# Acting to a Tennis Ball: Eyelines and Green Screen for Actors

> How actors play scenes opposite a tennis ball on a stick, an X of tape, or nothing at all: why the eyeline matters more than anything, how to build the thing you can't see, how to time reactions to dialogue you'll only hear later, and a home drill with Macbeth's dagger.

- URL: https://www.offbook.com/blog/acting-to-a-tennis-ball-green-screen
- Published: 2026-10-20
- Last updated: 2026-10-20

The scene says a dragon lands in front of you. On the day, there is a green wall, a crew member holding a pole, and on the end of the pole, a tennis ball. Someone says, "That's his eye. He's angry. Action."

Every actor who works on screen long enough meets some version of this. It might be a creature, a crowd that will be added later, a twin you play yourself, or just an X of tape beside the lens in a self-tape. The problem is the same each time: you have to see something that isn't there, see it in the same place every take, and react as if it matters.

The short version: the eyeline is the job. Find out exactly where the thing is and keep your eyes there. Then build what you're looking at in detail, so your face has something real to respond to. Learn the timing of what it says or does, because a late reaction gives the trick away. And practice at home, because none of this is mysterious. It's a skill, and it gets better with reps.

## Why the tennis ball exists

Visual effects teams use tennis balls because they're easy to get and easy to tape to a pole, and they solve one problem: they tell the actor where to look. A piece on [the tennis ball as an unsung hero of visual effects](https://beforesandafters.com/2023/03/04/meet-the-true-unsung-hero-of-visual-effects-the-tennis-ball/) collects examples. Supervisor Scott Squires used ping pong and tennis balls on *Dragonheart* and admitted, "Trying to get actors to look where you need them to is always an issue." On *Game of Thrones*, Joe Bauer describes the young dragons as tennis balls on sticks, moved during the take so Emilia Clarke had something to react to.

Notice what the ball is not. It isn't a performance aid in the acting-class sense. Nobody expects you to find the tennis ball moving. It's a coordinate. When the creature is added later, it has to sit exactly where your eyes went, or the shot falls apart.

That's why the crew cares so much. On *Legend*, where Tom Hardy played both Kray twins, VFX supervisor Adam Rowland told [fxguide](https://www.fxguide.com/?p=183839), "The most important thing to get right is eyelines." For one pub scene, the team built a rig of numbered tennis balls so Hardy could look at a different spot at different beats of the dialogue.

## Get the eyeline exact, then keep it

If you take one habit from this article, take this one: before the first take, ask where the thing is. Not roughly. Where is its face? How tall is it? Does it move during the shot, and if so, when and where to? The ball, the X, or the crew member's hand will show you, but ask about the moments between marks too.

Then lock it in. A **look point** only works if it's the same every take, because the editor will cut between takes and the effect has to line up with all of them. Pick something precise to aim at: not "the ball" but the top-left edge of the ball, roughly where an eye would be. If the marker comes out for a clean take, find a tiny landmark behind where it was, such as a scuff, a seam, or a bolt, and use that instead.

Height matters more than people think. A creature twice your size means your chin comes up, and your neck shows it. A child or a dog means you look down, and your lids lower. Check that you're looking at the right height for the eyes, not the middle of the body. A glance at the chest of a nine-foot creature reads as a person staring into space.

### When there are several things to look at

The same rules carry over to a self-tape with imaginary people in the room. StageMilk's [guide to eyelines](https://www.stagemilk.com/a-guide-to-eyelines/) suggests keeping your reader on one side of the lens and putting the imagined people, places, and things on the other side, and starting with just two or three eyelines. Plot them before you shoot, rehearse them, and don't move them once you've chosen. If your character talks about a brother who isn't in the scene, he lives in one specific spot, every time.

Our guide on [where to look in a monologue](https://www.offbook.com/blog/where-to-look-in-a-monologue) goes further into placing an imaginary listener, and [acting for shot sizes](https://www.offbook.com/blog/acting-for-shot-sizes) covers how close to the lens your eyes should be as the frame tightens.

## Build what you can't see

A fixed eyeline gets the shot technically right. It doesn't make you believe anything. That part is still acting, and it's harder than usual, because green screen takes away the cues you normally lean on.

A 2013 dissertation from the University of Pretoria, [on actors working with green screen](https://repository.up.ac.za/handle/2263/33361), puts it plainly: the technology limits or removes the outside stimuli that help an actor believe in a scene. Its proposed answer is old and simple. Stanislavsky's *magic if*: what would I do if this were really here? The work is to answer that question in enough detail that your body responds.

So build the thing. Before you shoot, decide what it looks like up close. What color is the dragon's eye, and how wet is it? Does it smell? How warm is the air when it breathes? Is it hurt, curious, about to strike? You don't need to share any of this. You need it to be specific enough that your eyes stop searching and start seeing.

This is the same muscle as sense memory work with imaginary objects. If you've never done that kind of exercise, our walkthrough of [Uta Hagen's object exercises](https://www.offbook.com/blog/uta-hagen-object-exercises) is a good place to start, and [given circumstances](https://www.offbook.com/blog/given-circumstances-in-acting) will help you fill in the world the effects team is going to paint around you.

### Let the thing change you

A common mistake is to build a vivid image and then stare at it. Real attention moves. When a person is talking to you, your eyes shift between their eyes, their mouth, and whatever they're holding. A creature has parts too: a claw that twitches, a tail behind it, a wound on its side. Let your gaze travel inside the space the thing occupies, then come back to its face. That small movement is often what makes a reaction look alive instead of fixed.

## Time your reactions to dialogue you'll hear later

The hardest part of acting to nothing is often not the seeing. It's the timing. If the creature roars and you flinch a beat late, the audience feels it, even if they can't say why.

Productions handle this in different ways. On *Legend*, fxguide reports, Hardy heard his other twin's lines, recorded earlier, through an earpiece, so he could react to them while playing his own side. On other sets, someone may call out the beats. On some, you get nothing and have to count.

So learn the other side's lines and actions as well as your own. Know how long the roar lasts. Know whether the other character pauses before their answer. When you know the shape of the scene, you can wait for a line you can't hear and respond on time.

You can rehearse this timing at home with Offbook. Upload the scene, pick your role, and realistic voices read every other character while it listens and plays the next cue when you finish your line. As the video below shows, you can set how fast the other voices speak and add a pause before a line, so you can rehearse reacting into a silence where the creature's roar will go.

Video: [Pacing](https://www.offbook.com/learn/pacing) (1:09)

## A home drill: Macbeth's dagger

Shakespeare wrote one of the great tennis-ball scenes four centuries early. Macbeth sees a dagger that isn't there, reaches for it, and can't hold it. It's perfect practice, because the text tells you exactly where the object is and what it does.

> **MACBETH.** Is this a dagger which I see before me,
> The handle toward my hand? Come, let me clutch thee:—
> I have thee not, and yet I see thee still.
>
> *William Shakespeare, Macbeth, Act 2, Scene 1 ([Project Gutenberg](https://www.gutenberg.org/ebooks/1533))*

Here is a routine to run with it, or with any scene where you see something imaginary:

1. **Set the mark.** Stick a small piece of tape on a wall or a stand at the height where the dagger hangs, about an arm's length in front of you and a little to one side of your phone's lens.
2. **Build the dagger.** Decide its length, the color of the handle, and whether the blade catches the light. Note which way the handle points: the text says toward your hand.
3. **Run it with the tape.** Say the three lines five times, keeping your eyes on the exact spot each time. On *come, let me clutch thee*, reach, and let your hand close on nothing.
4. **Peel the tape off.** Pick a tiny landmark where the tape was and run it five more times. This is your "clean take."
5. **Film it and watch back.** Does your eyeline land in the same place every take? Do your eyes look as if they see something specific, or do they drift? Fix the one that wandered and go again.

Then make it harder. Have the dagger move: on *I see thee still*, it has drifted a few inches to the left. Your eyes have to follow it to the new place and stay there.

## Keep it in proportion, and keep your head

It helps to know that even great actors find this hard. Ian McKellen has described shooting parts of *The Hobbit* alone on a green screen with photographs of the dwarves on stands for company. According to [The Mary Sue's report of the interview](https://www.themarysue.com/ian-mckellen-hobbit-cry/), he cried and said aloud, "This is not why I became an actor." If it feels strange to you, you're in good company.

It also helps to remember how much the rest of the team is doing. When *Wimbledon* was filmed, the [Christian Science Monitor reported](https://csmonitor.com/2004/0917/p11s02-almo.html) that the actors mimed nearly all the major tennis action and a digital ball was added in postproduction. The effects team carried the ball. The actors carried the effort, the focus, and the fear of losing. That's the usual division of labor on an effects shot.

Your part is smaller than it looks and more important than it feels: the right spot, the right height, the right moment, and a mind that believes what it's looking at. If you'd like more on the technical side of a set, our guide to [hitting your mark on set](https://www.offbook.com/blog/hitting-your-mark-on-set) covers marks and matching continuity, which come up on effects shots too.

## Questions actors ask

### How do actors act to a tennis ball?

They treat the ball as a precise eyeline, usually the eyes of whatever will be added later, and build a detailed picture of that thing in their imagination. Then they keep their eyes on the same spot every take and time their reactions to what the creature or character does.

### How do you keep a consistent eyeline on green screen?

Ask exactly where the thing is and how tall it is, pick a tiny precise point to look at, and use the same point every take. If the marker comes out for a clean take, find a landmark behind where it was. Rehearse any moves so your eyes travel the same path each time.

### How do I react to something that isn't there?

Decide in detail what it looks like, sounds like, and wants, and let your eyes move around it the way they would with a real thing. Know its timing as well as your own lines, so your reaction lands on the beat instead of after it.

### Where should imaginary characters go in a self-tape?

Keep your reader close to one side of the lens and put imagined people and things on the other side. Choose a few clear spots, plan them before you film, and keep them in the same place for the whole tape.

### Can I practice green screen acting at home?

Yes. A piece of tape on a wall, a phone camera, and a scene with something imaginary in it are enough. Drill the eyeline with the tape, take it away, and check the footage for drift.