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AutoCAD Tutorial

AutoCAD 3D Modeling: Creating Regions

August 12, 2003

Regions are special type of objects that look like one-sided flat surfaces. On the other hand regions have similar behavior to 3D solids. You can use regions to create flat surfaces with round edges. The regions can also be used to create 3D solids. There are two commands that are capable of creating regions. The following tutorial shows you how to use them both.

Notes:

  • This tutorial is designed for AutoCAD 2004 though might be applicable to other releases.
  • In this tutorial user entries are in boldface.
  • The 8 symbol represents pressing Enter.

1. Download r16_create_regions.dwg.

Note: If you are using AutoCAD 2002 or an earlier release download r15_create_regions.dwg.

2. Open the drawing in AutoCAD. The drawing consists of some 2D objects [Figure 1].


Figure 1 - Click on image to enlarge

3. Make sure that DELOBJ system variable is equal to 1. If this system variable equals 1 the REGION command will delete the object(s) that are used to create the region(s).

4. Alter the shade mode to Flat shaded.

5. Invoke REGION (Draw menu > Region).

6. Select the ellipse and then press Enter. A region replaces the ellipse [Figure 2].


Figure 2 - Click on image to enlarge

7. Assign 0 to DELOBJ to avoid deletion of original objects:

Command: delobj8
Enter new value for DELOBJ <1>: 08

8. Invoke REGION and then select all objects:

Command: reg8
REGION
Select objects: all8
10 found
Select objects:8
1 closed, degenerate or unsupported object rejected.
1 loop extracted.
1 Region created.

Note: The command has no effect on the existing region to the right. The mid area cannot be converted to a region. It is considered as a complex loop as its boundary objects are not adjoining curves. REGION is incapable to analyze such loops. The only valid loop is the one to the left. The border of the region will remain on the screen due to assigning 1 to DELOBJ [Figure 3].


Figure 3 - Click on image to enlarge

9. To create a region based on a complex loop you can use the BOUNDARY command. Invoke BOUNDARY (Draw menu > Boundary). The Boundary Creation dialog box appears [Figure 4].


Figure 4 - Click on image to enlarge

10. On Object type section select Region from the drop down list.

11. Click Pick Points button to the right. Then click in the middle loop.

12. Press Enter to create the region [Figure 4].


Figure 5
- Click on image to enlarge

Note: BOUNDARY is independent of DELOBJ value. It never removes the boundary objects.

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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