Thursday, March 31, 2011

Revit - Understanding Parameters

I recently replied to a post on AUGI regarding parameters in Revit and the difference between the types, I realised I was yet to write about this and as a result, I bring you the post below. Hopefully after reading, you will have a better understanding of parameters, and how you can gain from the use of shared parameters in your projects.

Definitions;


Parameter

Is a setting that determines the appearance or behaviour of an element, type, or view.

Project Parameters
Are user-defined fields that you add to multiple categories of elements, sheets, or views in a project. These parameters are specific to the project and cannot be shared with other projects. For example: You can create a project parameter named “Approved By” for views. In the properties for each view you can enter a value for this parameter to indicate who approved the view. You can use a project parameter in multi-category or single-category schedules. However, you cannot use project parameters in tags for model elements.


Family Parameters

Are user-defined fields that you add to families. They are stored in the family file, and cannot be used in any other element or environment apart from the family it was created in.


Shared Parameters

Are user-defined fields that you add to families or projects and then share with other families and projects. They are stored in a file independently of the family file or Revit project; this allows you to access the file from different families or projects. In addition, shared parameters can be used in tags for model elements, and they can display in schedules.


Type Parameters

Are settings that control the appearance or behaviour of all elements of a particular family type. Type parameters are common to many elements in a family. A type parameter affects all instances (individual elements) of that family in the project and any future instances that you place in the project.


Instance Parameters

Are settings that control the appearance or behaviour of an individual element in a project. The instance parameters and type parameters of an element combine to establish its element properties. Instance parameters can vary with the location of an element in a building or project. An instance property affects only one selected element, or the element that you are about to place. For example: Suppose that you select a beam and click (Element Properties). You change one of the instance parameters and click OK. Only that beam is affected, even if the project contains other instances (individual beams) of the same type.

Another example: The dimensions of a window are type parameters, while its elevation from the level is an instance parameter. Similarly, cross-sectional dimensions of a beam are type parameter, while beam length is an instance parameter.

In terms of what type of parameter to use when, that all comes down to what you want to use that parameter for.

For example: If you are creating a structural connection family, let's say a simple face based plate, you will add parameters for the dimensions of the plate, length, width, thickness. If you use a family parameter for this, the parameters will flex, and do everything that a shared parameter will do apart from one key thing, a family parameter cannot be used anywhere else but in the family where it is created. If you were to use a shared parameter instead, these parameters can be scheduled, and because the parameters are stored in your company shared parameter .txt file, they can be used on future structural connection families you create. You can now create a structural connection schedule and add these shared parameters to the schedule.


You can also add these to a custom made structural connection tag. The tag will automatically read the dimensions of the plate, and with appropriate prefix / suffix details in the tag, this can make annotating steelwork details extremely quick.


Below - The element properties for the plate above, showing the information the tag is using from the model element.


Below - the shared parameters added to the label in the structural connection tag, with appropriate prefix / suffix where required.

Shared parameters are powerful, and part of the concept of using the 'information' from the Revit model.

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