Experimenting with the Pepper's Ghost Technique

Over the past few weeks, we've been experimenting with an old theatre technique, known as Pepper's Ghost. The Pepper's Ghost technique creates a translucent, animated hologram that appears to sit in three-dimensional space. The effect can be quite compelling and creates an experience in which viewers see what appears to be a ghost hovering in three-dimensional space. When combined with appropriate audio, a Pepper's Ghost can be really memorable.

The Pepper's Ghost that we've had set up at the office has been built by Darryl Rogers from Museum Mechanics. Darryl has a long history of working on stage sets, museum interpretation pieces and interactive art exhibits. Pepper's Ghosts are something of a speciality for Darryl and the video shown below is from an art piece that Darryl has created, which is titled "Water Walkers".

In an ideal world, a Pepper's Ghost is created in an environment where lighting and staging can be strictly controlled. For the purposes of our demo, we didn't control the lighting completely, but nonetheless, we achieved a pretty compelling Pepper's Ghost effect in the Bitlink office.

How the Pepper's Ghost Works

If you've ever seen a reflection of something on your car dashboard, which appears to hover somewhere in the space beyond the glass, then you've seen something like the Pepper's Ghost effect. The technique employs a slanted piece of glass which can be used to create a reflected image that appears to exist in three-dimensional space somewhere behind the glass.

In this video, you can see that there appears to be a man walking on top of a table, somewhere between the frame of the glass and the bookcase in the background. By adding objects into the scene, the effect of the Pepper's Ghost can be enhanced. The structure of the three-dimensional environment around the ghost creates a context that makes it appear more like the ghost is part of a real environment.

Traditionally, Pepper's Ghosts were performed live, with the source of the projection being a real actor who is performing out of the direct line of sight of the audience, but whose reflection can be seen in the slanted pane of glass. One common technique in theatre is to have an actor perform in the orchestra pit, with a slanted piece of glass on the stage which creates the effect of a ghost within the scene.

In our version of the Pepper's Ghost, we are using a pre-recorded video, which is being played on a television that has been hidden below the piece of glass. Pepper's Ghosts can also be created using projectors and other digital sources, which can enable ghosts of pre-recorded actors (as is the case in our demo), as well as entirely digital characters (such as 3D models/characters from animated films).

One of the most compelling things about a Pepper's Ghost is that it's an optical illusion; it's a trick of physics, rather than a trick of technology. Because of this, Pepper's Ghosts that have been created with care and attention to detail can quite seamlessly fit into a scene, or built environment, and can create a believable and memorable experience. For this reason, Pepper's Ghosts are quite popular for use in historic displays (such as having someone from the past talking about their experiences) as well as combining Pepper's Ghosts with live actors (such as during a stage show or concert).

In any case, it's an effect that videos don't really do justice; in reality, the experience of seeing a ghost rendered in three-dimensional space, as part of a larger scene, is really quite impressive. We're hoping we'll have a chance to experiment with this technique some more over the coming months and that a project will come our way that will enable us to deploy some Pepper's Ghosts in the wild.

James Riggall

Launceston, Tasmania, Australia

James is a Tasmanian entrepreneur who found his start as a teacher at the Human Interface Technology Laboratory (HITLab) in Launceston, Tasmania. James worked at the HITLab for five years. During that time, he taught courses in virtual reality, augmented reality, entrepreneurship and video game design. In his teaching career, James worked extensively with international lecturers, including the founder of the original HITLab in Seattle, Professor Thomas Furness. James also helped facilitate many guest lectures from international speakers, including staff from Microsoft, Valve Software and Gas Powered Games, as well as numerous independent video game developers. James left the HITLab in 2012 to establish Bitlink. Bitlink is a technology consultancy and software development house which is based in Launceston. As consultants, the Bitlink team help local businesses get the most out of technology and build their own success in the digital economy. As developers, the team build mixed reality and data visualisation applications for a variety of hardware platforms. James serves as a director of Startup Tasmania, a not-for-profit organisation and networking group for Tasmanian entrepreneurs. James is also one of the key proponents of the Macquarie House Catalyst Project, an initiative which aims to convert an iconic historic building in Launceston into a coworking space for Tasmanian innovators.