“As far as I am aware, slow motion has never been achieved on an LED stage before this commercial,” says Whiteson. “When running higher frame rates, like 48fps on LED walls, the likelihood of seeing scanlines in-camera becomes more prevalent. However, this is also contingent on your LED panels, cameras, and the movement of these cameras. To achieve the best results, we tested three different cameras at various different frame rates while the wall was running at either 24fps or 48fps.”In the end, the team decided to use the Alexa Mini because it can do 200fps and produces the least amount of flicker. “No other camera other than Phantom could do that for us without cropping in on the sensor,” says Whiteson. “Even at 200fps, we still needed to slow it down to 800fps.”

In addition to the flicker, the team also discovered that the crowd simulation would need to run slower than the original 24fps. Once they shot their first test, it became clear there was not enough information in the crowds movement to withstand the 200fps camera speed, so they prebuilt different speed variations of CG crowd. At any given moment, they could instantly activate one of the animations, depending on the frame rate they were shooting at.

“That’s a huge benefit of using Unreal Engine—to load those different assets at the push of a button,” says Whiteson.
 

Digital 3D crowds for film and TV

As a compositor, Whiteson is often asked to duplicate or generate 3D crowds to fill a stadium—a task that he says is both time-consuming and challenging. “It’s always tedious work,” says Whiteson. “Tracking, keying, or rotoscoping, cloning shot elements, blending in atmosphere—it’s something we are asked to create maybe four to five times a year.”
 
The team at alter ego wanted to provide a cost-efficient solution to clients that would give them the freedom and creativity to tell their story—without huge post implications that tend to follow crowds.

That’s where PXO came in. Earlier this year, the award-winning international visual effects and virtual production company completed over 700 VFX shots for the HBO series Winning Time: The Rise of The Lakers Dynasty

As you can imagine, 90% of the work consisted of CG stadiums and crowd simulations. The PXO team realized there was a need for a faster and more efficient way of doing 3D crowds. In the film and TV industry, ‘faster and more efficient’ often means using game engine technology, so the team developed a flexible crowd tool in Unreal Engine that could not only perform in real time, but be used on LED volumes.

When the opportunity to work on the Caledon Football Club commercial came up, alter ego and PXO knew they had to put this new tool to the test and really push it to its limits.

“PXO and alter ego have collaborated on several commercials,” says Pixomondo Chief Innovation and Chief Creative Officer Mahmoud Rahnama. “After PXO wrapped the first season of HBO’s Winning Time, I told David about the challenges we had creating the VFX crowd sequences using traditional methods. He told me about his challenges attempting to shoot high frame rate shots on an LED wall. That’s when we decided to score two goals with one ball!” 
 

Source: Unreal Engine Blog

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