Show HN: Chordata – The motion capture system that you can build yourself

chordata.cc

16 points·daylankifky··17 comments

Cool project, cheap mocap is a quite an interesting field.

I would have expected a system based purely on such sensors would start to drift and accumulate errors over time. Are there any tricks used to compensate for that?

Thanks! It is not a trick, it's what's called a Sensor fusion algorithm. They come in many flavors, we currently implement Madgwick's one. Another popular and somehow more robust alternatives are Kalman filters, we'll probably also implement one of those in the future.

They all rely on absolute references (gravity and magnetic field) to build a non-drifting reference frame which is used to correct the integration of (angular) accelerations.

Right, totally spaced on that you'd of course get a gravity vector from the sensors too.

The facial mocap system we used for the short thanos scene in the first avengers was an Xbox Kinect and some open source libraries.

So you were on the production of the first avengers movie?

Something like the kinect can be very powerful for facial tracking. But monocular optical techniques tend to give poor body capture results.

Yes.

The tracking data was not used for the final rendering, but was a basis for the animation team to work from.

You can definitely see how much it has improved when comparing that scene to the more recent iterations thanos.

> Xbox Kinect

The Xbox Kinect was such a versatile, and well-built device. Its a shame that its been discontinued and didn't find much use in games.

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