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MicroStation

MicroStation V8's Models

4 Jan, 2004 By: James Dyer

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This month's column focuses on the powerful model concept found in MicroStation V8. Our design and engineering projects are increasing in complexity and evolving from task-based design activities to interdisciplinary activities. Being able to compile project-level information within a single MicroStation session allows you to be more efficient and effective in your daily activities.

Models
MicroStation V8 users are no doubt familiar with its new models support. Models are a fundamental vehicle for organizing your design data and drawing data. Design models correspond to the way you store design data in pre-V8 MicroStation. V8 adds sheet models, which you can use to compose or otherwise document the design model.

Related to models is the way cells and cell libraries are organized. Now, instead of the unique file structure found in cell libraries of the past, MicroStation V8's cell libraries share exactly the same models organization as a normal design file.

To explore further, let's compare V8 with previous versions of MicroStation. All elements in MicroStation/J and earlier share the same design coordinate "world." This means that when you draw a line at a specific coordinate location and then draw a circle at the same location, the two elements share the same design space in MicroStation. Regardless of what levels you put them on, they share the same coordinate space.

In MicroStation V8, models introduce an entirely new approach. When you set up a DGN file in MicroStation V8, you create at least one model within your new DGN, whether you know it or not.

Figure 1. Working units dialog box.

This model has several unique properties. First, the coordinate space you define using the familiar Settings / Design File / Working Units dialog box is unique to the model (figure 1). If you never create another model within the DGN, there is no apparent difference in operation over previous versions of MicroStation.

The fun begins when you use the Model Manager (File / Models) to create additional models within a DGN file. When you open this dialog box for the first time, only the single Default model is listed. Adding a second model is easy. Click on the Create New Model icon, enter the name of your new model, and select OK (figure 2). Voila, you've created two completely separate models within the same DGN.

Figure 2. Use Create New Model to add another model to your DGN file.

MicroStation provides the name of the active model by appending the model name to the file name in the title bar.

Another indication that you've changed from one model to another are the views themselves. Every model has its own set of eight views. The model whose views are displayed or available for display at a given time is the active model. When you switch from one model to another model, the content presented in the views is automatically adjusted. This can be a bit disconcerting at first, especially if your DGN has a lot of existing design data in it. No need to worry, though - your drawing is safe. It simply isn't found in your current model. Double-click on the previous model, and the contents instantly reappear.

View groups
In MicroStation V8 you can package views into view groups. View groups are separate collections of views that you can define for different purposes. Each view group is associated to only one model; thus when you initially create your second model, a view group of the same name (with "Views" appended to it) is automatically created and activated when you open the model. To switch between the models, you simply double-click on the model name in the Models dialog box or select a view group associated with the desired model.

The ability to have multiple models within one MicroStation DGN file opens a world of possibilities. When you initially create a new model, you set the type of use for that model. In MicroStation V8, there are two types: Design and Sheet. Their names give away their intended function. By default, the design type of model is intended for creating design geometry, usually at full scale. The sheet type of model is more appropriate for creating traditional paper drawings where you set a scale for design data.

For those who prefer the keyboard, you can type in:

MODEL CREATE DESIGN <NAME> <DESCRIPTION>
MODEL CREATE SHEET <NAME> <DESCRIPTION>

When you work with DWG files, model space is presented within a design model and paper space is presented within a sheet model. The DWG file format allows one model and unlimited drawing layouts. When you are working with models in a DGN file that you plan to save to a DWG file, the easiest way to ensure compatibility is to use only one design model with unlimited sheet models.

Figure 3. Cell library.

Models can be either 2D or 3D and can also be placed in a design session as a cell. Therefore, any cell library (*.cel) can be opened in MicroStation as if it were a DGN, and you are be presented with multiple models without the pain of multiple scales and units because in MicroStation V8, all designs are created at 1:1 scale (figure 3).

The power of models really expands when used together with MicroStation's reference system. As with previous versions of MicroStation, reference attachments are stored in the DGN file just like a line or an arc. This means each model has its own reference attachments. When you attach a reference, one of the new parameters you set is the model to access as part of the reference definition. With models, you can develop several sheet models that all reference the same design model. In fact, you are not restricted to having only one such design model.

Until next time - enjoy MicroStation!