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AutoCAD Tutorial

AutoCAD 3D Modeling: User Coordinate System

July 24, 2003

Every drawing is equipped with a coordinate system called WCS or rather World Coordinate System. The WCS is fixed and you cannot change its location or orientation. Instead the User Coordinate System or rather UCS is used. You can move or rotate UCS in any direction. The placement of objects is based on the current UCS so you can even use 2D commands to create objects in 3D space with various orientations.

There are two toolbars for controlling UCS location and orientation: UCS [Figure 1] and UCS II [Figure 2].

Figure 1

Buttons from left to right:

  • UCS: Invokes the UCS command.

  • Display UCS Dialog: Shows UCS dialog box.

  • UCS Previous: Enables the previous UCS settings.

  • World UCS: Matches the UCS with WCS.

  • Object UCS: Builds the UCS based on the selected object.

  • Face UCS: Builds the UCS based on the selected face.

  • View UCS: Matches UCS with screen. The X axis horizontal, Y vertical, and Z perpendicular to the screen.

  • Origin UCS: Moves the UCS without changing its orientation.

  • Z Axis Vector UCS: Builds the UCS based on the new direction of the Z axis.

  • 3 Point UCS: Builds the UCS by specifying the new origin, a point on positive X direction, and a point on XY plane.

  • X Axis Rotate UCS: Rotates the UCS about X axis.

  • Y Axis Rotate UCS: Rotates the UCS about Y axis.

  • Z Axis Rotate UCS: Rotates the UCS about Z axis.

  • Apply UCS: Applies the current UCS to a selected viewport.

Figure 2

Buttons from left to right:

  • Display UCS Dialog: Shows UCS dialog box.

  • Move UCS Origin: Moves the UCS without changing its orientation.

  • Select UCS drop down list enables you to select an orthographic and/or a saved UCS as the current UCS.

The following tutorial shows you how to use the UCS and UCS II toolbars to manage User Coordinate System.

Note: This tutorial is designed for AutoCAD 2004 though might be applicable for other releases.

1. Download r16_ucs.dwg.

Note: If you are using AutoCAD 2002 or an earlier version, download r15_ucs.dwg.

2. Open the file in AutoCAD. The drawing consists of a box and a circle [Figure 3].

Figure 3

3. Enable UCS toolbar (View menu > Toolbars).

4. Make sure that Endpoint OSnap is enabled.

5. Click View UCS. The UCS is aligned with the screen [Figure 4].

Figure 4

6. Click 3 Point UCS.

7. Click points 4, 3 and 1 as origin, positive x axis and xy plane directions respectively [Figure 5].

Figure 5

8. Click Origin UCS and then click point 7 as the new origin [Figure 6].

Figure 6

9. Click Z Axis Vector UCS.

10. Click point 8 as the origin and point 1 as the direction of Z axis [Figure 7].

Figure 7

11. Click Object UCS and then select the circle [Figure 8]. The orientation of X and Y axes depends on the point that you click.

Figure 8

12. Select Face UCS.

13. Click on the front face near point 8. Press Enter to accept the new settings [Figure 9].

Figure 9

14. Click X Axis Rotate UCS.

15. Rotate the UCS 45 degrees about X axis [Figure 10].

Figure 10

16. Rotate the UCS -45 degrees about Y axis and then 25 degrees about Z axis [Figure 11].

Figure 11

17. Click UCS (i.e. click the first button to the left).

18. Select the Save option and save the current UCS as "sample":

Command: _ucs

Current ucs name: *NO NAME*

Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World]

<World>: s 8

Enter name to save current UCS or [?]: sample 8

19. Click World UCS [Figure 12].

Figure 12

20. Click UCS and restore the "sample" UCS [Figure 13]:

Command: _ucs

Current ucs name: *WORLD*

Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World]

<World>: r 8

Enter name of UCS to restore or [?]: sample 8

Figure 13

21. Click UCS Previous [Figure 14].

Figure 14

22. Invoke the VPORTS command. Divide the drawing area into four equal viewports [Figure 15].

Figure 15 - Click on image to enlarge

Note: For more information on viewports read the following article:
AutoCAD 3D Modeling: Tiled Viewports

23. Enable UCS II toolbar (View menu > Toolbars).

24. Click the upper right corner viewport to make it current.

25. On UCS II click Move UCS Origin.

26. Click point 3. The UCS will be affected on the current viewport only [Figure 16].

Figure 16 - Click on image to enlarge

27. On UCS toolbar click Apply UCS. Apply the current UCS to all viewports [Figure 17].

Command: _ucs

Current ucs name: *NO NAME*

Enter an option [New/Move/orthoGraphic/Prev/Restore/Save/Del/Apply/?/World]

<World>: _apply

Pick viewport to apply current UCS or [All]<current>: all 8

Figure 17 - Click on image to enlarge

28. On View menu select Viewports > 1 Viewport.

29. From the UCS list select, World. Then select Bottom [Figure 18].

Figure 18

30. Click Display UCS Dialog. The UCS dialog box appears [Figure 19].

Figure 19

31. From the list select, sample.

32. Click Set Current.

33. Click OK [Figure 20].

Figure 20


About the Author

Alireza Parsai is the founder of cadpanel.com. He is a mechanical engineer with more than 12 years experience with AutoCAD. Alireza is an Autodesk Authorized Author, the AutoCAD consultant for Al Khawarizmi Institute, a contributing editor for Augiworld magazine, a writer for CAD Digest, an instructor for AUGI Training Program, and an elected speaker for Autodesk University 2002. He has written 7 books in Farsi, 3 booklets in English, and more than 30 articles for different magazines and newsletters. You can reach him at alireza.parsai@cadpanel.com or visit his website www.cadpanel.com

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