Projection in Theatre – Special Effects

So you’ve been doing projection in your theatre for a few years, projecting some photos and a video or two onto a cyc at the back of the stage, but now you’re looking for something a little more impressive – what can you do? Here’s a few ideas.

Fog Screen

Solid, flat surfaces are really great for a clear projection, but aren’t they a bit dull? How about a surface that people can walk through, which can be created or destroyed within seconds?

A fog screen is created by stage fog or microscopic water droplets caught in a laminar curtain of air. The airflow keeps the fog in a thin sheet for a drop or rise of a few metres. An image can then be projected onto the surface from in front or behind, producing a ghostly illuminated wall through which actors may walk.

There are commercial offerings of the special device needed to create the wall, such as Fog Screen which uses tiny water droplets as the fog. The cost of these systems is very likely out of the range of amateur theatre productions, however. Fortunately there are many people who have made systems that mimic those commercial products. I’d love to have a go at making one, using either a standard fog machine or a high-power ultrasonic fogger (my preference).

It’s unclear whether the noise levels of these systems would prohibit their use in all but the loudest sections of productions.

Motion Tracking

You may have seen or used a Kinect with an Xbox, which allows the gaming platform to capture the motion of individuals standing within a range of a few metres before it. This device uses Time of Flight cameras to measure the time it takes for a pulse of light to travel from an infra-red light source, bounce off a subject, and return to the camera sensor.

Other manufacturers have taken the batten from Microsoft and developed ToF camera products for other systems like the iPad. With drivers like OpenKinect, ToF camera systems can be connected to Linux and Mac machines, which are arguably better options for making video art, although in some cases it can be a little complicated.

They can be used to provide real-time feedback into specialist graphics applications such as Processing to create interactive video art installations or more serious data exploration/analytics applications. There’s few reasons why it couldn’t also be combined with projection in a theatre to create special effects.

Take, for example, a pantomime that includes a fairy. One could combine a projector with camera tracking to create a ‘magical’ sparkling aura around the actor, which follows them about the stage. Combine it with the fog screen for even more awesomeness.

If detailed depth tracking is not required, then a similar effect can be obtained using standard cameras combined with object/edge detection software. They can operate over much larger areas, and the cameras can be positioned well out of the way of the stage, as opposed to ToF cameras which would need to be positioned on the stage due to their limited range. Some systems provide basic depth information by having multiple cameras from many angles to calculate the position of the actor.


‘Passive’ 3D projection, using polarisation, is used in many cinemas to provide the illusion of depth. While many dispute its merits, some suggesting it’s just a gimmick, consider how it could be put to use in theatre.

One could create a virtual extension to the stage, create moving effects which appear to reach out into the audience, or even generate an entire set in a virtual 3D world. The projection hardware set-up would be a little complicated, and the content could take quite some time to create, but the cost per audience member would be tiny – the cost of a set of passive glasses.

There are some questions around how effects may work from the various viewing angles within an auditorium – after all, cinemas don’t ordinarily have multiple tiers and boxes, whereas many theatres do – but it’s something that would be fun to explore.

Projection Mapping

This technique has been used for several years, and involves using projectors on non-flat surfaces such as boxes, spheres an even entire buildings. Software is used to correct the geometry of the projected image such that it appears without distortion on the projection surface.

Projection mapping can be used to create entire sets without a drop of paint – except that needed to create a good projection surface.

There are some challenges around preventing the actors from casting shadows. This can be overcome by limiting the permitted area on the stage and through careful placement of multiple projectors.

While there’s a reduced weight on the scenic department to produce detailed sets, the onus shifts to the 3D artists necessary to create the world to the scenic designer’s vision. Amateur theatres could struggle to find the necessary talent.

Robotic Motion

If you combine Projection Mapping with high-precision robotics, you can achieve some incredible effects, as demonstrated in these videos.

It goes without saying that this is likely outside the capabilities of amateur theatres, but I wouldn’t be surprised if it were seen in large, commercial theatrical productions.

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