Display Rules Series Part 1: Thematic Mapping

Display Rules are a powerful feature found within the MicroStation CONNECT Edition in which the display of engineering models can be overridden based on a number of criteria.  Typically, display rules will key-off of elements symbology such as level or color.  Or item values such as area or capacity.  But, display rules can also access file, model, reference, and other properties.

Now, display rules don't actually change the symbology of the model.  They are strictly for display time.  However, the results can be printed PDF and other formats.

As a demonstration of the powerful capabilities that display rules can offer, here we will assume the role as a Mapping designer.  As a designer, we might want to create a map that illustrates population density.  In this case, the population density for the state of Florida, by County.

In this example, we have MicroStation vector data representing the outline for the state of Florida and neighboring states, as well.  In addition, we also have an attached GIS data reference in the form of a Shapefile.  This Shapefile portrays the county boundaries of the United States, Puerto Rico, and the U.S. Virgin Islands, by showing the counties as areas.  In this design file, this reference has been clipped to the vector boundary of Florida.

As part of the Shapefile reference, one of the properties is the 2006 Census data produced by the U.S. Census Bureau.  We want to expose this data through the creation of a display rule and thereby creating a population thematic map.

To create a new display based on the county population data of Florida, we’ll begin by opening the Display Styles dialog from the View Attributes dialog.  From the Display Styles dialog, we’ll go ahead and create a new display style and specify a name.  Here we’ll call it, County Population.  Once the new display style is created, we’ll go ahead and double-click it to make it the active display style.

Next, we’ll open the Display Rules Editor by clicking the Display Rules icon next to the Display Rules drop-down list.

The Display Rules Editor is used to create and manage display rule sets and display rules for display styles.  From here, we’ll click the New Display Rule Set icon. The display rule set appears in the display rule set list box, where you can give it a name.  We’ll call this, County Population.

So far, we have created the County Population display style and the County Population display rule set.  In order to create our thematic map, these two must be associated.  To do this, from the Display Styles dialog, we can select the County Population display rule from the Display Rules drop-down menu.

Then after this, we need to return to the Display Rules dialog.  Here, we will click the New Display Rule icon to create a new display rule for the selected display rule set. The rule appears in the display rules list box, where you can modify the rule.  Clicking on the condition, in this case, Applies Always, will thereby open the Condition Editor.

You can create conditions in the Condition Editor dialog. The conditions can be comparing a property with a value or comparing one property with another property.

You can select a property from the picker next to the icon.  Clicking the drop-down list opens the following host property types:

  • Element - Contains properties of elements or associated items such as element color, area, thickness, and so on.
  • View - Contains properties of the view or associated items such as display style, camera position, view index, and so on.
  • Model - Contains model or associated item properties such as model name, description, annotation scale, and so on.
  • Reference - Contains reference or associated item properties such as reference attachment file name, model name, level, and so on.
  • File - Contains file or associated item properties such as file name, file size, revision number, and so on.

In this case, we would like to expand the “County Data” item type, and then select the “POP” item property.  This is the population data from the attached Shapefile.

Next, we’ll set the Comparison Operator to Less Than and set the value against which the property will be compared to 20000.

The description for a condition is automatically generated from the conditions that you create. You can override the description in the Description field of the Condition Editor dialog to make it more understandable.  For this description we’ll key-in, County population - less than 20,000.  Clicking OK will set the condition and return you to the Display Rules dialog.

You can assign one or more actions to display rules. These actions are executed if the set conditions are met for the display rules.

Clicking Add or remove display rules actions (green-plus icon) displays the following action options:

  • Hide Element
  • Symbology Overrides
  • Element Priority
  • Display Style Override
  • Hatch Area

In this case, we want to select the Symbology Overrides option.  Once selected, a preview now appears under the Actions column.  Selecting the preview opens a window, allowing you to set the symbology overrides with the following options:

  • Element Color Override
  • Fill Color Override
  • Line Style Override
  • Line Weight Override
  • Element Transparency Override

Here we will select the Fill Color Override option and set the appropriate rgb value (58,171,1).  Clicking away from this window will close it.

Upon closing the Symbology Override window, immediately within the view, you see that the condition was met.  As a result, counties with less than 20,000 people are now displaying a green colored fill.

So, this will complete the first rule for the County Population rule set.  To complete this example, we need to create four more rules to the set to accommodate the categories for the population ranges.  As such, we’ll create the second rule as we did the first one by first selecting the “POP” item property from the “County Data” item type.

This time, however, we’ll set the Comparison Operator to, Greater Than, and set the value against which the property will be compared to 20001.  In order to achieve the population range, we must click the, Add new criterion (green-plus icon).  Here we’ll set the first Comparison Operator to, And, select the “POP” item property, set the second Comparison Operator to, Less Than, and set the value to 50000. 

Like before, the second rule will be the Fill Color Override option and with the rgb value 137,211,0.  Finally, we’ll give the description, County population - 20,001 to 50,000, click OK to finish the second rule.

Rules 3 and 4 will be similar in setup to rule 2.  Rule 5 will similar to Rule 1, as shown here in this table:

And as a result, here is the completed County Population rule set.

In this demonstration, the County Population display rule set and the associated County Population display rule were created in the active dgn file.  As a good practice, new display rule sets and display styles can be stored in the DGN Libraries for easy sharing to all project participants.

There are many advantages to leveraging display rules as part of your workflows.  One such case could be that you are a Civil Designer and there are times when you may need to review and visualize the Terrain model. Display rules could be generated as an effective means to display changes in elevation or slope.

Another might be for an Architectural Designer who might want to create a display based on the material type, as an example.  Perhaps produce a drawing that shows where the expected floor treatments are to be placed.  This display could immediately show where the correct/incorrect floor treatment were assigned.  Another possibility would be for quality control.

And the possibilities go on and on.  In the next part of this Blog series, we’ll take a look at some other examples and workflows for utilizing Display Rules.

If you would like to try recreating the thematic map as discussed here, you can download the Florida Master Map.dgn file attached here.  It is a single, self-contained file.  The Shapefile was merged for simplicity sake.  The counties still contain their respective item data.

Florida Master Map.dgn