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Easier Way to Create GDL Objects

Not applicable
I am fairly new to AC and am trying to get a handle on creating objects similar to creating families in Revit. I opted for AC instead of Revit for multiple reasons (and I don't intend this to be a topic about that), but I need a fast way to grasp creating editable objects in 3d like tapered beams, open web trusses, etc. For example, I have a current issue trying to create an open web truss that is tapered. Using the truss maker is fine, but once an object is created (truss maker or not), I have to somehow edit the GDL to add hotspots to it (because the corners don't all line up with the eight default corners in 3d. Why is this so difficult? Is there a better way? Surely, I am missing it. I also totally accept that I should probably dive into the GDL scripting more. However, as a new user, and wanting to develop projects faster, the last thing I want to do is learn a (new) coding language. I appreciate all the documentation online about GDL and I accept all the benefits it provides, at least on the surface (smaller file sizes, etc). However, for people trying to get going with AC and make parametric objects quickly, it's a huge hurdle, at least for myself. Please advise and feel free to tell me I am totally missing something.

As a brief post script, the tertiary issue with this is that so many manufacturers make Revit files for their products, but AC has been left out from the vast majority of US products. Is this an issue for anyone else? How do we bring these objects into AC and make them beneficial? Is it even necessary? I have a Revit importer for such objects in AC now and they become the standard simple objects without any parametric settings. Ugh.

Barry Kelly
I am sorry to say that if you want to make parametric objects, then you will really have to learn GDL.

Saving as an object or converting Revit objects is only going to give you a static object as you have discovered.

There is a 'Library Part Maker' add-on available to some subscription users in certain locations (UK for example but I believe some other locations as well).
But even this only creates a static object that has various options for showing different levels of detail depending on scale.
I don't really know that much about it as I don't use it.

GDL really is your best option.


One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10

And GDL allows making far more parametric objects and less computer power consuming than the "R" families 😜
but of course it needs scripting not just modelling.


Not applicable
Thanks for the replies. Are there recommendations on the best places to start with GDL?

There is the "GDL Cookbook by David Nicholson" which while a bit out of date, is still a pretty good starting point. There are also a couple of tutorials by GS that I found useful as they are for basic parametric objects and include a finished version that is easy to examine.

AC22-23 AUS 7000
Self-taught, bend it till it breaks.

Win10 | E5620 x 2 | 24GB | K2200 RIP PSU
Win10 | R5 2600 | 16GB | GTX1660

Barry Kelly
I found the best place to start was the GDL Cookbook by David Nicholson-Cole.
It is quite old now and hasn't been updated, but the basics are all still there.
I still use it nearly 20 years on.
It is not available as a book anymore but can now be downloaded for free ...

I believe there is a slightly update version 4.0 of the book as well somewhere.

Follow the 'Useful Links' at the top of this page to the GDL Center.
There is some good info there as well.

There are others sources a s well of course.
Search +learn +GDL in the forum here and see what else you find.


One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10

If you want a full parametric object, you probably need GDL. But it's not an all or nothing proposition. You often can take a "dumb" object and add a parameter or two and make them far more useful. Gary Lawes did a couple of lessons on hacking existing GDL objects for Eric Bobrow's "Masters of ArchiCAD" series that Eric could probably sell you very cheaply. See also: And frankly, you don't really NEED to script everything. For example: You also can now convert objects to morphs and have quite a bit of control over materials and sizes. Somehow, I've managed to scrape by for the past twenty years without becoming a GDL guru.
Richard Morrison, Architect-Interior Designer
AC25 (since AC6.0), Win10

Not applicable
Thanks for the help. Does anyone know if AC plans to update or progress any of the GDL workflow in the coming years? It looks like it's been the same for a while with only minor changes with new commands added. It would be good to know if AC plans to roll out updates for GDL so we aren't referencing a book from 15+ years ago. Also, when searching for help videos, only very old references come up. I would say that's a general gripe I have with getting familiar with pieces of AC. The reference materials online, at least as far as videos are concerned, other programs like Revit tend to have a constant flow of updated videos and instructions being posted so it feels like AC is at times ignoring that aspect. On the surface it seems like the program is lacking relevant info, IMHO.

Eduardo Rolon
You can start here

Which has its own separate forum and is updated more frecuently.
eduardo rolón AIA NCARB
Another of the forum moderators.
Macbook Pro M1 Max 64GB ram
OS X 10.XX latest
AC25 US/INT -> AC08

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