. The first polyline is a 2D polyline, the second polyline is 3D. Notice that the length of the array containing the vertices is expanded to include the Z coordinates in the creation of the 3D polyline. The example concludes by querying the coordinates of the polylines and displaying the coordinates in a message box.

C# Example

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
 
[CommandMethod("Polyline_2D_3D")]
public static void Polyline_2D_3D()
{
    // Get the current document and database, and start a transaction
    Document acDoc = Application.DocumentManager.MdiActiveDocument;
    Database acCurDb = acDoc.Database;

    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Open the Block table record for read
        BlockTable acBlkTbl;
        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                     OpenMode.ForRead) as BlockTable;

        // Open the Block table record Model space for write
        BlockTableRecord acBlkTblRec;
        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                        OpenMode.ForWrite) as BlockTableRecord;

        // Create a polyline with two segments (3 points)
        using (Polyline acPoly = new Polyline())
        {
            acPoly.AddVertexAt(0, new Point2d(1, 1), 0, 0, 0);
            acPoly.AddVertexAt(1, new Point2d(1, 2), 0, 0, 0);
            acPoly.AddVertexAt(2, new Point2d(2, 2), 0, 0, 0);
            acPoly.ColorIndex = 1;

            // Add the new object to the block table record and the transaction
            acBlkTblRec.AppendEntity(acPoly);
            acTrans.AddNewlyCreatedDBObject(acPoly, true);


            // Create a 3D polyline with two segments (3 points)
            using (Polyline3d acPoly3d = new Polyline3d())
            {
                acPoly3d.ColorIndex = 5;

                // Add the new object to the block table record and the transaction
                acBlkTblRec.AppendEntity(acPoly3d);
                acTrans.AddNewlyCreatedDBObject(acPoly3d, true);

                // Before adding vertexes, the polyline must be in the drawing
                Point3dCollection acPts3dPoly = new Point3dCollection();
                acPts3dPoly.Add(new Point3d(1, 1, 0));
                acPts3dPoly.Add(new Point3d(2, 1, 0));
                acPts3dPoly.Add(new Point3d(2, 2, 0));

                foreach (Point3d acPt3d in acPts3dPoly)
                {
                    using (PolylineVertex3d acPolVer3d = new PolylineVertex3d(acPt3d))
                    {
                        acPoly3d.AppendVertex(acPolVer3d);
                        acTrans.AddNewlyCreatedDBObject(acPolVer3d, true);
                    }
                }

                // Get the coordinates of the lightweight polyline
                Point2dCollection acPts2d = new Point2dCollection();
                for (int nCnt = 0; nCnt < acPoly.NumberOfVertices; nCnt++)
                {
                    acPts2d.Add(acPoly.GetPoint2dAt(nCnt));
                }

                // Get the coordinates of the 3D polyline
                Point3dCollection acPts3d = new Point3dCollection();
                foreach (ObjectId acObjIdVert in acPoly3d)
                {
                    PolylineVertex3d acPolVer3d;
                    acPolVer3d = acTrans.GetObject(acObjIdVert,
                                                   OpenMode.ForRead) as PolylineVertex3d;

                    acPts3d.Add(acPolVer3d.Position);
                }

                // Display the Coordinates
                Application.ShowAlertDialog("2D polyline (red): \n" +
                                            acPts2d[0].ToString() + "\n" +
                                            acPts2d[1].ToString() + "\n" +
                                            acPts2d[2].ToString());

                Application.ShowAlertDialog("3D polyline (blue): \n" +
                                            acPts3d[0].ToString() + "\n" +
                                            acPts3d[1].ToString() + "\n" +
                                            acPts3d[2].ToString());
            }
        }

        // Save the new object to the database
        acTrans.Commit();
    }
}