BIM: Split vs. Merged Models

1 Nov

As we move to BIM, architects need to acquire new skills, particularly in the area of information systems. In school, magazines, and competitions, images are what matter – design is king. Design will always be important, but we are in an information age of architecture. BIM, Energy Modeling, and Form Finding using Scripts are the new architecture. Databases have become a tool of the trade and I fear that architects are lacking in their knowledge of them – if you refer to an Excel spreadsheet as a database, you are lacking. I am not advocating that architects become programmers and information systems experts, but I am suggesting that without at least basic skills you will fall behind. AutoCAD has had a LISP environment since 1986 yet the majority of architects I know would tell you that LISP is a speech impediment. How little knowledge we have of our tools. It’s like using a pencil but ignoring the eraser on the end and starting over whenever you make a mistake.

 

My interest today and the reason for this post is to offer my two cents on the difference between split and merged models.

 

Simply put, a merged model is a model with geometry and data combined. This would be a Revit model where all the data about the objects – rooms, walls, doors – exist in the model. This is the model type that Revit leads you toward. And what happens when you embed large amounts of data in to Revit? Your file size becomes massive and performance takes a hit. For what? So that you can create a schedule later or to color code a floor plan? What if you need this data for something else? Are you going to export it to CSV every time you need it? What about a client? Are they going to need Revit to update the information about their building?

 

A split model, on the other hand, is where the geometry and the data are in different systems. The geometry is in your Revit model and the data is in a database – SQL Server or MySQL. A split model is superior to a merged model and this is what we should be aiming for.

 

There are certain pieces of data that will always be in Revit. The area of a room or a wall should be determined by the geometry, not entered in a database. But the overriding point is that the model should have the geometry and an ID for each object. That is all. You should have a database with tables for Walls and Rooms and these tables should have an ID and the rest of the data – use, type, department, fire rating, load bearing.

 

So how do we create schedules and create fancy color coded plans without the data? We use a JOIN and connect the tables of data to the geometry based on the ID.

 

The data about our building will change far more often than the building. Painting walls, replacing doors or carpeting can be updated in a database. The model only needs to be updated when something is added – an addition – or removed – demolition.

 

Another reason for split models is that we should keep our tools separate. Do you really need a 3D modeling application to also be a full blown database application? No. We only need the ability to connect them. Let Revit do what it does best – model.

 

Planners use split models in GIS, programmers use a Model-View-Controller framework and web developers have been working to remove the code and logic from the design of web pages for years. This is nothing new. Architects need to look at how other professions have solved this problem and learn from their best practices. I remember a quote from an officer in the Coast Guard that went something like this: “The data about our buildings is worth more than the buildings themselves.”

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2 Responses to “BIM: Split vs. Merged Models”

  1. Jean-Claude Vandonghen June 7, 2013 at 9:48 am #

    For those who read French, here is a good explanation of BIM – IFC : http://www.rhino4you.com/1/bim_ifc_maquette_3d_383350.html, and what the French call the digital model/sketchup/mockup (maquette numérique).

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  1. What Should Revit Be? « Architecture and Planning - November 2, 2012

    […] alluded to the answer in “BIM: Split vs Merged Models.” Revit should not be what I think this commenter wants it to be – all things. I hear […]

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