March 9, 2014

BIM math

An interesting equasion surfaced this last week:

B + I(fc) + M = BIM.

The whole debate started with the release of Sketchup 2014. One of the major new features (and certainly the one that caught the most attention) is that Sketchup now has support for IFC. And other data schemes such as COBie or anything you come up with yourself.
And because of the support of IFC, Sketchup now surely qualifies for the term "BIM".
In other words: a Building Model that works with IFC automatically constitutes BIM. Let's try some logical reasoning here.

Step 1: a Model.

We can all agree that for BIM to take affect, there needs to be a Model of some sort. We can also agree that any 3D modeller, including Sketchup, is capable of creating a Model.

Step 2: an Information Model.

Ok, just a random dumb representation of reality does not constitute BIM. If it would, the LEGO Architecture sets would constitute BIM, since those are models too. So at some point Information needs to be added to the mix.
Here's how:
1. There's data in a Model: all geometric and non-geometric properties of any objects inside the Model or the Model as a whole. By creating a Model the author by definition adds this data.
2. This data will become information at that point in time when the data is reused. Data that is not reused, cannot be classified as information. Why not? Because the concept of information implies a sender AND a receiver. Information is useful data. How can it be useful if it cannot be used?
3. An Information Model therefor is a Model containing reusable data.
Does Sketchup create Information Models? Well, yes. It does. You can create a Model (step 1), which has geometrical data, and then add some more non-geometrical data (IFC or COBie data for instance). Exporting this to IFC means this data can be received and reused by someone else. Which means we now have an Information Model.

Step 3: a Building Information Model.

Up until the moment I learned about Sketchup's new IFC feature I took this "Building"-part for granted. Whether it's the noun or verb, off course we're talking about Building(s). We're in the AEC sector right?
However, the Sketchup claim to BIM made me realize something: the term "Building" does not just specify our trade. It also applies a logical connection between Model components that add up to more then a sum of all parts.

Translated into real-world scenario:
Buying all your bricks, concrete, steelwork, ducts, pipes, doors, windows, and all other parts of a building does not actually give you a building. Randomly tossing them on the construction site does not either. They have to be processed in a certain order and specific way to actually form a building together. By doing so, you not only have the components themselves but also the interaction between those components that create the actual building.

Same goes for the digital representation: BIM is not about having all the components floating around somewhere, nor is it about having all kinds of information attached to those components. What sets BIM apart from just information-enriched models is the fact that these components have relationships, a (rudimentary) awareness of their surroundings. And can interact with them.

And, regrettably, that's where Sketchup falls short at the moment. The SU engine does not have the ability to let components have a relationship, a hierarchy between each other and with the project as a whole. Which means that there is no such thing as a Building Information Model possible. The SU export to IFC can classify components in the IFC scheme, but as far as I can tell at this point, it's not able to establish hierarchy between components (Window > Wall > Building Storey > Bulding > Site > Project). Which makes it a non-valid IFC (the hierarchy is mandatory!), and worse: not a BIM. Sketchup's interpretation of IFC is a classification system. Nothing more, nothing less.

Does this render IFC in Sketchup useless?

Well no, off course not. Having the ability to map and export to IFC is a huge interoperability improvement. Having the ability to add information and export that is awesome. Imho, it takes Sketchup from a Modeller to an Information Modeller. Just don't count on it being an acceptable BIM. 

Will there ever be Sketchup BIM?

Why not...? All they have to do is embed a form of hierarchy in their modelling engine. However, this might just be the most challenging task possible. We all know that more hierarchy and relationships mean more constraints. More constraints mean less intuitive modelling. And wasn't just that generally considered SU's best feature?

The question is: why would they? What's wrong with just having a freeform modeller to quickly conceptualize design ideas? Why does that *need* to be BIM? After all, some of the most BIM-minded architects I know still use hand sketches in the earliest stages of design to channel their creative thoughts with a speed and flexibility no BIM software could achieve (in the near future). And they all use Sketchup as a digital representation of this thought-process.

And I'm wondering: why would Trimble want to move so eagerly into the realm of "real" BIM software, where they will just be one of the guys, while they now have a tool far superior for it's specific task?


  1. SketchUp does include a notion of hierarchy through a system of groups (simple hierarchical nesting) and components (groups with multiple linked instances of a common definition) and so I would argue that it is A bit more capable yet than you describe. But no matter- I think you're really getting close to the roots of a much more universal system of information modeling that we're accustomed to talking about in the popular BIM discourse.

    People tend to describe SketchUp in terms of it's "lacks" (as in "SketchUp lacks a parametric wall tool.") though we have for years resisted adding such features. Our goal is to develop a simple tool through which designers can express ideas of great complexity. The pencil is my greatest inspiration.

    Which kind of makes me wonder... couldn't you implement a BIM system (using your definitions) using only pencil and paper?

  2. For completeness, here's my blog post on the subject:

  3. Martijn, a hierarchy is not flexible and complete enough to represent a building. Building components have richer and more interdependent relationships than that. This is why clashes occur - they are the collision of elements that are only aware of their own hierarchy. A graph is probably a more realistic representation of the relationships between elements.

  4. Interesting ideas. I totally applaud that SketchUp wants to play nice in a BIM workflow, yet retain its strengths. The IFC models from SketchUp are already more usable e.g. By loading them in Solibri. Would be interesting if initiatives like OpenStudio will start to utilize this approach. Right now, many SkeychUp enhancements occur in isolation and the classification options might help with that.

  5. I do like that Sketchup supports IFC but for a real discussion about how useful and well-structured the export data is for fabrication and construction, why not compare Tekla and Sketchup since they are both owned by Trimble? And don't only include architects in the conversation, engage with the engineers of real buildings as well as fabricators, builders and sub contractors with experience using this data on real projects. There is so much more to BIM than form finding and then sharing the data as 2D pdfs with the people who actually engineer and construct buildings.

    We are working to encourage this kind of collaboration in our not-for-profit Digital Fabrication Network And we hacked IFC data and new and creative ways at our AEC Hackathon on Facebook campus again last month. Website here
    Videos of the hacks here