hannah dee

Soapbox Science, Cardiff

Soapbox Science is a public engagement event designed to get scientists out into the public and into public spaces, talking about their work. It’s supposed to demystify science (a bit) but also to change people’s perceptions of what scientists look like; one of the ways it does this is by making all of the scientists on the soapbox women. When I heard about it, I thought… Public engagement? Women in Science? Sounds a bit mad? Guess I’d better apply then!

The event I applied for was my nearest one, this year, and that was Cardiff, and it was yesterday. As you can probably guess from the blog post, I got in.

Having got in, my next problem was what to talk about… for 30 minutes, to a general passers-by kind of audience, without computers or posters or anything like that. As a vision scientist, who works with computers, that’s quite the challenge. The topic I settled on was Shadows.

One of the cool things about Soapbox Science is that it’s OK to bring along props. Some of the scientists had brains, or little bits of gold, or fungus, or felt-and-wax artistic renderings of tumours (no, srsly, they did). I went for an arduino powered cardboard box.

This involved having a neopixel ring inside a cardboard box, programmed with various lighting patterns, and a button on the outside which switched pattern every time the button was pressed. My hope was that by having a ring-shaped light source it would be possible to look out of the middle of the ring, and having the viewpoint of the lightsource (as Da Vinci said, “No luminous body sees the shadow it casts” or something like that). But the viewpoint was just out so you could actually see the shadows anyway. So I made the 16 light sources either chase around with different colours, or gradually illuminate making the shadows hazy, or gradually go off, making the shadows sharp again.

Inside the box I hung a small plastic model of a skateboarder, I soldered all the bits together, and then I had my main prop: a Shadowbox. The shadow effects created really were quite strange, and they served quite well to illustrate the idea that the size of the light source, the colour of the light source and the colour of the screen all affect the shadow’s appearance.

As you look into the box through one of two holes, the experience of seeing the shadows is quite disconcerting, and it can take a while to work out what exactly is going on. But that’s OK – I wanted something kind-of “installationy” and this worked quite well as a visual experience. What didn’t work so well was the skater on a string – as the figurine was suspended from the lid using fishing wire, she swung wildly from side to side if anyone knocked the box, making it all just that little bit more incomprehensible.

The other props I took were some flipbooks, made from a 50 frame sequence of shadow video. I took books representing the input (the actual video), the ground truth (what we want our software to output), some intermediate processing steps and the final output of our shadow detection routine. These were hacked together using python and LaTeX; if you’re interested in any of the code (flipbook code or arduino code) you can find it on my github account. I also took some zoom in crops of images showing pixellated shadow or non-shadow regions, mainly just to show how hard it is to detect shadows when your input is pixels. And I took some sharpies and a sketchbook because … I NEEDED PROPS.

So yesterday, Saturday morning 4th June, I got up early and drove down to Cardiff with a boot full of electronics and poorly put together flipbooks. I arrived just after 12, to a control centre in Yr Hen Llyfrgell which was a hive of activity, helpers, organisers, mascots, labcoats, tshirts, props and of course scientists. And balloons. And coffee. Each scientist was allocated a helper to assist with props and so on: my helper was a very nice and efficient Cardiff Uni medical student called Gunjan who was awesome at ensuring I had the things I needed when I needed them.

One of the mascots was the Cardiff University Dragon, who’s called Dylan. Apparently it was really very hot indeed inside the dragon. The other mascot (who I didn’t get a photo of) was a teddy bear. I’m not sure why.

We’d been advised to have a few 5-minute ideas for talks, and we’d been told we might get questions/heckles and so on, so repeating bits was probably going to be necessary. The time came and I went out, with this written on the back of my hand:

  • Me and science
  • Shadow formation
  • Computer vision
  • Pixels, videos
  • Ground truth
  • Colour, texture

Our soapboxes were in a busy intersection on Cardiff’s shopping district, quite near a woman with an amplifier singing eighties lounge songs (niiice). As talk venues go, I can’t think of many more challenging. The actual “talking about science to the general public on a soapbox” bit was almost exactly as terrifying as I thought it would be.

For the first half hour session, I stood up, talked, drew an audience of about 15, caught people’s eyes, talked some more, waved my props around, tried to get people to look into the shadow box, and then ran out of things to say. Looking at my watch I realised I was just 2 minutes from the end of the session, so that was OK and the audience did have questions. Most of them had stayed till the end, too. They might have had even more questions I suppose, if I had at any point slowed down enough for them to get a word in…

During my second stint on the box, I had a completely different experience. For the first 5 minutes I had no audience, and then a guy I vaguely recognised (maybe from the Crucible?) came and watched at the request of one of the organisers. Which was nice. I didn’t really want to talk to an audience of 0. Slowly more people came and went, including some kids (who really liked the flipbooks) and a remarkable heckler who thought I was a bloke.

At the end of the day everyone was quite hyper, and we all agreed it had been super fun if terrifying. Here’s a picture of me with my excellent helper Gunjan:

At this point I needed to stretch my legs and be quiet for half an hour so I went and checked into my hotel before returning to the afterparty (complete with wine, for those who do that sort of thing). All in all a good day. I’m not sure that it’s my favourite form of public engagement, but it certainly got me out there and out of my comfort zone, talking to people who I’d never had spoken with otherwise.

Building a lightstage

A Lightstage is a system which lets you completely control illumination in a particular space, and capture images from multiple views. They’re used for high resolution graphics capture and computer vision, and they’re fairly rare. I don’t think there are many non-commercial ones in the UK, and they’re research kit (which means you can’t really just go out and buy one, you’ve got to actually build it). Usually, Lightstages are used for facial feature capture, but I’m kinda interested to use them with plants. With the support of the National Plant Phenomics Centre, here in Aberystwyth, and and Aberystwyth University Research Fund grant (URF) I’ve been slowly putting one together.

The key ingredient of a Lightstage is a frame which can hold the lights and the cameras equidistant from the target object. We’ve gone for a geodesic dome construction. Here’s a time-lapse video of Geoff from Geodomes.com building ours (a 2 metre 3v dome made out of rigid struts covered in non-reflectant paint). He has a bit of help from Alassane Seck, who did a PhD here in Aberystwyth on Lightstage imaging.

Once we’d got the dome, the next job was to think about mounting lights on the dome. There are a couple of different approaches we can take, but the essential features are that some of the lights are polarised and some of the cameras also have polarising filters. This means we can separate out specular reflections (light that bounces straight off) and diffuse reflections (light that interacts more with the surface of the object). Pete Scully‘s been working on the light placement, doing a lot of work in simulation. Here’s an early simulated placement: dots are lights, boxes are cameras.

The dome was housed in the Physical Sciences building but it’s recently moved. This puts us in a room which is actually light-tight, a key consideration for reducing interference in the controlled lighting situation. Here’s an arty shot of the top of the dome in its new home.

Since the move of room (very recently) things have really picked up. We’ve got a light-proof space, and we’ve got an intern from France (Robin Dousse) working with us too. Andy Starr‘s been working on the electronics and construction from the outset, and during breaks in teaching has really driven the project forwards. Here’s a shot of Robin, Pete and Andy by the dome:

Robin’s been working on programming our LED controllers. We’ve a fairly complicated master-slave controller system, as running 100 or so ultra-bright lights is not trivial. We’re aiming for a pair (one polarised, one not) at each vertex. Here’s a 12 second video of some flashing LEDs. It’s going to look a lot more impressive than this once it’s actually going, but hey, this is actual lights lighting up on our actual dome so I am very pleased.

We’ve now also, finally, got cameras on the dome. We’re not 100% certain about positioning, but we’re getting there. Andy’s been working on the camera triggers. Soon we’ll have something which flashes, takes pictures, and gives us the data we want.

shadows of interest #1

I’ve decided to start a new blog series – one of my research interests is shadows, and so I have been accruing a collection of strange and interesting shadow images. Here is #1.

I don’t know where the image comes from but will happily add an attribution if anyone can find out…