Technology: What in the Heck is GDTF?

by Michael Eddy
General Device Type Format (GDTF) is a new open data standard for linking luminaires, consoles, CAD, and previsualization software.

You may have heard about a new open data format to help streamline the process of linking a fixture profile from CAD through previsualization and on to a console. This new development, named General Device Type Format (GDTF) was created to change the way lighting designers and programmers in the entertainment design and production industry work. In an effort to make lighting fixtures, visualizers, and consoles work together in a more seamless way, three manufacturers—MA Lighting, Robe, and Vectorworks—jointly developed this open standard format. GDTF is a way to try and create a unified definition for the exchange of device data.
Currently, most device manufacturers use a proprietary way to define their luminaires. This lack of a standard or unified definition requires lighting console manufacturers to support and maintain a complex web of file formats. Moreover, it makes it virtually impossible for designers to import CAD files into consoles and makes it very difficult to link CAD software to previsualization software.

With GDTF, luminaire manufacturers now have an open and universal data exchange format that can be read by any console manufacturer and be included in any CAD or previsualization software. No longer will custom, one-off interpretations of DMX values and conversions for specific control data be needed. The format is human-readable, royalty-free, and designed to be easy to implement and maintain.

What Exactly is GDTF?
Will Murphy, director of software support and development with A.C.T Lighting, Inc., helps clarify and better explain GDTF. “Since the announcement of GDTF, just prior to PL+S, I have already come across much confusion among people about GDTF,” says Murphy. “As you know there are manufacturers of fixtures, lasers, pyro, water effects, and more and all these products have to be controlled, visualized, or both. Naturally the creators of these products want the users to have the best experience, whether it be from a drafting, control, or visualization standpoint.”
“In the past, to achieve this process, the manufacturer created a PDF manual that goes to all the makers of controllers, visualizers, drafting software, and more. Someone within these receiving companies manually converts the data to their system and may not have received all the info from the manufacturer of the product. Thus, the long-term process begins of trying to get the needed info from the manufacturer while at the same time the manufacturer may create revisions and changes that get pushed out to everybody in a new PDF.”

At this point you’re probably thinking that Murphy is talking about just DMX channels. He is talking about way more than just DMX. All these products have physical dimensions, might output a specific range of colors, might have built-in effects, and more. Murphy asks, “Wouldn’t it be great if the makers of these products had a standardized container file where they could input all the information their hearts desire and then controllers, visualizers, and drafting software could just read this information and adapt it to their products?" This my friends is GDTF. It’s just a file. It’s kind of like a .txt file or .xml file, but it’s a .gdtf file.

It’s a File Format, Not a Protocol
When you go to the GDTF website, you will see the phrase ‘GDTF Protocol’. To be clear, GDTF is not a network protocol in the way we use the term protocol in our industry. It’s not a replacement for DMX. Instead they chose the word protocol to mean: ‘the official procedure or system of rules governing affairs.’ “To speak about GDTF in regard to moving lights, GDTF is a file that contains as much or as little info about a fixture as the manufacturers choose to put in it,” explains Murphy. “If a fixture manufacturer puts a 2D symbol in the GDTF file, then drafting software can use this symbol. If a fixture manufacturer puts three-dimensional info about a fixture’s physical size in the GDTF file, then visualizers or CAD software may use this to represent the fixture more realistically. If a fixture manufacturer puts the true color space details in the fixture per what colors it can output, then a controller is able to more easily control that fixture and match the color output with other fixtures in the rig.”

“I hope you are getting the idea now how great GDTF is in moving our whole industry forward and improving everything about what our friends and colleagues do on a daily basis,” continues Murphy. “Ultimately, the more people that embrace GDTF and the more info that goes in to the GDTF file, the better experience users will have. Speaking about DMX alone, the GDTF file will contain channel arrangement for all modes and all revisions.”
GDTF is open source and royalty free. There is no real extra benefit coming to MA Lighting, Robe, or Vectorworks, other than they are slightly more prepared for it in the software they have. “However, if all companies embrace this through an industry-wide push, then in less than one year our industry will easily be sharing the data we otherwise could get through a much longer process of back-and-forth emails with many colleagues,” notes Murphy.

Exchanging Information
As a part of the GDTF development, a tool has been created called MVR format (My Virtual Rig). “MVR is a data exchange protocol to share data between a lighting console, a visualizer, a CAD program, or similar tools,” explains Murphy. “Naturally it has provisions to share GDTF file data plus more. Data that could be shared with MVR might be channel numbers, DMX addresses, xyz position information, and xyz rotation information. MVR is how we might one day see a bi-directional sync between Vectorworks and grandMA3, or grandMA3 and Lightwright, or many other industry tools.” Currently, only Vectorworks and MA Lighting support MVR files.
The plan is for GDTF to continue to be developed and the format will be updated periodically as technology evolves and more manufacturers adopt the format. GDTF was developed to be both extensible and backward compatible so it realistically has the potential to be a powerful answer to a frustrating problem. Murphy concludes, “GDTF is super clever and will change how everyone works in the industry—if everyone will choose to embrace it.”

It will be interesting to see how the industry embraces GDTF, so far it has been positively received. Though at the moment only MA Lighting, Robe, and Vectorworks support GDTF, several manufacturers are supportive of the idea. Currently, ADB Stagelight, Atlabase, Avolites, Ayrton, Carallon, ChamSys, Claypaky, DTS, ETC, GLP, Golden Sea, Green Hippo, JB Lighting, Martin by Harman, Robert Juliat, SGM and Zero 88 are on board with the file format as noted on the GDTF website. For designers, programmers and technicians, streamlining the process would be greatly appreciated, giving them more time to create bigger and better designs. We will keep checking on the adoption process in the industry moving forward and it should be telling how adoption is going at the upcoming tradeshows in the fall.

Frequently Asked Questions
The support site for GDTF (www.gdtf-share.com) has a number of FAQs about the concept and lots of good information. If you are interested in learning more about GDTF, I suggest checking the site out. There’s also a companion Wiki with further information as well, which you can reach here: http://gdtf-share.com/wiki/Main_Page.

A few of the most telling FAQs include:
Q: Is GDTF reviewed by the ESTA Technical Standards Program and approved as an ANSI standard?
No. In the future, GDTF may be submitted for review to the ESTA Technical Standards Program, but at this time it is simply an open standards-based format controlled by the founding member companies.

Q: How do I know if a product I use supports GDTF?
Look for the GDTF file icon, consult this website for a list of companies that support the file format, or contact the manufacturer directly. If a manufacturer does not currently support the file format and you’d like to participate, contact the GDTF development group at the GDTF Wiki.

Q: If a manufacturer hasn’t provided GDTF data for fixtures, can I manually create GDTF files for these fixtures?
You can create GDTF files by following the specifications outlined on GDTF Wiki, or you can use the MA Fixture Builder to create a GDTF file.

Q: Do symbol libraries in Vectorworks Spotlight or Vision support GDTF?
When the files are available, Vectorworks will automatically associate both a GDTF file and a Vision .lit file with each symbol. You can manually select either file in Vectorworks to choose a different fixture or mode. Vision does not currently support GDTF files. Vision support for GDTF files will be added in a future version.

Q: Where can I find more information on the technical specificationsof GDTF?
Technical information, tutorial and File descriptions can be found at GDTF Wiki (http://gdtf-share.com/wiki/Main_Page)