The art of tracer fire

More behind the scenes of the visual effects of Wolf Hound.

Last week at befores & afters, we talked to Turncoat Pictures visual effects supervisor Ryan Urban about the making of WWII film Wolf Hound and its use of real vintage aircraft.

This week, Urban is back to go deeper on the creation of tracer fire added to the real aircraft photography. Here you’re learn about the tracer system developed in Houdini, and about the compositing work involved in Nuke to make the tracers feel as visceral as possible.

Original plate. Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Final shot. Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: How did you create the tracer fire and how did it come to be?

Ryan Urban: Once we reviewed the edit with director, Michael B. Chait, we knew the aerial combat tracer fire was going to be one of the biggest asks needed for the film. We needed to come up with an approach that worked across all the tracer shots and sequences. The first order of business was to figure out the tracer timing and design the look and feel. We kicked off postvis and our FX team.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

The beauty on Wolf Hound was that most shots that needed tracers featured in-camera WWII planes. We could focus our efforts on the added muzzle flashes and CG tracer fire and didn’t have to worry about dialing in any CG planes or CG environments.

b&a: How did you create the tracer look and work out the timing?

Ryan Urban: Our FX artist, Anthony Morrelle, first developed the tracer system in Houdini without any shots in mind. We needed a setup that could operate and respond to variables. It was really cool – it was almost like a video game with a trigger and targeting system. While he was working on his setup, we continued onward with postvis.

Tracer motion test.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: Can you elaborate on the timing and postvis?

Ryan Urban: Before diving in to the details of a shot, we wanted to make sure we fully assessed the sequences’ needs and asks. We utilized a few rounds of postvis on the tracer fire sequences. We made a small library of temp effects to drag and drop for postvis. Tracers zipping by, sparks, and muzzle flashes. Postvis helped us align with Mike’s vision and made sure we were telling the key parts of the story.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

It also helped push the timings farther along before we dove too deep into the polished VFX work and burned through resources. We could really see what was working across the edit and what was specifically needed for each shot.

The postvis helped clarify the complexities of each shot. We flagged each shot and broke them down into tiers. The top tier might be the most complex and require tracked camera, matchmove of the plane and more comp days, whereas the lower tier might be more suitable for a 2D only approach in comp.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

We brought on OPSIS to help with the tracking and matchmove. Michael G. Jackson tracked most of the shots.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

Once Anthony’s FX setup was complete and match moves started coming in, we moved the FX R&D into actual shot work. We picked a few hero shots to run through the ringer to see what worked and broke so we could tweak before pushing out to all the shots.

FX renders were passed to comp, where the final look was refined and polished. After nailing down the approved look, we re-tooled our setup into a Nuke template that could be used to kick off each tracer shot. This was key to help establish certain parameters and maintain a consistent look across shots and multiple artists.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: How did you give each shot its own unique look while keeping the sequence feeling cohesive?

Ryan Urban: Similar to how the production shot multiple takes of the planes in the air, the clouds and lighting would slightly change from take to take. Mike and I loved that. As the edit progressed, those imperfections to the environment felt more real when you don’t have full control over everything in the frame. So we leaned into that with the visual effects. ‘What if the camera didn’t always catch the same moment of tracers?’ With the postvis, we quickly identified where this was working really nicely and then we carried that mindset through the final shot work.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: Can you elaborate on the final shot work?

Ryan Urban: While each tracer shot was technically based on the Nuke template we created, we had some logistics and creative hurdles to sort out. We referred to the postvis often since it was a visual cue the director and I could point to. As a result, the idea of ‘what if the camera didn’t catch the tracers on this shot?’ or ‘What if only muzzle flashes were seen on this one?’ worked really well to enhance the sequence.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

Our hero Nuke template had everything an artist needed to make the tracers work and look like the previous shot. By building it in a modular fashion, we could identify certain shots and easily say, ‘Let’s turn that portion off for this shot’ or ‘Let’s only use section for this shot.’ For instance, we ditched the tracers in the first shot in the sequence. It became only muzzle flashes and some heat distortion trails. We felt it was too soon for an audience to get all of that from the start, and better to hold back a shot or two and ease them into the aesthetic without losing the intensity.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: Can you clarify the lower tier shots vs the higher tier shots?

Ryan Urban: The higher tier shots needed a camera and matchmove and shot specific FX renders. For their renders, FX would customize the timing and render. The timings were based off of the postvis or an early version of the comp that had the muzzle flashes added.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

For the lower tier shots, they remained with the comp team. No cameras, matchmove or specific renders. We had FX create a library of generic renders – side single burst, three bursts, angled, from the top, etc. Then the comp team could march ahead while FX focused on the higher tier shots that required complex, shot specific setups and renders.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

b&a: The tracers make impact. How did you manage to show the damage?

Ryan Urban: Special effects coordinator Matt Stratton and his team handled all things pyro, full scale and miniature, squibs and guns.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

A handful of shots in the opening aerial scene show the destruction of the wings in great detail.
Matt’s team built a facade of the wings and hit them with squibs and sparks. This showed some great in-camera sparks and squibs. We then used visual effects to connect those shots to the wider shots in the air. Adding in a digital tracer that made the impact.

Similarly, his team triggered some blood squibs and shattered glass. We added in the tracers as if it was what caused such destruction.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

During the strafing run, there were a lot tracers making impact. At this point, we already had our existing tracer setup from the two aerial scenes. What was unique about the strafing run was that it called for even more specific timing. Since there were a lot of practical charges going off, we had to hit those to help sell the effect. Anthony reengineered his tracer setup, and built it so the frame of impact could be the variable entered in. Then the tracers launched in reverse back into the plane that was firing them. It was a very handy methodology to art direct the timing and the scene.

Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.
Copyright © 2022 Wolf Hound Productions, LLC. All Rights Reserved.

Wolf Hound is available now on all streaming services, including Amazon Prime Video and Apple TV, and on Blu-Ray and DVD at Amazon, Walmart, and Best Buy.

Brought to you by Turncoat Pictures:
This article is part of the befores & afters VFX Insight series. If you’d like to promote your VFX/animation/CG tech or service, you can find out more about the VFX Insight series here.


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