Making the Cut

I'd like to maintain my momentum today and continue our discussion on Volumes in Revit MEP 2009.  We've been discussing best practices for their creation, and today we are going to explain an important concept for Volumes, the Calculation Height.

We've spoken previously, and highlighted in the Building Performance Analysis in Revit White Paper how we extrude Room Volumes vertically until we hit the Upper Limit of the Room or we hit a Bounding Element.  Spaces in Revit MEP 2009 have the same behavior.  What defines the Cross-Section of that vertical extrusion?

The answer is the Room's Perimeter, which is defined by the Bounding Elements that make up the Circuit around the Room in a Plan View.  What happens if those bounding elements are slanted in different directions?  Well the Cross Section will change as you move vertically from the floor.

The thing in Revit that defines the height that Cross-Section area is cut is the Calculation Height.  In previous releases there was a global project setting in the Room and Area Settings... dialog that allowed for Automatic calculation or an explicitly defined height.  Those choices still exist in 2009, but now are applied on the Level Type, rather than a global project setting.

What does that all mean to you?  Well if you deal with complex geometries in your Architectural Models in Revit, then it will mean a whole lot.  Let's explain the concept in a video.

Calculation Height on Level Types

I hope that all makes sense to you all.  We'll continue this topic tomorrow and examine how we can leverage this new behavior to handle some complex Architectural forms.