MicroStation PowerDraft CONNECT Edition Help

Variables and Variations

Variables are named values defined within a model, which can be used to drive the model's geometry parametrically by associating variables with dimensional constraints and element properties. When the value of the variable changes, the value propagates to associated dimensions or element properties, causing the geometry to update. Variables can be defined in two ways:
  1. By attaching an Item Type from within the Variables dialog. The properties of the Item Type become available for use as variables. Item Types can be defined in the Item Types dialog.
  2. By defining local variables. Local variables are defined directly within the Variables dialog and are specific to a single model, rather than being part of a general-purpose Item Type. They are useful for defining temporary or construction variables which drive geometry but are not necessarily considered integral properties of the object being modeled.
Note: Property definition names of an item type which you want to attach and the local variable names shouldn't be same.

Variations are named sets of variable values. Each Variation specifies a value for every Variable defined in the model. A Variation can be applied to the model such that the "active" values of the model's Variables are updated to reflect the values specified by the Variation. A Variation can also be selected when placing a parametric cell, such that the parametric cell's variables obtain their values from the values specified by the Variation.

Variable Driven Modeling and Constraints

When adding a constraint to a feature, you can bind the dimensional value to a variable. When variables are used in this way, you can "redesign" the element simply by changing the active values of the model's variables. This results in the element being regenerated with the new values applied to the constraints for the features. Similar effects can be achieved by binding the value of an element property to a variable. To constrain to the assigned variable value, you can select the available variables from the drop-down menu that appears in the value field while applying the constraint.

Variables and Parametric Cells

While placing a model as a parametric cell, you can choose which variables and variations to use to define the cell. To enable the placement of a model as a parametric cell, you must set the model’s Can be placed as Cell property to True and its Cell Type to Parametric, in the model's Properties dialog.
Note: A model which has variables or variations but does not meet these requirements cannot be placed as a parametric cell. A model which meets these requirements, can be placed as a parametric cell regardless of whether or not it defines variables or variations. But useful parametric cells usually define either or both.
The variables of a placed parametric cell can be fixed (not editable) or free (editable) depending on the Scope setting set in the Variables dialog. Also, the visibility of the variables of a model placed as a cell, can be controlled with the Display setting in the Variables dialog. Typically, intermediate variables which are used to generate geometry but are not considered useful outward properties of the object being modeled should be set as Hidden.

Set Scope to Instance, if you want the variable editable after placing the cell | Set Scope to Definition if you want the variable to be fixed.

Remapping Variables and Variations - If you try to delete a variable that has been referenced in an element, Confirm Delete dialog opens. You can choose to remap the reference to another available variable, as below:

If (None) is selected (default), you will lose all the references to that variable.
Typically, you would want to update a cell definition when the cell model changes in one or more of the following ways:
  • Added/removed variables
  • Added/removed variations
  • Changed the geometry within the model
Let us take a scenario where you had a Door model, placed it as a cell, then you (or the administrator in your organization responsible for maintaining cell libraries you use) edited the original model to include a knob and maybe added a variable which controls the knob offset. In this situation, you can update your cell definition (and cell elements) to reflect these changes by using Update Parametric Cell dialog. This dialog will help you remap the variables and variations of the outdated wooden plank model to that of the updated door model as below: