Parametric Thinking and Pandora

Careful . . . I haven't really thought this through entirely but here goes:

You're having guests and you're putting music on via Pandora. You think, something a little folksy, simple, a little gritty. Bob Dylan before he went electric! So you pop on a new station for Bob and 15 minutes later, you're wondering why you're listening to the Traveling Wilbury's and Credence Clearwater Revival, and all that stuff from Stealer Wheels. Well, you asked for something really general and you're going to get something really general. It's all Dylanesque, the problem is, which Dylan did you mean?

Pandora is a system, not a DJ or a librarian, and like any other system, it isn't going to be any smarter than the information you give it. I don't know technically how it works, but it seems to work in some derivative fashion. You give it Bob Dylan, and it will give you back music that was inspired by Bob or very near to him in musical time/space, which is a pretty large patch of musical history. To get effective playlists, you have to go one step back or above your target.

I've heard a lot of questions from Revit users about why it doesn't do what they intended. Yes, sometimes there are bugs. But more often than not, the problem is that Revit is not yet telepathic (fingers crossed for 2012!) and the user has not given the system enough information to properly define the performance of their geometry. One user was confused about the behavior of an arch that was "defined" by two points (center and radius). An arch must have three points to be defined (arc length or angle!), otherwise you get "Stuck in the middle with you" or "The Joker".

If you want the gritty/soulful/folksy Dylan, don't ask for Dylan. When he's doing that sort of music, he's inspired by Woody Guthrie. So if you put in Woody Guthrie, you get Woody and all the music that is derived from and lateral to him. Generally I have found that this is how Pandora works. You need to ask for something slightly more ideal than you want to hear. If you ask for Woody, you get Leadbelly, the early Johnny Cash, lots of fantastic hillbillies that you've never heard of plunking on banjos (or at least I haven't), and pre-Royal Albert Hall Dylan. (BTW, Don't even try putting in "Johnny Cash".)

Parametric design is the same way. You need to identify the underlying principles that you are after. You want a curvy thing . . . what kind of curvy thing? An ellipse, an arc, a spline? In particular instances they can all look almost identical, change the context and they diverge greatly. Dylan's "Knockin' on Heaven's door" can quickly become Guns n' Roses "Knockin' on Heaven's Door". Iy, iy, iy-yi-yi.

You can of course define geometry in a sculptural manner. This is totally valid, but don't expect it to be dynamic or rapidly reconfigurable. Sculptural work is defined manually, by personal sensitivity or measurement to specific and static context. Parametric design needs to define performative goals, and the form is derived from this framework. In this way, if you adjust the goals, the form flows out of this change "for free". Sculptural design says the lines should intersect THERE. And the next point of the sculpture must similarly be pinpointed for that space/time instant regardless of how it was specified in the last instant. Parametric design says that the line should intersect at a defined distance from some contextually significant element. This relationship may then be applied as a RULE in all such recurring instances. Parametric geometry defines relationships rather than forms, to achieve the form in your head you need to understand it's derivation.

This is the difference between a playlist/sculptural and a Pandora/parametric approach. A playlist is direct, inflexible, and highly predictable after it has been made. Pandora is - or at least can be - exploratory, dynamic, and surprising after it has been set in motion.


  1. Thanks, man! That was great. Profound even. Your written contrast between sculptural design and paramentric design is something I am going to use in my teaching (with proper credit of course)...if you don't mind.

  2. Thanks, and no, I don't mind at all!

  3. Zach, great article! As a huge fan of both Revit and Pandora, I found your parallels to be really fitting.

    I've run into some of these pitfalls myself while building complex parametric families and when I stepped away for a minute and really thought about what I needed the family to do instead of how I thought I should build it, things got simpler and the family was much more powerful and parametric as a result.

    Just as in real families, the more 'hard and fast' rules your set, the more rebellion and tension you're going to have! If you establish parameters and guidance instead of a bunch of constraints, you'll probably have much more cooperation!

    Now if I could just keep the Beatles from showing up on most of my Pandora stations uninvited... No offense to the Beatles, but I don't care to hear Eleanor Rigby when I'm tuned in to MGMT.

    Patrick Villella
    Twitter: pvillella


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