Using the Fence to Manipulate and Modify Elements

In addition to using the Element Selection or PowerSelector tools to group elements for manipulation, you can group elements with the fence. The fence creates a temporary grouping of elements that is ended when the DGN file is closed, if not before. For information about permanent groupings, see Permanently Grouping Elements.

Most often, the fence is placed around elements to group them for manipulation, just as the pointer is dragged around elements to select them with the Element Selection tool. However, the fence has two additional grouping capabilities. It can be used:

• As a void to exclude elements inside (or overlapping) the fence boundary.

• To clip elements that cross the fence boundary, like a cookie cutter, so that only the parts inside the fence boundary (or outside in the case of a void) are subject to manipulation.

The fence can be rectangular (referred to as a fence block), polygonal (non-rectangular, referred to as a fence shape, with as many as 5000 vertices), or circular (referred to as a fence circle). A fence shape can be derived from a previously placed shape element.

The Place Fence tool is used to place the fence. On placement, the fence — whether it is a fence block, shape, or circle — is displayed on screen as a closed shape with the color used to highlight identified elements. While the fence is placed, a fence mode icon is displayed in the status bar.

Fences are persistent in both 3D and 2D DGN files. You can place a fence, zoom in on the design and the fence will remain when you zoom back out.

To remove the fence if it is already displayed

1. In the Fence tool box, select the Place Fence tool and continue with your work. (In the Main tool frame, Place Fence is the default “representative” from the Fence tool box.)

You can remove the fence this way to prevent accidental fence manipulations.

Specifying which elements are in the fence contents

The Fence (Selection) Mode determines just what constitutes the fence contents — that is, whether the elements (or parts of elements) inside, outside, or overlapping the fence are “contained” by the fence to be processed.

• Inside — Only those elements completely inside the fence are processed.

• Overlap — Only those elements inside or overlapping the fence are processed.

• Clip — Only elements completely inside the fence and parts of elements inside and overlapping the fence are processed.
  see footnote 17

• Void — Only those elements completely outside the fence are processed.

• Void-Overlap — Only those elements outside or overlapping the fence are processed.

• Void-Clip — Only elements completely outside the fence and parts of elements outside and overlapping the fence are processed.
  see footnote 18

  Fence selection modes. Top, the fence and elements. Center Left: Inside; Center Middle: Overlap; Center Right: Clip. Bottom Left: Void; Bottom Middle: Void-Overlap; Bottom Right: Void-Clip.

The Fence Selection Mode is a tool setting (labeled Fence Mode) for the fence tools in the Fence tool box as well as for manipulation tools that can operate on the fence contents. In the latter case, it is set with the option menu next to the Use Fence control. There is also a control in the Locks dialog box.

Examples of Tool Settings window controls for setting the Fence Selection Mode.

It is not necessary to place the fence in order to set the Fence Selection Mode. Conversely, once the fence is placed, you can adjust the Fence Selection Mode to change the fence contents without moving or replacing the fence.

To manipulate the fence contents

1. Place the fence.


2. Select an element manipulation tool that can be used with the fence contents.


3. In the Tool Settings window, turn on Use Fence and set the Fence Selection Mode.
   You are prompted, usually for a data point. For example, with the Delete Fence Contents tool, you are prompted to “Accept/Reject Fence Contents.”


4. Enter a data point to accept the manipulation or Reset.


5. In some cases, you can repeat the manipulation.



You can Reset to halt a fence manipulation that is in progress. Manipulations that were completed before Resetting remain in the design and can be undone. (Pressing <CTRL-C> also halts a fence manipulation.)

Manipulations on many elements

Some fence manipulations on many elements (large arrays, for example) may take a long time to complete.

To minimize potential problems, do the following before attempting such a manipulation:

• Back up the DGN file (see To make a backup copy of the active DGN file).

Optimized fence clipping

The Optimized Fence Clipping preference in the Operation category of the Preferences dialog box is on by default. This preference enables you to maintain closed shapes, solids, and surfaces when clipping those elements that cross the fence boundary. If this preference is turned off, closed shapes, solids, and surfaces are dropped to linear elements when clipped.

Click here for more information on the Operation category of the Preferences dialog box.

MicroStation's ability to place fences with as many as 5000 vertices provides tremendous flexibility when performing clipping operations.

You can also use this preference in conjunction with the Locate By Face preference (in the Input category of the Preferences dialog box) to create associative holes in closed shapes, solids and surfaces. When Locate By Face is set to Always, fences that are located entirely within a closed piece of geometry can perform clip actions upon their section of the larger area.

To create an associative hole inside an element using optimized fence clipping

1. From the Workspace menu, choose Preferences.
   The Preferences dialog box opens.


2. In the Input category, set Locate By Face to Always.


3. Click OK to accept the change and close the dialog box.


4. Select the Place Fence tool.


5. Set the Mode to Clip.


6. Inside a closed shape, solid or surface, place a fence.


7. Select the Delete Fence Contents


8. Accept.



To keep fence clipping from changing the larger geometry in which it is placed, set Locate By Picking Faces to Never or Render Views Only.

Special fence manipulations

The Manipulate Fence Contents tool can be used to “stretch” (extend or shorten) segments of elements that overlap the fence. It does this simply by moving element vertices that fall within the fence. You can also stretch elements that overlap the fence using the Copy tool, Move tool, Scale tool and Rotate tool.

The fence contents can also be moved or copied to a new DGN file.

To copy the fence contents to a new DGN file

1. In the Key-in window, key in FENCE FILE or FF=.
   The Save Fence Contents As dialog box opens.


2. Key in the name of the new file and set the directory in which it is to be created.


3. Click the OK button.


4. Accept the copy.

Alternative Method — To copy the fence contents to a new DGN file

1. In the Key-in window, key in FENCE FILE <filename> or FF=<filename>.


2. Accept the copy.
   The file is created in the directory that is pointed to by the MS_DEF configuration variable.

When using the second method, if a file already exists with the specified filename, an alert box warns you that it will be overwritten.

To move the fence contents to a new DGN file

1. In the Key-in window, key in FENCE SEPARATE or SF=.
   The Save Fence Contents As dialog box opens.


2. Key in the name of the new file and set the directory in which to create it.


3. Click the OK button.


4. Accept the move.

Alternative Method — To move the fence contents to a new DGN file

1. In the Key-in window, key in FENCE SEPARATE <filename> or SF=<filename>.


2. Accept the move.
   The file is created in the directory that is pointed to by the MS_DEF configuration variable.

When using the second method, if a file already exists with the specified filename, an alert box warns you that it will be overwritten.