Frozen Pi: bullet-time photography with the Raspberry Pi

If you were one of the people following us on Twitter a couple of Saturdays ago, when we all hoofed it up to Manchester for the Manchester Raspberry Jam, you’ll have had a sneak preview of this: Dr Andrew “Pi Face” Robinson’s latest Pi escapade. I’ll let Andrew explain what’s going on. (Notice the mildly humiliating guest appearances from me and Clive.)

We think this is one of the most interesting photographic applications we’ve seen in the flesh so far. (Although I will admit to a moment’s disappointment when, on seeing it, getting excited and asking what it did, I was told that it was not a working Stargate after all.) You’ll have read many posts here about bringing down the price of professional photography equipment: we’ve seen focus-stacking on a budget, gigapixel photography, setting up moving time-lapse rigs, and shooting water droplets along with many, many other applications. (The photography tag here is one of my favourites – if you’ve got a few minutes, go and have a read.)

Andrew’s Frozen Pi setup shows us yet another example of bringing photographic technology with an astronomical off-the-shelf price down to achievable levels: of course, with 48 Raspberry Pis this still works out pretty pricey, but it means that any school with a classroom set of Pis suddenly finds it has bullet-time effects photography well within its grasp.

Which is just brilliant, isn’t it? Thanks Andrew!

30 comments

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OH MY GOD
THAT
IS
BRILLIANT!

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That’s very similar to my reaction on the day. (Although it was prefaced by three seconds of “Damn. Not a Stargate.”)

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Interesting the way they used the PiFace. I have a feeling though it could be done without needing those. You would need to write some remote control software which would make all the Pi’s report to a central controller, and that would need to report enough info to allow debugging and stuff.

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The software/display were first set up to run a time-lapse in a field for which the PiFace Control and Displays were needed.

For bullet time, we reused the software and the Pifaces turned out very useful to allow us to see what was was going on when we were setting it up/testing and also to change settings on individual Pis.

The rig is designed so it can be set up in different configurations so we can use the PiFaces to easily change the order of the cameras too.

The blog post has more details http://www.piface.org.uk/iblog

Fully accept they weren’t essential for this set up, but since we had a load of prototypes lying around we thought it would be useful to use them.
We’ve also got plans to turn it into a ring quiz game!

It also meant we could flash the backlights in a cool chase pattern round the ring to make it even more stargate-esque !

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You mean something just like http://www.raspberrypi.org/archives/5232 or http://www.raspberrypi.org/archives/5275 ;-)

All these projects have oodles and oodles of network cables from each Pi, back to a central network switch. I wonder if there’s any way the Pi’s could be connected in a daisy-chain fashion to cut down on the cabling?

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Yes there is. It’s called wireless network…

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LOL. Would using so many Raspis on the same wireless network cause interference or latency issues?

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That’s an interesting idea. Yeah you could probably use the Pi UART for this. Just disable the getty on the serial line in inittab and then you could use jumper wires to connect the TX of Pi 1 to the RX of Pi 2. Then the TX of Pi 2 to the RX of Pi 3 and so on. Only trouble with that though is that it’s a series circuit and if one Pi failed to do its job then that would break the chain.

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The other issue is collection of the frame image files which wouldn’t be easy of they were all wired up in series.

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We wondered about wifi too, but worried if there would be too much contention with 48 near together. Also we went for model B, (so didn’t want to buy extra wifi dongles) as we use those in our workshops with kids — just in case the rig didn’t work!
Having a network is really useful for pushing bug fix software and collecting the images back.

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When we made the Twitter booth wifi was something that caused us reliability issues so the idea of relying on it to communicate reliably with multiple Pis sounds slightly horrifying :)

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I wish i had a classroom full of raspberry pi`s!

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That is so cool… Wow… Just wow…

I saw a picture of it on Twitter the other day and I was rather befuddled: Raspberry Pi CERN was the first thing that came to mind!

The Raspberry Pi Guy

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Well done. You have, unfortunately, a very disappointing result as you use static and balanced objects.

The interest of bullet time is to take an object in motion otherwise you can have the same effect by asking your subjects to not move and rotate a camera around them…

What about, splashing them with water balloon, throw 100 ping pong balls, open the cage of 20 pigeons or 100 butterflies ?

It’s nice; you deserve more spectacular !!!!

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It’s in the plan — we need to get a better support system for the rig (chairs on a wonky floor aren’t great) and then we want to try it with other things.

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Use ply with a 4×2 base. Ask a chippy.

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Andrew, I was thinking you could maybe use something like a Nerf gun being fired… that would show the effect really well. Something like this; http://www.amazon.co.uk/dp/B009NFH54W

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Give the circle a bigger radius and then you can dance about in it.

You too can take on Agent Smith.

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Give the circle a bigger radius and then you can dance about in it.
Scaling up shouldn’t be horrendous in terms of material cost thanks to the circumference (two pi r) scaling linearly with the radius (r). So with twice the radius, you only need twice the number of Pi (machines, not 3.14…). Maybe too obvious to post, but I like how Pi relates to pi in this project :)

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It would also be great to see the effect of the photos taken very slightly apart, say 1/1000 sec. Then you could watch a balloon bursting, a plate smashing, or a water drop landing in a puddle, etc.

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The Pi does make this sort of thing a lot less expensive and a lot more achievable.

One of my projects is a stereo printing system which provides 3D viewing from a flat material (a printed sheet faced by a lenticular screen). To get real as opposed to computer generated artwork for this, from a live subject, would previously have needed a bank of SLRs (say £500 each) and a means of firing them simultaneously (not so easy). So much cheaper and easier on the Pi.

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What about the Pi´s recording video instead of taking photos? Say you record 1 minute of video of the same exact scene but from a slightly different point of view. The with the right piece of software, something like a software video player/switcher one could analize the scene from any angle and forward/rewind it…. you get the idea…

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yeah, we fancied that too but ran out of time. Maybe if we post the files online someone will have a play with some super html5 magicness.

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Does it really need to be a complete circle? I’m sure just a quarter of this would be enough to get the effect.

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You’re right, part of a circle works well too. e.g.
http://www.youtube.com/watch?v=ExE7Ue5Esu8

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Argh, this is like building a color camera, but only show off photos in in black and white. Remove the people and throw things into the rig

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I’m noticing that the white balance and exposure changes throughout the shot. A good suggestion would be to lock these two settings. Otherwise great job!

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It’s absolutely fantastic!

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Hi,

That’s absolutely mind blowing stuff. I was looking for such a tool for months, thanks for sharing the idea and I want to know how and where can I order all the parts needed to make my own bullet time effect? and online tutorials to help me with that?

thanks a lot.

Arvind

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is it possible to trigger DSLR camera with the same set up?

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