One of the first issues a new user, particularly a landscape architect, might encounter in Revit is the general lack of control. How do you control the graphics? How do you get the results that you want? It can be a bit overwhelming. Understanding Categories and Subcategories is the first part of controlling the model (and thus graphics) and they are also critical for exporting and sharing your data properly.
Categories are the different types of Families within Revit. Each Family Category has different properties and parameters. The Main Categories are hardwired into Revit; they cannot be renamed, created, or deleted. But within the Categories there are Subcategories. Some of these are hardwired (again, cannot be deleted) but you can create as many Subcategories (Subcats) as you want and delete the unnecessary ones.
In the 2015 Architectural Template, the Site Category has 8 Subcategories, but only Hidden Lines, Pads, Project Base Point, and Survey Point are necessary.
In a Project
From a Project file, Subcategories can be created and modified in Object Styles (on the Manage ribbon or at the bottom of the Visibility/Graphic Overrides dialogue).
Once added in Object Styles, they will appear in the Visibility/Graphic Overrides for every View, allowing you to override them accordingly. For System Families (such as Floors), Subcategories can only be applied to In-Place Families (such as Curbs). But when working with Loadable Families, there are a few more things you’ll need to know…
In a Family
From a Family file, Subcategories are also under Object Styles, on the Manage ribbon.
Once added, Revit generates a new projection and cut line for the Subcategory.
It also creates a Subcategory that can be applied to Solid forms. The default Subcategory (None) assigns the solid to the main Category (which in this example is Site).
Things get a little trickier with nested Families, especially if they are different Categories, such as Detail Items (Detail Components).
If a Subcategory does not exist in a Project (but it is in a Family), that Subcategory will automatically be created when the Family is first loaded into the Project.
Export Settings (dwg & IFC)
In addition to providing graphical control, Subcategories are necessary for controlling how the model gets exported to dwg and IFC. Both export options allow you to reassign either Layers or IFC Classes based on the available Subcats.
For more information about exporting to dwg, check out Export Settings for DWG.