Computer Aided Design using FLOSS: An Interview with Franz Reiter, lead developer of gCAD3D

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Today we share with you an interview with gCAD3D lead developer Franz Reiter. gCAD3D is an interactive Computer Aided Design tool that can be used by engineers for prototyping models in three dimensions. Enjoy the interview!

F4S: Hi Franz. Please, give us a brief introduction about yourself.

I started in 1973 as a designer for videorecorders at Phillips. I started programming small applications and in 1981 I began as an application-programmer for Tektronix grafic-terminals at Rohde & Schwarz-Textronix.

Since 1984 I produced technical software and add-on-programs for CAD-systems (Catia), for the companies MatraDatavision, IBM, MAN-Austria, AIRBUS-Hamburg and others. Later I did many postprocessors and some NC-modules (eg CATWIRE).

In the last years I have also worked for a company that produces software for road-construction. (Autocad-Civil Add-Ons).

F4S: What is gCAD3D?

gCAD3D is a CAD-CAM-software. Unlike other CAD-software its native format is ascii (text, like dxf or iges, but parametric).

It is an interactive CAD and a development-system for most cad-related applications. Import-/exportformats are Step, Iges, VRML, DXF, SVG. gCAD3D may be used for any purposes free of costs.

The software has 3 different options for automatization: scripts, catalogparts and plugins.

  • Scripts and catalogparts are parametric also, but interpreted (slower).
  • Plugins (shared overlay libraries) can get unlinked, recompiled and relinked without restarting the core-software.
  • Plugins support application-objects and application-data.


F4S: Why and when did gCAD3D come to be?

The reason for the development was to have a tool for rapid cad-software-prototyping.

The first version came up in 1995 and was named “xcad” and had a Motif-Interface. Since 1998 GTK was used to build the user-interface and the name was changed to “gCAD3D”.

Gcad then did already exist (2D, “Gtk-Cad”, the author was Inigo Serna Robledo).

F4S: In which language(s) and platform(s) is the project developed?

gCAD3D is available for Microsoft Windows and Linux, the primary development-platform is Linux. The language used is C. Reasons for using C are: high compatibility for a VERY long period, high compatibility on all platforms, high processing-speed.

F4S: Does gCAD3D have sponsors?

gCAD3D does not have direct sponsors.

Many modules of the software come from commercial projects. However, the core-libraries of gCAD3D are also used for commercial projects.

For usability reasons the software modules are strictly separated.

F4S: How many users you estimate gCAD3D have? has around 300000 visitors per month, and the software is hosted on software.informer, softonic and others also.

The use of the software including all add-ons is absolutely free, we do not have any advertising or registration on our server, so the number of users is unknown.

F4S: How many team members does the project have?

We are 3 core-programmers.

F4S: In what areas of gCAD3D development do you currently need help?

We could need help for translations, testing, documentation, mathematic
analysis, programming, internet activities …

F4S: How can people get involved with the project?

Install and test the software and tell us what you think.

F4S: What features are in the roadmap?

The next version will have improved usability (interactive-help), an improved installation-process for Linux (.deb – package) and many bugfixes.

The next goals are offset-surfaces, rounding of surfaces and kinematics.

F4S: Why do you consider free/libre open source software important for
the advancement of your field?

CAD will be one of the most important applications in the future, since it is the key to many other applications – manufacturing, engineering, science.

And Cad-systems get more complicated every year – and more expensive.

So, how can an open-source CAD-system be realized ?

I think, it is not possible for a single person to create a cad-software. Cad-systems need many modules with thousends of functions. There exist many useful free software packages, but they do not fit together.

To be able to start a community-project a lot of definitions would have to be done:

  • the functionality of the different modules must be defined
  • some formats must be documented

Some words about the formats. CAD-programs need some different formats for their objects:

  • the exchange format.
  • the native format.
  • the internal binary format.
  • the internal display format.

Exchange formats are dxf, Iges, Step. The native format is used for the internal storage – fully parametric. Should be easy to read and understand. It should be well documented, and: it should be possible to extend it.

The internal binary format keeps the active state of an object, the evaluation of the parameters is already done. This format must be known if you want to provide add-on-software.

The internal display format is used to simplify the object for the display-functions. This format is also used for the Virtual Reality-exporters and other mockup-functions.

This may give an idea of the complexity of a cad-system. This first step – setting up functionality and formats – is the hardest.

There have been some attemps in 1990 – see

If you know of initatives like this, please let me know.

With gCAD3D we try to find the best solution for a open cad-architecture. Nevertheless I hope, that one day I can contribute to a community-driven open-source cad-software.

F4S: Where people can contact you and learn more about gCAD3D?

The gCAD3D-website is
Contact us at

Mit freundlichen Gruessen

Franz Reiter

F4S: Thank you for your time Franz.

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