How to Build a VR DIT Cart

Me, operating our DIT cart on the set of a recent job we did at Light Sail VR

Those of us who have been on professional film productions anytime in the last two decades or so know the utter importance of having a qualified and talented DIT on set. DIT stands for “Digital Imaging Technician” and involves skills far more than simply copying and verifying media from digital cameras to hard drives. A really good DIT is able to work closely with the cinematographer and director to help inform creative decisions and help communicate to important stakeholders.

My expectations for a DIT have always been high. Having a strong post production background and invented many of the workflows I use on all of my 360 and 180 immersive video projects, I have built a skillset that proves extremely valuable to myself, but also to other creatives when we collaborate. I want to share my techniques and tools here, in hopes that it inspires others to jump in, learn, and improve upon what I’ve started.

A VR DIT needs to be able to accomplish the following tasks:

  • Organization of Media from many cards. This means having super fast storage and enough bandwidth to import data and back it up. Having several USB 3.0 interfaces along with several card readers is a good idea. Most traditional DITs roll in with one or two readers, but 360 cameras often capture media on six or eight. The Yi Halo uses a whopping 17 micro SD cards. In order to do the job on set and deliver a fast turnaround, you need a good system and you need to understand data rates, bandwidth of the peripheral bus, hard drive speeds, etc.
  • Rough stitching. Knowledge of PTGui and stitching software such as Mistika VR is essential. You should be able to take the images from the card and generate a rough stitch for review by the creative team. And you should be able to do this as quick as possible. Nobody wants to wait around for hours while you struggle with the technology.
  • Color management. This is less important with some cameras, but with many high end productions now filming with professional level cameras, understanding how LUTs work and how to interpret a raw image is very important. Especially for any stakeholders, they might need to see a “rough grade” so they feel confident in the image that is being captured.
  • Live preview. Many 360 cameras do not offer a great way to see what is actually being captured. While I understand this is traditionally the job of a VTR technician, on the small crews of a a 360 production, my expectation is that the DIT also understands how to help the team review what is being captured. The DIT should be able to unwrap the fisheye images from the cameras into equirectangular space and rectilinear space for review at various FOV sizes, including headset preview if needed.

The Light Sail VR DIT Cart

Here is what I have built and why I chose each component.

Filmtools Vertical Cart
I like this cart because it’s compact and tall. I’ve added a few shelves onto mine as well as a triple baby pin adapter to hang my monitors.

Atomos Sumo 19" Monitor
This monitor acts as a confidence monitor, but also has the ability to record. Recording the unwrapped image is a really great way to offer quick playback on set for stakeholders to confirm they are ready to move onto the next setup.

APC 1500x UPS Battery Backup
Having the whole system running on a battery backup is smart because it allows me to unplug my cart and push it to the next setup or location without having to shut everything down and boot back up again. Mine gives me about 12 minutes of run time.

TP-Link AC750 WiFi Adapter
This tiny portable wi-fi hotspot allows me to create my own ac-hoc 5Ghz network so that I can connect my Oculus Quest 2 in AirLink mode wirelessly.

Custom Built PC
You can use whatever you like here, but I’d recommend an NVIDIA graphics card that’s good enough to stitch at the razer size you require, as well as a good CPU and plenty of RAM. You’ll also need a Blackmagic Decklink 8K Pro card to handle video input/output from professional camera rigs. Personally, I roll with a RTX Titan, AMD 1950x Threadripper, 96GB RAM, and an extra USB 3.0 PCI card. The case I use also has handles, making it pretty easy to pick up and move.

Asus ProArt 24" Monitor
This is just a standard HD computer monitor, but with pretty good color. It’s calibrated with my iDisplayPro. I am looking to potentially swap this out with a touchscreen monitor.

Oculus Quest 2
The Oculus Quest 2 is my favorite headset for comfort, price, and quality. I have it linked up via AirLink so that I can have a truly wireless experience. By utilizing a custom app I built to push NDI signals to the headset, I am able to view stuff on set, in headset. This is incredibly valuable to be able to make creative decisions regarding camera height, proximity, and stereo convergence.

Needed Software

There are a few pieces of software I highly recommend adding as part of your kit if you decide to become a VR DIT.

Hedge
Hedge is fantastic for backing up and transferring footage from cards. It’s fast, very customizable, and you can even check the status of transfers from your phone. Very cool.

PTGui
The classic stitching software. This is very useful for creating custom stitch templates for Mistika VR (to deal with custom camera geometry or difficult scenes). I use an older version (version 10) which is more compatible with some of the tools Andrew Hazelden have created.

Mistika VR
It’s important to have a tool that’s able to handle any camera input and quickly stitch together an image for viewing. Mistika VR is fast and flexible. Being able to also spot potential stitching issues on set can also help inform the team of any plates they may want to get as well as help get ahead of post production headaches before leaving the set.

DaVinci Resolve Studio
Since we’ve built our setup with a Blackmagic 12K camera, DaVinci Resolve Studio (and Fusion, which comes bundled with) are pretty good tools to have. Especially when paired with Andrew Hazelden’s KartaVR, which is a free set of tools designed to help folks work in spherical formats inside Fusion. KartaVR has an amazing tool that will generate STMaps from PTGui stitch files so you can use them in applications such as Touch Designer for realtime stitching.

Touch Designer
This is the application that creates all the real-time magic that allows us to unwrap the image and broadcast it to other sources. I’ve only scratched the surface of this amazing tool, but it’s worth it.

Have questions? Building your own cart? Want to work as a DIT in VR? Get in touch and let’s talk. matt@lightsailvr.com