Mindblowing particle work in action-packed 3D spot

Creating impressive 3D particle work is anything but easy. But this new spot for multinational steel manufacturing corporation Accelormittal makes it look a cinch. Working in collaboration with ad agency TBWA, VFX and postproduction company SHED created the impressive effects after being approached by the project's director Alexis Durand-Breault.

"The original idea was quite clear, but we did have a lot of artistic freedom," says SHED artist Luc Girard. " Once we received the storyboard, we reorganised it a bit to make sure the different transition would work. We developed the look of the environment, of the metal particles and how all of that moved around."

The team at SHED had a lot of artistic freedom when working on the Accelormittal spot

Animation vs environment

In order to create the complex effects, the SHED team worked out an efficient pipeline. "We designed everything on two fronts at the same time," explains Girard. "On one side we had the animation, or more specifically how the particles would move around to define an object, and on the other side we had the look of the environment because we didn’t want the whole thing to look menacing or like a flock of angry moths.

We did a ‘techCheck’, which consists of a fast-to-render pass with that lets you see all the particles clearly

"For the animation, we proceeded by doing what we call ‘techCheck’," Girard continues. "It consist of a fast-to-render pass with minimal lighting that lets you see clearly all the particles and how they move. As for the look development, we built the lighting and the shading on some still frame, without the particles at first, just to make sure the director agreed with the overall feeling. Once he approved the ‘techcheck’ of the particles, we imported those in the lookdev scenes and made sure he was still happy with the look."

In order to create the complex effects, the SHED team worked out an efficient pipeline

Super simulations

To make all of this possible, a combination of tools from Softimage and Arnold renderer were used, as well as Exocortex’s Slipstream to generate most of the particles movement. "Softimage, with it’s ICE simulation system, and the help of Exocortex’s Slipstream made it relatively easy to simulate those millions of particles in a reasonable timeframe," says Girard. "Arnold on the side made it possible to render those tens of millions of particles and instances without too much of a hit on rendertime and memory consumption.

"I’d say the biggest technical problem we had to overcome was the management of the simulation caching. We ended up with hundreds of gb of data we had to pass around the network between the simulation and the rendering departments. We developed a few in-house tools that helped by transferring locally all those cache and making sure our renderfarm would be synched on the data the lighting artist was using at all time.

The biggest technical issue on this project was overcoming management of the simulation caching

Another technical aspect the team had to deal with was the the spot being a continuous shot without any clear cut. "Even though Arnold let us pack a lot of polygons in a single frame, we did have to make sure we didn’t sample useless objects outside of the current frame," says Girard.

"We used different strategies for that, like deleting a lot of particles once they are out of the camera view, or simply rendering different passes instead of a single one. Those strategies made it possible to have rather quick turn-around when the director or the client had some comment on a segment of the spot."

Want to know more about how the spot was made? Check out this cool making-of video:

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