101 - An overview of using cells

What is a Cell Library?

Cell libraries are .DGN files only with the .CEL suffix. The file format is identical. You can open a cell library just like any other design file. This means that a cell library can be edited simply by opening it.

This is where Models come in. All DGN files contain models (the term model means different things in different contexts!), at least one design model called default and one or more other models that may be design, drawing or sheet models. The Cell library is a .DGN file containing an empty default design model and one named design model per cell. The Model’s name and description populate the list in the cell library dialog.

Creating cells can be done most easily using the Create Cell process: place fence around or select the elements that will be in the cell; place the cell origin; click the create button (see below for details). This is still the quickest way to create cells. The origin of the cell is the 0,0 point in the model. If you wish to move the origin of the cell the geometry in the model needs to be moved relative to the 0,0 point.

Editing cells can then be done in the .cell file just like editing any other MicroStation data.

When creating cells keep them simple, especially when importing manufacturers information. Manufacturers will draw their cells at 1:1 detail so every tiny curve or radius will be drawn, it may be worth simplifying these.

Cell Library Locations:

In the Cell dialog, the pop-down list should be gathered from your project cells folder:

e.g. ….\jobs\99999_Training Only\Resources\*.cel

and then from the standard workspace:


Your project cell library is for your own use on your project. You can create specific cells for your own project and/or import cells from other cell libraries. You can create and edit cell libraries in the project cells folder, you can only read the standard cell libraries in the workspace.

The Difference Between Cells And References:

The functionality offered by Models blurs the distinction between Cells and References. There is however, one very clear difference that will help you to decide which to use in a given context.

For instance:

If you want to create a room layout but have not completed the design or do not know what fittings are required, you could create a draft layout in your cell library, place it in the drawings. As the design progresses the cell library can be edited. When the room layout data is ready for issue the existing cells in your drawings can then be updated. These would then contain the latest version of the cells.

If this was done using references, the drawings into which the room layouts were referenced would update in an uncontrolled manner as work on the room layouts progressed.

In other situations you would want to have the latest state of referenced information.

Shared Cells

If a cell contains many elements placing a lot of them can increase file size significantly reducing performance. To avoid this share large cells in the design file. (Note, if you are familiar with AutoCAD, this is the only way AutoCAD handles cells.)

A Shared Cell is stored within the Design File. There is one Shared Cell Definition and then each subsequent placement is an Instance of the Shared Cell that refers to the Definition. The benefit of Shared Cells is that they save space in a file, if there are many

Instances of a Shared Cell each Instance only occupies a tiny part of the file being simply a pointer to the Definition elsewhere in the file.

Shared Cells can be updated quickly, replace the Definition and all Instances will update.

It is possible for Shared Cell Definitions to accumulate in a file, especially if the file originated from AutoCAD. To remove unwanted Shared Cells go to the Key-in window (Help > Key-in) and enter delete scdefs all. To save doing this manually set your Preferences to Compress on Exit.

When in doubt, to see if any Shared Cells remain, open the Cells dialog, tick the Use Shared Cells box and see what is listed.

Shared Cells can also be deleted individually by selecting them in the Cells Dialog and clicking the Delete button at the lower right. Be sure that you are selecting the correct cell before deletion. If the shared cell has been placed somewhere in the file a warning dialog will tell you that it cannot be deleted.

Create A Cell Library:

1. Open the Cells dialog, File menu > New…

2. Browse to the folder where you want the library to be created, normally your project resources folder

3. Give it a name that includes your project code.

Create A Cell:

1. Draw everything that you want to be included in the cell (remembering that it is easy to edit later if the cell contents are still being designed).

2. Attach the cell library that you want the cell to be added to

3. Either place a fence around the elements or select the elements to be included. Use whichever method that you are happy with. Note that when selecting elements be sure that there are no existing selections!

4. Use the Define Cell Origin tool to define the origin of your cell,

snap the marker onto the appropriate point.

5. Click the Create button

Enter the cell name and description, try to keep these logical and consistent with each other so they sort sensibly.

How To Import Cells Into Cell Libraries:

Open a cell library that you have editing rights to.

Open the Models dialog, File > Models or use the Models icon in the Primary Toolbox.

Click the Import Models icon and browse to the Cell Library (.cel) or DGN file that you wish to import a model from.

Click OK and then from the Select Models dialog select the model(s) that you want to import and click OK.

That's it!

Using this process you can build your own cell library for a job containing cells from any other library or design file.

It is also possible to import from DWG files but you may need help to set up remap files to ensure that the imported data arrives on the correct standard levels.

Levels in Cells:

The levels that cells are placed upon are affected by the level they are drawn on in the library:


Note how elements placed on the Default level in a cell will adopt the active level when placed.

The top cell has text on the levels shown



The middle cell has text placed on the Default level


The bottom cell has text placed on A-Z000-T-Anno and the Default level.

The cell elements originally placed on the Default level have all adopted the active level A-G23-G-Strs.

It is most often useful for pattern cells to adopt the active level, so they should be drawn on the default level. Sanitaryware or furniture should always be on the appropriate level so draw/import them to the appropriate levels. The levels of whole cells or individual elements within cells can be changed if necessary.

Update or Replace Cells

If a cell needs to be updated as the design develops, the Replace Cell tool can be used to change cells already placed in a design to the new version.

This tool has a range of options:

When the update Method is selected, provided that the cell library containing the cell to be replaced is in your standards\cell or project cells folder, all you need to do is select the cell for it to be updated.

Mode can be set to Single or, if all the cells in the current Design Model need to be updated, to Global.

To replace one cell with another set the Method to Replace:

the choices are then:

  • Identify the cell to be replaced then choose another cell in the same design Model to replace it with
  • Use the Active Cell, the 'Browse Cells' button can be used to select the cell that you wish to use for replacement.

If the cell to be updated contains tags whose content should not be replaced, leave 'Replace tags' unticked. Obviously if the replacement cell does not contain the relevant tags they tag content will be lost.

Note: if a shared cell is updated or replaced all instances of the shared cell will be changed.

Further details are available in MicroStation help