Guest Blogger Djordje Grujic: Untangling the Arcane Secrets of GDL
“The sea is dangerous and its storms terrible, but these obstacles have never been sufficient reason to remain ashore… Unlike the mediocre, intrepid spirits seek victory over those things that seem impossible… it is with an iron will that they embark on the most daring of all endeavours… to meet the shadowy future without fear and conquer the unknown.” Ferdinand Magellan, Explorer (c.1520)
Every time I think of GDL, the first person that comes to mind is David Nicholson Cole, better known in the ArchiCAD Virtual Universe as DNC. And every time I stumble upon his GDL Cookbook, or his OMWAC (Object Making With ArchiCAD) book, I remember the brilliance of British eccentricity, Douglas Adams, Dirk Gently, and that the answer is 42.
Of all the things insanely great (you know whose quote this is, right?), GDL is the most arcane I have ever met. Born of the Hungarian mathematical genes in order to model the pipeworks of a power plant some 30 years ago, it grew to become something many of us hold dear—ArchiCAD. Yep, that’s the core of the modeling engine of the first and only surviving architectural BIM software from the early 1980s. As it is the very essence and the very core, it is somewhat understandable that for decades GDL has been an arcane art and an extremely well kept secret, often at its own expense. There was a GDL manual, most useful for the person(s) that wrote it, and considered among the users as the most refined type of cruel and unusual punishment there is—unless you were a mathematician, programmer, Hungarian, or preferably all three.
And then … some time in the 1990s, the students at a course at the University of Nottingham asked their tutor a few questions too many.
ArchiCAD was in its 5.0/5.1 version (5.1 meant Teamwork), and the tutor—none other then David Nicholson Cole—sacrificed his weekend to learn GDL and answer his students’ questions. For those that arrived on this planet since then and don’t remember computers without a mouse: typing in a program from a magazine, or writing your own, never mind loading it from a cassette tape, was still a living memory. Anyway, after managing to get through the GDL manual in a weekend, despite not being a mathematician, programmer, or Hungarian, but an architect (and that is infinitely worse, trust me, I am one!), David Nicholson Cole understood the issue: STRUCTURE!
The key to good GDLing is structured programming. Each piece of the object should have its start, middle, and end, and the spatial orientation is of utmost importance. David Nicholson Cole kept this in mind when he wrote the definitive guide to learning GDL. The lessons in the GDL Cookbook take you through the coding for individual objects, from a simple chair to tower cranes, with stretchy, transformable, scale sensitive and other magical objects thrown in. And yes—and after finishing the GDL Cookbook, you COULD make those objects that you have always wanted, and that you once imported via DWG or 3ds format.
I got the first GDL Cookbook in 1998, just about the time that ArchiCAD 6.0 was about to be published. I did go through it, but without any real reason or need for knowing it; I kept it as an academic interest. Then, early 1999 brought me to the Arabian Peninsula, in the role of the regional Graphisoft distributor’s Technical Services Manager. I was responsible for technical support, presentations, and assistance to the clients—and those services included GDL scripting! The biggest client in Dubai already had some VERY interesting questions, and some of their staff REALLY wanted to learn GDL. So … after a couple of emails, David Nicholson Cole agreed to visit us in the depths of the summer, and to do a GDL course with the GDL Cookbook included!
That week with David Nicholson Cole, and the opening of the eyes of the ArchiCAD users was something to behold. I did not attend the course, but just talking to David about an Object or two that we worked on for our clients made me revisit the GDL Cookbook pages again and again… my personal record was scripting the whole Managing Director’s office in one afternoon, complete with curvy desks, fluffy cushions and deep sofas. I also learned what ZZYZX is and why is it called ZZYZX.
And here is the truth: you can do GDL, if you are disciplined, precise and understand space.
In 2000, Graphisoft finally commissioned David Nicholson Cole to write Object Making With ArchiCAD (OMWAC), the book that since has been mostly incorporated in the ever growing ArchiCAD documentation. It was revised in 2004, to follow the developments in GDL. We are now a good 15 years from the original GDL Cookbook, and 13 since the first OMWAC. Both ArchiCAD and GDL have changed, as one might expect. But the value of both these tomes has not diminished.
The power of GDL was almost forgotten, and it has been—and is—the secret weapon of many an ArchiCAD Jedi, of which I could name a few, like Frank Beister, James Murray, Jeroen de Bruin or the ArchiRadar and manuBIM teams. Forgive me, the rest of you. For your understanding of the dark arcane core of the machine, the heart of the system, you should know how to cook the soup of the essence.
And there is only one GDL Cookbook. Thank you, David.
Jared’s Note: If you don’t know who Djordje Grujic is and why I’m honored to have him write a guest post for Shoegnome, click here. As part of the guest blogger process, I do all the editing and formatting. So before I hit the publish button, I’ve already read this post a dozen times. And I’m inspired to download the GDL Cookbook to my iPad and finally take the plunge. Who’s with me. Who’s ready to face their fears and start programming. I’m also going to go e-mail David Nicholson Cole and see if I can get him to add some thoughts to the blog. You might want to follow Shoegnome on Facebook and Twitter so that you don’t miss what he might have to say. And while you’re at it, the RSS feed is a great way to never miss anything either.