topic Re: GDL Pgon code issue in GDL

GDL Pgon code issue

RhinoX — Sat, 06 Sep 2025 12:23:14 GMT

Hi everyone, I’m still learning GDL and wrote a simple script to create two triangular polygons using the pgon command. For some reason, it keeps throwing an error and I can’t figure out why. Any help would be much appreciated. Thanks!

vert 0.00, 0.00, 0.00 ! 01 vert 1.00, 0.00, 0.00 ! 02 vert 1.00, 1.00, 0.00 ! 03 vert 0.00, 1.00, 0.00 ! 04 edge 1, 2, 1, 0, 0 ! 01 edge 2, 3, 1, 0, 0 ! 02 edge 3, 1, 1, 2, 0 ! 03 edge 3, 4, 1, 0, 0 ! 04 edge 4, 1, 1, 0, 0 ! 05 vect 0, 0, 1 vect 0, 0, 1 pgon 3, 1, 0, 1, 2, 3 pgon 3, 2, 0, 4, 5, -3

Operating system used: Mac Intel-based

Re: GDL Pgon code issue

Lingwisyer — Thu, 04 Sep 2025 01:53:19 GMT

I have not tried using pgons, but does it work without the the vert 4 points?

Re: GDL Pgon code issue

RhinoX — Thu, 04 Sep 2025 14:49:21 GMT

No, it’s not possible. The points must be defined first before the edges can be determined.

Re: GDL Pgon code issue

Lingwisyer — Fri, 05 Sep 2025 01:28:54 GMT

I mean if you defined a single triangle rather than two with a common edge.

Re: GDL Pgon code issue

MF BIM — Mon, 08 Sep 2025 09:34:19 GMT

Hi @RhinoX ,

It seems that the issue is coming from the definition of pgon1 (the 3rd argument) in edge 04 (line 31)

I'm not familiar with primitive elements but from my understanding, arguments pgon1 and pgon2 are the indices of the polygons they refer to. Edges 04 and 05 are edges of the second polygon so pgon1 should be 2 I think.

It you do this, does it work ?

edge 3, 4, 2, 0, 0 ! 04 edge 4, 1, 2, 0, 0 ! 05

Re: GDL Pgon code issue

RhinoX — Thu, 11 Sep 2025 23:28:20 GMT

Thanks, will try your way. Actually, I have just started learning GDL, but it feels like getting lost in a forest of commands and syntax. For example, when creating a terrain mesh, there are too many similar commands like Mesh, Pgon, Mass, Coons… I’m not sure which ones people usually use. Some seem rarely used, since there are very few tutorials about them. I think Graphisoft should remove some of the less commonly used commands so that beginners don’t get overwhelmed.

Re: GDL Pgon code issue

Lingwisyer — Fri, 12 Sep 2025 01:53:01 GMT

The Primitives command set you are tinkering around with is what the automatically generated scripts use as it is just constructing triangles which while mathamatically very simple, are not very intuitive... I have not seen MASS or COONS used before, though coons seems like a more primitive version of RULEDSHELL... I feel like if you are going beyond Basic Shapes and Planar Shapes, you are going beyond a beginner level. A bit like the level of understanding between Python and C++.

If you are just starting out, find yourself a copy of the GDL Cookbook, though old and a bit out dated, it is still a great learning guide.

Ling.

Re: GDL Pgon code issue

RhinoX — Fri, 12 Sep 2025 15:53:40 GMT

Thanks a lot! I actually started with the Cookbook – it’s a fantastic resource – but it does feel quite old. I’m not sure if Graphisoft has introduced any smarter commands since then to replace the older ones. Right now I’m mainly trying to wrap my head around how Mesh works, and whether it’s possible to generate meshes through GDL using Grasshopper.

Re: GDL Pgon code issue

Lingwisyer — Sat, 13 Sep 2025 19:00:19 GMT

Fair enough, I should have known this query would have been somehow related to your other ones.

Regarding development of the language, I do not think there have been any modelling changes since I first played around with it during AC19... or at least any that would impact general use or process...

Ling.

Re: GDL Pgon code issue

rudl — Tue, 07 Oct 2025 13:00:10 GMT

base ! -> always add base vert 0.00, 0.00, 0.00 ! 01 vert 1.00, 0.00, 0.00 ! 02 vert 1.00, 1.00, 0.00 ! 03 vert 0.00, 1.00, 0.00 ! 04 edge 1, 2, 1, 0, 0 ! 01 edge 2, 3, 1, 0, 0 ! 02 edge 3, 1, 1, 2, 0 ! 03 edge 3, 4, 2, 0, 0 ! 04 ! -> pgon2 edge 4, 1, 2, 0, 0 ! 05 ! -> pgon2 vect 0, 0, 1 vect 0, 0, 1 pgon 3, 1, -1, 1, 2, 3 ! -> Status either specified > 0 or calculated < 0 but never just 0 pgon 3, 2, -1, 4, 5, -3 ! -> Status either specified > 0 or calculated < 0 but never just 0 body 1 ! always add body

should work hth