Sunday, 12 January 2014

Motion Capture comes to Bucks

The "T pose"
Last week Motion Capture came to Bucks New University for the first time. The green screen room in the Gateway building played host to our latest, biggest and most expensive digital toy, extremely useful not just for animators hoping to capture excellent physical performances but also for students studying sports and motion analysis, helping to turn physical performances and actions into data that can be analysed, broken down, and used to improve the performance of athletes. It's cutting edge stuff, and it's happening right here at Bucks.

Our visitor and teacher was Jeff Shaw from Motion Analysis, one of the global leaders in MoCap technology. He came to Bucks for a week to set up the gear and instruct our “Power Users” in the new technology.

Raptor 4 cameras
The heart of the system is ten "Raptor 4" real time cameras, of four megapixels each, which were lined up in two rows of five on either side of the green screen room. The process of setting them up involves two stages - the setup, followed by camera calibration. The Green Screen room then becomes the Motion Capture stage on which pretty much any action or performance you can think can be acted out.

Jeff Shaw shows how it's done.
The Software used to create the data is called Cortex, and it is installed on the HP Z240 desktop PC used for the Green Screen Room. All the equipment is hosted at Media Resources, so it will need to be booked in advance and then checked out for use.

Motion Capture Marker
Everyone has heard of motion capture suits, but it turns out that this is something of a misnomer. The suit itself does not matter – it’s the markers that are important. The main characteristic of a good suit is that the markers sit close to the joints. So, a cheap leotard works well, or a tight fitting T shirt and jeans. Anything that hugs the body, so the markers don't float around.

It is also important to attach the markers correctly. Luckily, Cortex provides you with a checklist of the 42 markers that (generally speaking) go into capturing a piece of human biped animation.  In the image below you can see four markers being attached to the performer's feet, to get a full range of motion. The markers go on either side of the joint; in this case, the ankle.

Markers must go in the right place,

This is the critical bit, especially for sports bio motion analysis. It is less critical for animation, but still important to get right.  They need to be properly attached - you have to watch out for markers falling off shoes and other body parts.

For the motion capture hat (you need data on what the head is doing), Jeff used an inexpensive yellow hard hat, and attached the markers to it. In fact, you need quite a bit of kit to get underway. Luckily we now have the complete bag of tricks to get started.

Kitbag full of MoCap stuff.
None of it is cheap - even markers cost several pounds each, so they need to be treated with care.  We also have double sided sticky pads to attach the markers to clothing. It turns out you can also use toupee tape, available at Boots.

As for shoes, you will want inexpensive plimsoles or trainers, nothing that you might mind getting beaten up or damaged.

Anyone wanting to fire up the equipment will also need the dongle, which pops into the USB port in the back of the PC, and activates the Cortex license.  Plus, of course, you need to set up the ten Raptor cameras. It is not a quick process - you must allow a couple of hours at least for setup, and then time to take it all down again.

In fact, I counted ten distinct stages to the whole motion capture process, from setup to animator's desk:

1. Setup – cameras and equipment
2. Calibration of the cameras
3. Placing the markers on the performer
4. Capturing the performance data
5. Processing the data in Cortex
6. Cleaning up the data in Cortex
7. Exporting the data from Cortex into Motion Builder
8. Editing the motion capture data in Motion Builder, then exporting it to Maya
9. Importing the motion capture data into Maya
10.Taking down the equipment and returning it to Media Resources.

That said, MoCap has the potential to revolutionise animation at Bucks. It's a system that can capture large amounts of data and process it much faster than a key frame animator can. It is used for games, for TV shows, for feature animation. To understand this pipeline is to have a whole new set of skills that are highly desirable in today's competitive job market.

Over the coming weeks and months we'll be figuring how to incorporate this new system into our existing curriculum, so that we can give our students the best possible experience at Bucks, and get to grips with the very latest digital technology.

(Editor's Note: for more on how our students are working with motion capture technology, check out our trip to Pinewood Studios last year.)

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