This delicate work, as well as the complex CG 'Smart Hulk' and Thanos, was revealed Monday by the VFX team at the CG confab SIGGRAPH.

An estimated 3,000 delegates on Monday attended a panel at the CG confab SIGGRAPH on Avengers: Endgame's visual effects, which including the creation of a CG "Smart Hulk," Thanos and approximately 200 aging and de-aging shots.

Marvels Studios VFX producer Jen Underdahl kicked off the session with the numbers: Endgame had 2,698 shots in the movie, and 2,496 of them involved VFX.

A total of 14 VFX houses contributed to the film, and VFX supervisors from a few of those companies offered a glimpse at the work, including a presentation by Industrial Light + Magic VFX supervisor Russell Earl, who took the audience behind the making of "Smart Hulk."

Earl explained that the process involved bringing together "the right amount of Mark Ruffalo and the right amount of Hulk." Getting the look and performance right also involved scans of the actor, facial capture and hand animation, as well as concept art as reference. It also involved proprietary software including ILM's Medusa facial capture system.

Earl related that ILM started to develop the character when it was working on Avengers: Infinity War, but the story dictated that he wouldn't appear until Endgame. "We learned from the development that we wanted to keep the nuance in [Ruffalo's] performance," he said. "The key was giving animators the ability to tweak the performance."

Digital Domain VFX supervisor Kelly Port and Weta Digital VFX supervisor Matt Aitken described how they furthered their work on Thanos from Infinity War, for instance with Weta incorporating new proprietary software to put more detail in the face.

Weta's Aitken also showed the work on the digital prosthetic for Tony Stark's (Robert Downey Jr.) emotional death scene. "It had to look lethal, but not to the extent that it didn't allow Tony to keep his dignity," he explained.

Roughly 200 shots in the time-traveling story involved delicate aging or de-aging techniques, provided by VFX house Lola, which didn't have a representative on the panel. Those processes were used on actors including Downey and Chris Evans.

Also during the session, Gerardo Ramirez, visualization supervisor from The Third Floor, offered a look at the pre- and post-visualization work.

SIGGRAPH runs through Thursday at the Los Angeles Convention Center.