A Brief(ish) History of Rodney the Robot
by creator Bob Mottram

Visit Rodney's Website

From humble beginnings
In the spring of 2001 I was rather bored
and wandering around in York city centre pondering over whether I should buy some new socks or not.  York is an ancient city, founded in 78AD as a Roman fortress. 
Its inner parts are still surrounded by
a very substantial stone wall designed to keep the unwashed rabble of ancient Britons at bay.  As the centuries
passed by each generation added its
own embellishments and scars.  Columns, castles, a huge cathedral and all manner
of ornate buildings.  As I wandered around in the dreary weather I was wondering whether it would be possible to build a digital version of York in my computer – a reasonably accurate 3D respresentation
of what the city was like at the turn of the new century.  I could take photographs, make measurements from them and painstakingly build up 3D models, but this would take an extraordinary effort.  Maybe I thought I could just attach a pair of cameras to a laptop and wander around the centre of town taking stereoscopic pictures, which could then somehow be automatically assembled into 3D models. 

In the field of photography space really is the final frontier.  Photographs are flat two-dimensional things, but real life has a third dimension giving it depth and shape.  As I look at a cathedral my left and right eyes see it from a slightly different position, and my brain uses the difference between the two images on my retina in order to judge how far things are away, giving me an impression of three dimensions instead of just two.  This is why just looking at a photograph or a movie screen (no matter how large) doesn't give you the same sort of experience of actually being there in person.

So I bought a couple of webcams and played around with them.  It soon became obvious that I needed some kind of fixed structure to hold them both in place whist the photos were being taken, so I decided to build my own pan and tilt mechanism similar to the types of thing on which security cameras are mounted only on a smaller scale.  I measured the distance between my own eyes – about 7cm – and mounted the cameras the same distance apart.  I also needed some kind of approximately box shaped stand upon which the camera mechanism could be mounted. 

That summer I did a few vision experiments using the stereo platform and a laptop computer borrowed from work to take photos of buildings.  I probably must have looked rather odd, but then I've seen far more peculiar sights in the centre of York.  My attempts to reverse-engineer the architecture of the city into 3D models wasn't an immediate runaway success.  In fact the problem turned out to be far harder than I'd appreciated.  Finding matches between the images of the two cameras – something known as “stereo correspondence” – wasn't easy to do automatically, and even worse than this the cameras didn't have enough resolution to judge distances more than a few metres away.  I could have made the separation between the cameras larger, but the problem of correspondence – basically a software programming problem – still remained no matter how I rigged up the hardware. 

So I gave up on the idea of trying to reverse engineer buildings and downsized the problem somewhat in scale to the size of my computer desk.  In this miniature scale domain I could test out different stereo algorithms far more quickly and easily, and with fewer curious looks from passing Japanese tourists.  Instead of a bridge or a large hotel the objects to be observed would be domestic items such as cups or kettles.

It was probably at this point that Rodney came to be born. 

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