How To Use Composure For Real-Time Keying In The Unreal Engine | ActionVFX

How To Use Composure For Real-Time Keying In The Unreal Engine

How To Use Composure For Real-Time Keying In The Unreal Engine

As the industry continuously evolves, the real-time keying skill set will be highly sought after!

The Unreal Engine has enabled so many exciting advances in the world of VFX, and knowing how to place actors in a virtual space in real-time is going to become an increasingly valuable skill as the industry evolves.

An LED wall with synchronized on-set lighting can produce some of the most dazzling in-camera visual effects available, but Unreal Engine users can actually take advantage of simple green screens as well to bring actors into virtual environments with the same amount of real-time responsiveness.

How to Key in the Unreal Engine

The Unreal Engine uses a specialized compositing plug-in called Composure, which can tackle complex processes such as live keying. While you’ll need an interface for bringing your camera feed into the software (like a Blackmagic DeckLink), integration is pretty seamless with the right hardware.

You can see a glimpse of Composure in action below to create a really effective VFX composite shot of a space station interior.
The ability to change the virtual background’s depth of field with such realistic results is a stunning feature of virtual production, making compositing quick and effective.

The example above uses a clever method of outputting the camera feed into the Unreal Engine, then re-routing the live composite feed from the computer back to the monitor. This allows you to record your live composites directly on the monitor’s SD card, making the process as simple as picking up the camera and shooting.

Now that you’ve seen an overview of what’s possible with Composure, let’s dig a little deeper into the Composure interface and look at how keying and color grading actually works in the plug-in.  
For a step-by-step guide on all the features of Composure and how to get started keying your own shots with it in the Unreal Engine, check out this in-depth video as well as Unreal Engine’s guide to Composure, where you’ll find plenty of documentation to get you started.

How to Track Virtual Camera Motion

So far, you can take the resources provided and achieve a live 2D key in the Unreal Engine, which is great for real-time VFX. Let’s take it a step further!

Now that we've looked at how Composure works to key your footage, the next step is to sync the Unreal Engine's virtual camera movements to match your real-world camera motion, allowing the 3D background environment to move appropriately with your actors. 

Unlike traditional real-time keying, you'd see in a broadcast production with a 2D background (like a weatherman), you can capture dramatic angles, parallax, and so much more as if you're living within the 3D environment.

Currently, there are several ways to track your real-world camera to sync with the Unreal Engine’s camera. HTC Vive tracking pucks or controllers are some of the best options, but if you’re interested in experimenting before spending a lot of cash on more expensive solutions, you can actually just mount an iPhone to your camera.

We’ve talked about how you can use an iPhone or iPad as a virtual production camera without a physical camera, and we can actually use that same process to marry your live-action green screen camera footage with the tracking data from your phone.

As you can tell in the video, using an iPhone in tandem with live-action compositing isn’t the most polished method. Although, for developing your understanding of virtual production techniques and having the ability to actually put all this knowledge into practice, it’s a great path to start out on.
The video above gives a pretty comprehensive look into all the settings needed to link your phone and set up your physical camera feed. The mention of using a relatively inexpensive Elgato capture card as opposed to higher-end video capture interfaces is a great way to break into virtual production without breaking the bank.

As we’ve mentioned before, the Unreal Engine provides a ton of help for filmmakers and VFX artists who want to learn the software on their virtual production hub page.

Be sure to check the ActionVFX blog frequently, as we continue to bring you the latest innovative VFX techniques in virtual production and beyond!  

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