A GDTF Workflow: How It Works and Why It Matters

 

By Richard Cadena

Ever since the General Device Type Format (GDTF) was developed by MA Lighting, Robe, and Vectorworks in 2019, I've been curious about where it would go and how it would help speed the deployment of a lighting design for programmers, electricians, and technicians. GDTF is a standard way to describe fixtures, including geometry, photometrics, and DMX mapping, so that CAD programs, visualizers, and lighting consoles from any manufacturer can all work with the files. In addition to the three founding companies, many other entertainment lighting manufacturers are embracing GDTF and its companion exchange format, My Virtual Rig or MVR. The prospect of standardizing a show file that works across several applications and manufacturers seems to be materializing.

But last year, when I was working as the head electrician on a large corporate event, I tried using a workflow that used GDTF and MVR to help streamline the process of patching fixtures. It didn't work. Because we had a show to do, I didn't have a lot of time to figure out why. Now that I have time, I decided to go back and see if I could get that old file to work.

Why GDTF?

A GDTF file has a lot of information about a fixture or device that we need to put a show together. It has the manufacturer and model, physical geometry (3D model of the fixture), available modes and their DMX footprints, control channels, gobo and color wheel data, and more. While GDTF standardizes the behavior and appearance of a fixture so it can be used across different platforms, its companion format, MVR (My Virtual Rig), bundles a scene, including fixture positions, patch data, and GDTF references, so that it can be used for different applications like a CAD program, visualizer, and lighting console. You can create a 3D model in Vectorworks, patch your fixtures, export it as an MVR file, then when you import it in the console or visualizer, the fixtures are positioned correctly, and they have the correct DMX assignments. It saves time by reducing duplication and it reduces errors for the same reason.

Setting Up Fixtures with GDTF Data in Vectorworks

The file I was using for the show was created in AutoCAD, then ported over to Vectorworks. The lighting designer, Rob Holland, laid out the plot and assigned the channel numbers. He then handed it off to me, and I circuited the fixtures, assigned DMX addresses, the mode, and fixture numbers. I wanted to port an MVR file from Vectorworks to a grandMA3 console to save time in the shop.

The key to success with exporting an MVR file from Vectorworks is to make sure each lighting device in the Vectorworks plot is associated with a GDTF profile. That's what was missing the first time I tried it. Vectorworks uses a few key fields behind the scenes to manage this link. A lighting device has a Light Info Record (the data record attached to lighting symbols), and within it, among others, there are fields for GDTF Type ID and GDTF Fixture Mode. The GDTF Type ID corresponds to a specific fixture type on the official GDTF Share website (www.gdtf-share.com), and the Fixture Mode field can designate the default mode if you want to pre-select a particular mode. When these fields are populated for a lighting symbol, Vectorworks can automatically fetch and attach the correct GDTF file.

As an example, suppose you have a Robe MegaPointe in your plot. You can edit the symbol's Light Info Record and manually enter the GDTF Type ID that matches the MegaPointe on GDTF-Share and perhaps set the Fixture Mode to “Mode 1 (39 ch)” if that's the mode you want to use. If you don't know the Type ID, you can use the “Open GDTF Share Connection” command (found under Spotlight > GDTF) to browse the GDTF Share library within Vectorworks. This opens an embedded browser where you can search for your fixture by manufacturer or model and log in to download the GDTF file directly into your project. Once it's downloaded, the GDTF profile becomes a resource in the Resource Manager, which is the central library where you can find, organize, and manage reusable content in your drawing.

You can also manually attach a GDTF profile to a lighting device in your drawing by selecting the device and choosing the GDTF fixture and mode from the Object Info Palette (OIP). Select the fixture's GDTF resource and mode in the GDTF fields, and check “Use GDTF Geometry” if you want Vectorworks to display the fixture's 3D model from the GDTF file. The DMX footprint (number of channels) will update automatically based on the chosen mode.

The Workflow

Rob, the LD, mentioned to me that some of the symbols in the lighting plot were older. He had done the original plot a few years prior and updated it every year using the old plot as a template. I used the Spotlight -> Lighting -> Replace Lighting Devices command to replace the original symbols, and I chose new symbols from the Vectorworks Resource Manager that already had a GDTF profile. Once all the symbols were replaced, I exported an MVR file.

I then switched over to the grandMA3 software and started a new show file. It was a simple matter to go into Settings -> Patch -> Import MVR to get the party started. The trickiest part in using grandMA3 OnPC is making sure the MVR file you want to import is in the proper directory, which, in my case, is in Users/rcadena/MALightingTechnology. (I'm on a Mac using Sequoia 15.3.1.) Then you have to find the User tab in the Import MVR window. When you click on Import, it shows a progress bar indicating how many MVR Import Scene Objects there are, how many have been sent, and how much data that is. When it finishes, the MVR Merge window opens, and it has an Import MVR button. After you click it, the window closes, and the Patch window opens. That's it.

The first time I did it, I thought it didn't work because the Patch window showed a long list of geometric objects, none of which had a fixture name, Fixture ID, or DMX address. So I thought it didn't quite work right. But when I exited and saved the patch, the entire model, fixtures and all, there they were in the grandMA 3D viewer. I could even select fixtures and turn them on in the integrated visualizer . It took me a while to figure out what was going on. I went back into the Patch window and eventually realized that there were so many objects that I had to scroll way down the patch to find the fixtures, which included the Fixture ID and DMX address.

Looking Ahead

In 2006, Remote Device Management (RDM) was launched, but it took at least 10 years before it caught on in the industry. I think the reason it finally took off is because City Theatrical launched the DMXcat, which was an affordable and practical solution for using RDM. In the case of GDTF, I knew very few people, if any, who have used it, and I have asked a lot of people.

Vectorworks Spotlight first implemented GDTF and MVR support in version 2019, and subsequent versions have expanded GDTF capabilities: Vectorworks 2021 (SP3) introduced a built-in GDTF Fixture Builder to edit or create .gdtf files within Vectorworks, Vectorworks 2024 added the ability to import 2D components from GDTF for hybrid symbols, and Vectorworks 2025 delivered the GDTF File Mapping feature with direct GDTF Share integration.

Now that it's practical and affordable, and I know it works, I think it's poised to become an integral part of the industry.