Why the humble tennis ball has an ace role on film sets, and beyond.
Yesterday, Shazam! Fury of the Gods director David F. Sandberg tweeted a fun behind the scenes image from his upcoming film. It was of a unicorn-like stuffy head, complete with a tennis ball covering the pointy end of the unicorn’s horn.
While it may have been placed there for (obvious) safety reasons, tennis balls are actually quite a common sight on film sets, often for more than just protecting actor and crew members from sharp pieces of kit. Tennis balls regularly serve as ‘stand-ins’ for the eyelines of creatures of characters which might be added in later in CG by a visual effects studio. Plus, tennis balls have, over the years, played an important role in acting as tracking markers around interior and exterior sets.
Why are tennis balls used so often for these purposes? Well, one reason is they’re incredibly easy to acquire (just go to any sporting store and in fact almost any supermarket). Another is that they can be cut up, shaped, painted on, and twisted and taped around poles and sticks quite easily. They’re also soft! A grip or VFX data wrangler holding a tennis ball on a stick up against a real actor and accidentally dropping it on their face won’t do (too) much damage.
So, to celebrate the amazing and often unsung achievements of the tennis ball in filmmaking and visual effects, befores & afters is looking back at how practitioners have utilized the sporting accessory over the years. We even got in touch with a few VFX supes to reminisce about how and why they incorporated tennis balls into their work on projects such as Dragonheart, Alice in Wonderland and Game of Thrones.
Let’s take a swing at some of those projects now…
The Witches of Eastwick
This 1987 George Miller film features a tennis match in which a magical ball makes it own moves on the court. ILM handled the visual effects work, but since this was right before the influx of digital effects, the approach involved filming an actual ball against black velvet on a motion control mover, and transplanting the footage via an animation stand and pin-blocking. It was then optically composited into the plates of the actors ‘miming’ tennis strokes. Above is an image of the actual ball prop available from The Prop Gallery (and it looks like you can still pick it up for a sweet £1,245).
Visual effects supervisor Scott Squires: “We used ping pong and tennis balls on Dragonheart when Draco is laying down. Trying to get actors to look where you need them to is always an issue. Even pre-digital or CG there was a need to get people to focus on a specific spot. It’s bad when you see a group of people looking in different spots. Many cases we work with special effects, depending on the requirements. The scale, and what type of movement is required, determines what you’ll use on set. Is it standing, jumping, running? It only works at a certain size or it becomes impractical. Ideally you keep it in shot but if you have a man holding or a bug base you’ll have to remove it so you sometimes to run through and actors get the eyeline to something in background to avoid removing. Removing pre-digital was more difficult of course.”
A landmark moment in virtual sets and intricate match moving and tracking was Cinesite’s visual effects work for Space Jam. In this fascinating post from Cristin Pescosolido, lead computer graphics camera matchmover at Cinesite on the film, we learn about the role of tennis balls as part of the VFX studio’s tracking efforts.
“Our first generation tracking markers developed at Cinesite were incredibly simple: regular lawn tennis balls that had been painted red. They were fastened at precise 4’ intervals (1.219 m) to the painted green screen wall. On the floor, we used flat vinyl stickers of the same diameter as the tennis balls (6.6 cm) also along the same precise 1.219m grid. The texture of the tennis ball was hard to describe, as it was slightly fuzzy, just like a tennis ball, but had paint particles on it forming tiny blobs and gooey looking sections. The first movie we used them on was “French Kiss” (1995) followed by “Under Siege 2″.
The markers having a known position could be used by our matchmoving software (mooVtracker) to calculate camera position based on only four points. To do this, it needed to know the exact positions of the markers, thus the precise grid layout. On most shots, we could calculate the camera at almost 24fps for near-real playback to judge our tracking. You can see the column/row markers (0, 1, 2, 3) in the still you sent me that help identifying which row we were seeing. I supervised a team of almost 20 matchmovers, none of whom had used the software before, or even done matchmoving, as it was very new.
After Space Jam, I designed a 15cm cross made of 5cm wide blue screen material, and we either used self-adhesive material to stick it to a hard green screen, or we used velcro hooks to stick them to green screen fabric. The 15cm blue screen cross gave us a similar target we could track using our center-of-mass tracking algorithm, and we could often use keying software to remove them from a background without having to paint as much as we would using red markers. We ended up using the cross markers on most other shoots, most notably “Sphere” and “Jerry Maguire.” Many people still use blue fabric crosses for tracking markers to this day.”
Alice in Wonderland
Visual effects supervisor Ken Ralston: “On Tim Burton’s Alice In Wonderland, I put a century stand in front of Johnny Depp and asked if he needed something better like a real actor or stand in to do the scene. He said he preferred tennis balls to many actors he’s worked with…”
Game of Thrones
Visual effects supervisor Joe Bauer: “When Daenerys’ dragons were 3’ long they were tennis balls on sticks. I would perform their movements during a take with some idea of what the eventual dragon performance might be. This gave Emilia Clark something to react to in her performance. Later when the dragons were 8-12’ long we had accurate sculpts of their heads and necks executed and these were mounted on broom handles. Once again I, joined by VFX producer Steve Kullback, would puppeteer (term used extremely loosely) the heads through the set, supplying the camera operators with Oscar-winning subtleties of lizard emotion(!). As the dragons continued to grow we were able to mount a much lighter weight head on a counter balance. By season 7 we told the camera operators ‘just pan left and widen out 20% and watch this handy previs!’ Other processes like N-cam eventually took over for the trusty ball-on-stick approach.”
Tom Hardy plays both Ronnie Kray and Reggie Kray, twin London gangster brothers in Brian Helgeland’s Legend. To handle the ‘twinning’ shoot, visual effects supervisor Adam Rowland relied on an intricate C-stand-slash-tennis ball contraption to stand-in for the actor (and surrounding actors) for A and B plates, with Nvizible (now Nviz) handling the VFX work. Here’s my story at fxguide about how it was done.
An American Pickle
VFX supe Adam Rowland and Nviz again lent their tennis ball-related stand-in skills to Seth Rogen’s An American Pickle, where the actor had to play against his lookalike in several key scenes. This befores & afters article breaks it down, noting that a stand-in actor was mostly utilized, “however, when certain interactions were required that had to be pixel-accurate, the team would rely on a C-stand/tennis-ball so that Seth would be able to reliably hit his mark in space, be it a glance or something more physical.”
Spider-Man: No Way Home
During several moments in the freeway fight between Doc Ock and Spider-Man in No Way Home, the on-set visual effects team relied on tennis balls to stand in both for a CG Spidey himself and for one of Doc Ock’s tentacles. Digital Domain would later carry out the VFX work. Check out this befores & afters breakdown, revealing that even the most recent and complicated visual effects sometimes still goes ‘old-school’ with the great tennis ball.
All hail the mighty tennis ball. If you have any fun on-set stories about tennis balls and visual effects, please share them in the comments.