Define a User Coordinate System

You define a user coordinate system ( UCS ) object to change the location of the (0, 0, 0) origin point and the orientation of the XY plane and Z axis. You can locate and orient a UCS anywhere in 3D space, and you can define, save, and recall as many user coordinate systems as you require. Coordinate input and display are relative to the current UCS.

To indicate the origin and orientation of the UCS, you can display the UCS icon at the UCS origin point using the IconAtOrigin property of a Viewport object or the UCSICON system variable. If the UCS icon is turned on (IconVisible property) and is not displayed at the origin, it is displayed at the WCS coordinate defined by the UCSORG system variable.

You can create a new user coordinate system using the Add method of the UCSTable object. This method requires four values as input: the coordinate of the origin, a coordinate on the X and Y axes, and the name of the UCS.

All coordinates in the AutoCAD^® ActiveX Automation are entered in the world coordinate system. Use the GetUCSMatrix method to return the transformation matrix of a given UCS. Use this transformation matrix to find the equivalent WCS coordinates.

To make a UCS active, use the ActiveUCS property on the Document object. If changes are made to the active UCS, the new UCS object must be reset as the active UCS for the changes to appear. To reset the active UCS, simply call the ActiveUCS property again with the updated UCS object.

For more information about defining a UCS, see “Overview of the User Coordinate System (UCS)” in the AutoCAD User's Guide.

Create a new UCS, make it active, and translate the coordinates of a point into the UCS coordinates

The following subroutine creates a new UCS and sets it as the active UCS for the drawing. It then asks the user to pick a point in the drawing, and returns both WCS and UCS coordinates for the point.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

Imports Autodesk.AutoCAD.EditorInput

Imports Autodesk.AutoCAD.Geometry

<CommandMethod("NewUCS")> _

Public Sub NewUCS()

  '' Get the current document and database, and start a transaction

  Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument

  Dim acCurDb As Database = acDoc.Database

  Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

      '' Open the UCS table for read

      Dim acUCSTbl As UcsTable

      acUCSTbl = acTrans.GetObject(acCurDb.UcsTableId, _

                                   OpenMode.ForRead)

      Dim acUCSTblRec As UcsTableRecord

      '' Check to see if the "New_UCS" UCS table record exists

      If acUCSTbl.Has("New_UCS") = False Then

          acUCSTblRec = New UcsTableRecord()

          acUCSTblRec.Name = "New_UCS"

          '' Open the UCSTable for write

          acUCSTbl.UpgradeOpen()

          '' Add the new UCS table record

          acUCSTbl.Add(acUCSTblRec)

          acTrans.AddNewlyCreatedDBObject(acUCSTblRec, True)

      Else

          acUCSTblRec = acTrans.GetObject(acUCSTbl("New_UCS"), _

                                          OpenMode.ForWrite)

      End If

      acUCSTblRec.Origin = New Point3d(4, 5, 3)

      acUCSTblRec.XAxis = New Vector3d(1, 0, 0)

      acUCSTblRec.YAxis = New Vector3d(0, 1, 0)

      '' Open the active viewport

      Dim acVportTblRec As ViewportTableRecord

      acVportTblRec = acTrans.GetObject(acDoc.Editor.ActiveViewportId, _

                                        OpenMode.ForWrite)

      '' Display the UCS Icon at the origin of the current viewport

      acVportTblRec.IconAtOrigin = True

      acVportTblRec.IconEnabled = True

      '' Set the UCS current

      acVportTblRec.SetUcs(acUCSTblRec.ObjectId)

      acDoc.Editor.UpdateTiledViewportsFromDatabase()

      '' Display the name of the current UCS

      Dim acUCSTblRecActive As UcsTableRecord

      acUCSTblRecActive = acTrans.GetObject(acVportTblRec.UcsName, _

                                            OpenMode.ForRead)

      Application.ShowAlertDialog("The current UCS is: " & _

                                  acUCSTblRecActive.Name)

      Dim pPtRes As PromptPointResult

      Dim pPtOpts As PromptPointOptions = New PromptPointOptions("")

      '' Prompt for a point

      pPtOpts.Message = vbLf & "Enter a point: "

      pPtRes = acDoc.Editor.GetPoint(pPtOpts)

      Dim pPt3dWCS As Point3d

      Dim pPt3dUCS As Point3d

      '' If a point was entered, then translate it to the current UCS

      If pPtRes.Status = PromptStatus.OK Then

          pPt3dWCS = pPtRes.Value

          pPt3dUCS = pPtRes.Value

          '' Translate the point from the current UCS to the WCS

          Dim newMatrix As Matrix3d = New Matrix3d()

          newMatrix = Matrix3d.AlignCoordinateSystem(Point3d.Origin, _

                                                     Vector3d.XAxis, _

                                                     Vector3d.YAxis, _

                                                     Vector3d.ZAxis, _

                                                     acVportTblRec.Ucs.Origin, _

                                                     acVportTblRec.Ucs.Xaxis, _

                                                     acVportTblRec.Ucs.Yaxis, _

                                                     acVportTblRec.Ucs.Zaxis)

          pPt3dWCS = pPt3dWCS.TransformBy(newMatrix)

          Application.ShowAlertDialog("The WCS coordinates are: " & vbLf & _

                                      pPt3dWCS.ToString() & vbLf & _

                                      "The UCS coordinates are: " & vbLf & _

                                      pPt3dUCS.ToString())

      End If

      '' Save the new objects to the database

      acTrans.Commit()

  End Using

End Sub

using Autodesk.AutoCAD.Runtime;

using Autodesk.AutoCAD.ApplicationServices;

using Autodesk.AutoCAD.DatabaseServices;

using Autodesk.AutoCAD.EditorInput;

using Autodesk.AutoCAD.Geometry;

[CommandMethod("NewUCS")]

public static void NewUCS()

  // 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 UCS table for read

      UcsTable acUCSTbl;

      acUCSTbl = acTrans.GetObject(acCurDb.UcsTableId,

                                   OpenMode.ForRead) as UcsTable;

      UcsTableRecord acUCSTblRec;

      // Check to see if the "New_UCS" UCS table record exists

      if (acUCSTbl.Has("New_UCS") == false)

          acUCSTblRec = new UcsTableRecord();

          acUCSTblRec.Name = "New_UCS";

          // Open the UCSTable for write

          acUCSTbl.UpgradeOpen();

          // Add the new UCS table record

          acUCSTbl.Add(acUCSTblRec);

          acTrans.AddNewlyCreatedDBObject(acUCSTblRec, true);

      else

          acUCSTblRec = acTrans.GetObject(acUCSTbl["New_UCS"],

                                          OpenMode.ForWrite) as UcsTableRecord;

      acUCSTblRec.Origin = new Point3d(4, 5, 3);

      acUCSTblRec.XAxis = new Vector3d(1, 0, 0);

      acUCSTblRec.YAxis = new Vector3d(0, 1, 0);

      // Open the active viewport

      ViewportTableRecord acVportTblRec;

      acVportTblRec = acTrans.GetObject(acDoc.Editor.ActiveViewportId,

                                        OpenMode.ForWrite) as ViewportTableRecord;

      // Display the UCS Icon at the origin of the current viewport

      acVportTblRec.IconAtOrigin = true;

      acVportTblRec.IconEnabled = true;

      // Set the UCS current

      acVportTblRec.SetUcs(acUCSTblRec.ObjectId);

      acDoc.Editor.UpdateTiledViewportsFromDatabase();

      // Display the name of the current UCS

      UcsTableRecord acUCSTblRecActive;

      acUCSTblRecActive = acTrans.GetObject(acVportTblRec.UcsName,

                                            OpenMode.ForRead) as UcsTableRecord;

      Application.ShowAlertDialog("The current UCS is: " +

                                  acUCSTblRecActive.Name);

      PromptPointResult pPtRes;

      PromptPointOptions pPtOpts = new PromptPointOptions("");

      // Prompt for a point

      pPtOpts.Message = "\nEnter a point: ";

      pPtRes = acDoc.Editor.GetPoint(pPtOpts);

      Point3d pPt3dWCS;

      Point3d pPt3dUCS;

      // If a point was entered, then translate it to the current UCS

      if (pPtRes.Status == PromptStatus.OK)

          pPt3dWCS = pPtRes.Value;

          pPt3dUCS = pPtRes.Value;

          // Translate the point from the current UCS to the WCS

          Matrix3d newMatrix = new Matrix3d();

          newMatrix = Matrix3d.AlignCoordinateSystem(Point3d.Origin,

                                                     Vector3d.XAxis,

                                                     Vector3d.YAxis,

                                                     Vector3d.ZAxis,

                                                     acVportTblRec.Ucs.Origin,

                                                     acVportTblRec.Ucs.Xaxis,

                                                     acVportTblRec.Ucs.Yaxis,

                                                     acVportTblRec.Ucs.Zaxis);

          pPt3dWCS = pPt3dWCS.TransformBy(newMatrix);

          Application.ShowAlertDialog("The WCS coordinates are: \n" +

                                      pPt3dWCS.ToString() + "\n" +

                                      "The UCS coordinates are: \n" +

                                      pPt3dUCS.ToString());

      // Save the new objects to the database

      acTrans.Commit();

VBA/ActiveX Code Reference