Geometric Description Language
Encyclopedia
In computer-aided design
, Geometric Description Language (GDL) is the programming language
of ArchiCAD library part
s. GSM is the file format
of these CAD objects.
, but unlike blocks, these are parametric, and the 2D and 3D features are connected, so in any view one can get the correct visualization (for example a side view on the section, top view on plan, and perspective in the 3D view). GDL scripts define an ArchiCAD library part in its main roles, these are 3D model, 3D model projected to section/elevation or to 2D plan, 2D plan view, user interface
display and behaviour and listing quantities.
All versions of the ArchiCAD
contain their own default libraries, also objects like furniture, windows, doors, trees, people, cars, construction elements, etc.
There are several commercial websites for selling high-detailed intelligent parametric objects, which are perhaps better and more variable than the default libraries, for example there are a lot of environmental objects like plants, people or garden elements, which are not included in the original software.
-like. It has the same control flow statements and variable logic.
In 2D and 3D in GDL, all the model elements are linked to a local right-handed coordinate system
. For placing an element in the desired position, you have to move the coordinate system to the desired position (and orientation), then generate the element itself. Every movement, rotation or stretching of the coordinate system is called a transformation
. Transformations are stored in a stack
, which can extended by further transformations and can be cut by deleting one or more transformations from the top of it.
GDL is backward compatible, which means that an ArchiCAD library part
will be readable with every subsequent ArchiCAD program, but with none of the earlier versions.
For detailed technical specification consult the GDL Reference Manual of the latest ArchiCAD release.
Computer-aided design
Computer-aided design , also known as computer-aided design and drafting , is the use of computer technology for the process of design and design-documentation. Computer Aided Drafting describes the process of drafting with a computer...
, Geometric Description Language (GDL) is the programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
of ArchiCAD library part
ArchiCAD library part
ArchiCAD library part is the basic item through which the CAD software ArchiCAD handles external dynamic content elements which are grouped into libraries...
s. GSM is the file format
File format
A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...
of these CAD objects.
Area of usage
These objects are similar to blocks in AutoCADAutoCAD
AutoCAD is a software application for computer-aided design and drafting in both 2D and 3D. It is developed and sold by Autodesk, Inc. First released in December 1982, AutoCAD was one of the first CAD programs to run on personal computers, notably the IBM PC...
, but unlike blocks, these are parametric, and the 2D and 3D features are connected, so in any view one can get the correct visualization (for example a side view on the section, top view on plan, and perspective in the 3D view). GDL scripts define an ArchiCAD library part in its main roles, these are 3D model, 3D model projected to section/elevation or to 2D plan, 2D plan view, user interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
display and behaviour and listing quantities.
All versions of the ArchiCAD
ArchiCAD
ArchiCAD is an architectural BIM CAD software for Macintosh and Windows developed by the Hungarian company Graphisoft. ArchiCAD offers specialized solutions for handling all common aspects of aesthetics and engineering during the whole design process of the built environment — buildings, interiors,...
contain their own default libraries, also objects like furniture, windows, doors, trees, people, cars, construction elements, etc.
There are several commercial websites for selling high-detailed intelligent parametric objects, which are perhaps better and more variable than the default libraries, for example there are a lot of environmental objects like plants, people or garden elements, which are not included in the original software.
Licensing
GDL is a free technology (although ArchiCAD itself is a commercial software), it is allowed and possible to develop GDL based object libraries using free tools like Graphisoft LP_XMLConverter and Graphisoft GDL Web Plug-In.Technical information
The GDL programming language is fundamentally BASICBASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....
-like. It has the same control flow statements and variable logic.
In 2D and 3D in GDL, all the model elements are linked to a local right-handed coordinate system
Coordinate system
In geometry, a coordinate system is a system which uses one or more numbers, or coordinates, to uniquely determine the position of a point or other geometric element. The order of the coordinates is significant and they are sometimes identified by their position in an ordered tuple and sometimes by...
. For placing an element in the desired position, you have to move the coordinate system to the desired position (and orientation), then generate the element itself. Every movement, rotation or stretching of the coordinate system is called a transformation
Transformation (mathematics)
In mathematics, a transformation could be any function mapping a set X on to another set or on to itself. However, often the set X has some additional algebraic or geometric structure and the term "transformation" refers to a function from X to itself that preserves this structure.Examples include...
. Transformations are stored in a stack
Stack (data structure)
In computer science, a stack is a last in, first out abstract data type and linear data structure. A stack can have any abstract data type as an element, but is characterized by only three fundamental operations: push, pop and stack top. The push operation adds a new item to the top of the stack,...
, which can extended by further transformations and can be cut by deleting one or more transformations from the top of it.
GDL is backward compatible, which means that an ArchiCAD library part
ArchiCAD library part
ArchiCAD library part is the basic item through which the CAD software ArchiCAD handles external dynamic content elements which are grouped into libraries...
will be readable with every subsequent ArchiCAD program, but with none of the earlier versions.
For detailed technical specification consult the GDL Reference Manual of the latest ArchiCAD release.