When director Paul Feig embarked on making a brand new Ghostbusters movie, one of the many challenges he faced would be how to realize a host of supernatural beings. The original Ivan Reitman films had made stunning use of practical and optical effects to bring the ghosts to life. But in 2016, of course, advanced computer generated imagery techniques were available to the filmmakers, and virtually required for a big blockbuster.

The effects team, led by visual effects supervisor Pete Travers, had to approach making the ghosts of the new Ghostbusters (including Slimer and the Marshmallow Man) with two goals in mind: paying homage to what had come before and taking advantage of the newest VFX tools.

Honoring the old-school

The 1984 and 1989 Ghostbusters films were hallmarks of combining practical puppetry with hand-animated effects, matte paintings and optical compositing. That provided a strong base for the visual effects crews on the film (the main companies involved were Sony Pictures Imageworks, MPC and Iloura) to ground the ghost shots in something familiar.

“All of our effects, including ghosts, the ectoplasm and proton beams are heavily inspired by the original film,” Travers told Inverse. “And there is a fair amount of practical effects in the film, not to pay homage, but because it was the best way to achieve the effect. If it ain’t broke don’t fix it…in post.”

Ghosts on the set

In Feig’s film, the ghosts have vapor trails that emit from the glowing creatures. These were called emanations. “Any time we had emanations in the movie,” explains Travers, “we needed a 3D representation to emit off of, therefore all of the ghosts, including the more practical ghosts like Gertrued and the Subway Ghost, had some form of 3D representation. If it was a practical ghost, we always started with roto-mation of the original actor.”

The Ghostbusters encounter Gertrued Sony Pictures

Since the ghosts had to glow, that meant they would also impact on their environment, and that’s where a number of on-set practical solutions came into play. Firstly, every representation of a ghost character on the set had LED lights of some color used to enhance the scene. The solutions ranged from a cast actor (Gertrude and Subway Ghost were played by actors Bess Rous and Dave Allen, respectively) who would be decked out in LED’s sewn into their costumes, or a puppet with LED’s, or even a ball on a boom with LED’s.

Some very creative solutions were employed to help with the interactive ghost lighting. “When the Rock Concert Ghost was flying around the concert hall it was represented by a piloted drone covered in LED’s,” notes Travers. “This way eyelines could be preserved for the hundred of extras. Everybody knew where to look.”

The same approach was followed for the streams of energy shown firing from the Ghostbusters’ proton packs. “We added a LED cap to the tip of guns for interactive lighting, which was triggered by firing the guns so that the actors would be bathed in orange light when they fired the stream, says Travers. “This was also great because the actor could feel the effect of firing the gun.”

Slimer and friends take a new form

Probably the most famous and popular Ghostbusters ghost is Slimer, beloved from the original movies and enduring from subsequent Saturday morning cartoon appearances. But when Slimer began being designed this time around, the visual effects crew found that there had previously been many versions of the character.

“The end result,” says Travers, “was a blend of all of those concepts plus some new details which is only possible from the availability of new technology. We added digital hairs and digital slime, his name is Slimer after all, which we would simulate onto his body. So if he jerked around, slime would fly off of him. Basically if it looked gross, we knew we were done.”

Sony Pictures

Slimer’s performance was informed by an on-set puppet used for basic blocking and, after being draped in LED’s, for interactive lighting. “When it came to the animation,” discusses Travers, “we let the talented folks at Sony Pictures Imageworks and MPC just go off and do their magic. The only criteria that we really gave them was that we wanted Slimer to act like he was crazy, as in, he could go with a rapid volley of emotions in a short amount of time.”

“I told them,” continues Travers, “that in the main shots, I needed to be able to find at least one frame where he was happy, another one anger, frustration, sadness all within one shot. He is a disgusting character, but you have to have sympathy for him at the same time.”

The film sees the return of another classic Ghostbusters character, too, in the form of the Stay Puft Marshmallow Man. With a final villain already part of the storyline, Stay Puft instead makes an appearance during the Macy’s Thanksgiving Day Parade in New York, in which the ghosts are marauding as giant inflatables.

Interestingly, designing those balloons had an unusually familiar origin for Travers. “What we found was that the original parade balloons from the 1930’s were scary enough, almost too scary. So all of the design of the balloons come directly from photographs of actual balloons. We really don’t know what they were thinking back then, considering how creepy they were. I guess parades weren’t for kids back in the 30’s, or maybe nightmares were considered a healthy part of childhood.”

Feig then found a way to incorporate Stay Puft into the parade. “On set,” elaborates Travers, “which was in the financial district in Boston, we used 16’ diameter lit balloons. This gave us a tremendous lighting reference for the eventual digital balloons. Imageworks, led by Daniel Kramer, created the sequence leaning heavily on extremely talented fx animators to create the subtle motion details in the balloons movements and the explosions.”

It was a far cry from how Stay Puft was realized in the original Ghosbusters. There, visual effects supervisor Richard Edlund had incorporated a costumed performer, forced perspective live action sets, miniatures and an array of optical effects to have the Marshmallow Man wreak havoc on New York and then destroy him.

“We all have tremendous respect for the original film and those responsible for it,” reflects Travers. “We wouldn’t be here were it not for the pioneers like Richard Edlund who helped to forge our industry.”