Up in Flames
August 26, 2013 1:03 am
Josh Johnson makes fire and smoke look more realistic using C4D and TurbulenceFD
What if there were no volunteers? That is the question posed by a dramatic public service spot created recently by Missouri-based boutique production house, Chimaeric. Josh Johnson was the VFX supervisor and lead artist for the spot, which opens on a fire hose lying uselessly on a dark street as a nearby house goes up in flames. Suddenly, volunteer firefighters appear on the scene, pick up the hose and jump into action.
Woodruff Sweitzer, an advertising agency with offices in Missouri and Canada, contacted Chimaeric (http://www.chimaeric.com) to create the spot. Working closely with the agency’s creative team and director David Anderson, Johnson came up with a plan for blending footage shot by the team with visual effects he would create using Maxon’s Cinema 4D.
As it happened, though, weather conditions and time constraints meant Johnson ended up having to do more things digitally than he had planned. “At first, the agency was a little skeptical about doing a lot of visual effects because they wanted it to be photo-real, but they trusted us and they were very happy about how it turned out,” he recalls.
Location, LocationBuilding an actual house to set on fire was not part of the plan for this project. Instead, Johnson and others on the creative team opted to shoot at a site used by local firefighters for practice. For the home, they chose one of the location’s stone and brick structures that included a working garage door. To make the structure look more like an actual home, the production designer laid sod for an instant grassy lawn and installed a mailbox.
Johnson took this shot while location scouting with Kevin Duggin, director of photography.
Johnson used measurements he took at the location to set up a pre-visualization inside Cinema 4D. After creating some initial proxy geometry, he set up cameras and animated moves using the Motion Camera according to the director’s instructions. “He wanted a camera move with just one shot, no cuts,” Johnson recalls. “So I mimicked how we would do this with a steadicam and that really helped the production team envision how the shot was going to look.” Come shoot day, steadicam operator Michael Wilson nailed the shot by starting out on a forklift and then stepping off while continuing to film.
Fire and Smoke
Though the first scheduled shoot had to be cancelled due to heavy wind and rain, the project deadline could not be moved, so that meant less time for post production. Thankfully, the second shoot was held as planned, though it did rain enough to “add to the atmosphere a bit,” Johnson says. Complicating things further was the plan to light propane fire bars inside the structure to get the effect they wanted. Though it seemed like this would work, no one had yet seen the bars on fire at night. “We had no idea what the real fire was going to look like ahead of time, but we were keen on trying to shoot as much as possible in camera and enhance it in post if we needed to,” he recalls.As the VFX supervisor, Johnson closely monitored all aspects of the shoot and he was happy to see how well the steadicam shot turned out. But one thing he and others noticed right away was the quality of the fire—it just wasn’t realistic enough. He assured the team he could enhance it digitally, and had the director of photography shoot some additional fire elements that could be used for compositing.
Johnson used the C4D fluid dynamics plug-in, TurbulenceFD, to make the fire appear threatening and more realistic than it did on film.
“I knew that a lot of the magic was going to happen during compositing when I would be working with the fire footage we shot and the fire effects I would need to create in Cinema,” he says. Though fog machines were used to help simulate smoke billowing out from beneath the garage door, Johnson found himself needing to pump that up in C4D as well because it dissipated too quickly in the evening breeze.
Johnson's fire simulation setup inside C4D.
Both visual effects challenges appealed to Johnson, who says he’s “always wanted to play with smoke and fire without getting in trouble.” That desire along with always being fascinated with digital FX work prompted him to become a beta tester for TurbulenceFD, a fluid dynamics plug-in for C4D (http://www.jawset.com), and he’s been using it to create fire and smoke effects for the past three years. “The potential to create realistic fire and smoke is really exciting,” he says, pointing out that TurbulenceFD tutorials are available on his website http://www.vfxdaily.com. And he’s currently working on a new introduction to Turbulence FD, too.
Johnson knew that the key to getting the fire to look threatening and realistic was to fill in the calmer parts while making the whole thing bigger. It helped that the rain delay had given him some time to try out a few different fire effects at home prior to the 8-day deadline crunch that followed the shoot. He started by using SynthEyes to 3D track the shot because “you can make the coolest fire in the world, but if it doesn’t sit in the scene, it’s not going to work,” he explains.
Using the f-curve mapping in Turbulence to dial in the shading of the fire.
Testing the fire simulation with the proxy geometry.
Next, he brought the shot into Cinema 4D and built the proxy geometry of the garage, as well as a fire bar similar to the ones inside the buildings on location that he could use as an emitter for TurbulenceFD. Doing this allowed him to see where the fire hits, bounces and interacts with other objects in the scene. “I used the long cylindrical bar object I created as my base to set the fire and then I took the cylinder inside TurbulenceFD and added fuel to make it combustible,” he recalls, adding that it took several simulations to get the effect he wanted. (Watch the VFX breakdown video here: http://www.vfxdaily.com/fire-and-smoke-vfx-for-a-commercial-rd/).
A still from the smoke simulation render as the camera moves through it.
In all, he rendered out about four different fire simulations and combined all of them in After Effects before blending the final file with footage of actual flames. For the smoke, which needed to be fairly subtle, Johnson used the camera track as the camera moved along the ground to set up multiple emitters for TurbulenceFD. A couple of rectangular cube emitters with a high amount of force allowed him to replicate the look of a fog machine. He controlled the opacity of the smoke in post.
After Effects' Roto Brush came in handy when rotoscoping out the firefighters. Johnson also relied on more traditional techniques like luma mattes and mocha.
To put the digital fire into the scene in front of the firefighters, Johnson first used After Effects’ Roto Brush tool, followed by a combination of mocha and luma mattes to rotoscope the firefighters out and put the fire behind them. It was a bit of a challenge, he says, but he’s happy with the way it turned out and so is the client, who didn’t realize until they were told that they were seeing quite a bit of digital enhancement. “When you’re adding visual effects, they can’t be distracting to the audience and it’s very satisfying when people can’t tell what’s real and what you did,” he says.
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August 26, 2013
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