Doctor Who. He'd be nothing but an incredibly brainy (if strangely dressed) bloke with two hearts and an attitude if not for his TARDIS. The TARDIS is a combination time machine and spacecraft that can poke into virtually any nook or cranny in the entire history of the Universe. Aside from the marvelous transport capabilities, the most notable thing about the TARDIS is that "It's bigger on the inside!" – a running gag throughout the show. Now, Greg Kumparak has produced an augmented reality model of the TARDIS that produces a remarkable illusion, making the TARDIS indeed appear to be bigger on the inside.

Greg, a more than averagely skilled IP pro, had some time on his hands, and decided he would build a model TARDIS to put on his desk. After accomplishing that, and installing a flashing light on top, he sat back and thought about how neat it would be to make it appear as if the inside were bigger than the outside. When he got a hint of an idea for using augmented reality, he was hooked.

Greg's TARDIS in a late stage of construction (Photo: Greg Kumparek)

Greg used Blender, an open-source 3D computer graphics software program, to make a likeness of the interior of the TARDIS as it appeared in the first years of the rebooted TV series (2005-2010). He then used the Unity game engine together with the Vuforia augmented reality software development kit to insert the image of the inside on the open doors of the TARDIS model.

Vuforia enables the creation of Augmented Reality applications. It can track image targets and some simple 3D objects (such as boxes) in real time using computer vision technology. This tracking information allows a developer to position and orient virtual objects (such as a 3D model of the TARDIS interior) in proper registration with the real object being tracked. As a result, from the viewer's perspective, the real and virtual objects appear as parts of the same object.

The software needed an identifiable surface on which to lock. Originally Greg wanted to use the front face of the TARDIS, but the shadows and changing perspective of this non-flat surface confused the software hopelessly. Then he tried using a small white sign on the TARDIS (reading "Free for use of Public"), but it was too small to get proper orientation. In the end, his solution, which you can see in the video below, was to make the front door removable, and place a sheet covered with unique designs whose image would completely inform the software about position and orientation changes.

That left the problem of rendering the interior image only in the space defined by the orientation sheet. Greg used a method called depth masking to accomplish this. Depth masking is a drawing technique for hiding parts of one or more layers. For the TARDIS, Greg hid all parts of its interior except in the region of the open doors.

As you can see in the video below, the result is quite remarkable. Greg has been inundated with requests for the software, as well as offers of support for manufacturing the TARDIS and similar models. He is currently determined to polish up his methods and make the result available through some mechanism (as yet undefined). As a Whovian and an augmented reality fan, I would run out to buy one!

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