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How to begin experiencing GDL
There are two methods for creating new library parts:
Create a 3D model from
slabs, walls and other elements / objects, especially using the objects
that can be found in the Primitives folder in the ArchiCAD
Library. Make sure that one corner of the resulting 3D model
is at the absolute (x=0,y=0) origin, because this will be the local origin
of that library part. If not, use the Drag command to move your model to
the origin. Activate the 3D Window and set the viewpoint the top view.
Then save it as an ArchiCAD Object File (.GSM file).
You can then choose between Editable GDL Script and Non-editable binary 3D
data. Generally select the Editable GDL Script option to be able to
modify the 3D script and to add new parameters to the parameter list
of the resulting object. If you open such a library part, you will find 3 parameters (A,B,ZZYZX) in the parameter
list, an editable 3D script generated by ArchiCAD and a 2D symbol that is
a stretchable, vectorial 2D representation of the object. The 3D
script contains 3 major parts:
The first contains the comments (In GDL, "!" means that the next characters in that row should not be
interpreted by ArchiCAD), the second contains the global variables (see
the Appendix in the ArchiCAD GDL Reference Manual for a List of Global Variables) and only the short
3rd part is which
creates the 3D representation of the object.
(GDL=Geometric
Description Language) Using the GDL Reference Manual, you select the
appropriate 2D/3D GDL commands and create your scripts. GDL is close
to BASIC or PASCAL programming languages, but generally no
programming skills are required to begin experimenting GDL. There are
different command families, such as coordinate transformation
commands (such as add2/addx), 2D/3D shape commands, mathematical and flow
control commands and other non-geometric scripts.
The same library part created in GDL has a shorter 3D script and the 2D
symbol can be replaced by a simple 2D GDL command in the 2D script.
Pros/Cons:
When you create library parts from drawn elements, you can create
objects without writing GDL scripts. However, the resulting objects will be less
parametric: you can control the length/width/height parameters only. When
you create GDL objects with your own scripts, you can use many parameters
of different type and you can even define value lists. You will also be
able to modify any component of your object or add a new parameter to it very easily.
Page last updated: Thursday, September 16, 2004
