Category: c

Salutations Interactive Installation: Making of

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Since the post about the Salutations Interactive Installation in the Museum für Kommunikation in Berlin, many people asked me for videos of the installation so we, the Igalia Interactivity team, came up with a better idea — a making of.

The video shows the an early test application that was created from the one shipped with Skeltrack, then some testing with colleagues at Igalia’s office and finally the installation in Berlin and the final result:


(link to original video in YouTube)

You can get the source code for the application from Igalia’s GitHub.

Skeltrack 0.1.8 released

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Skeltrack, the Open Source library for skeleton tracking, keeps being improved here in Igalia and today we are releasing version 0.1.8.
Since July we have had the valuable extra help of Iago López who is doing an internship in Igalia’s Interactivity Team.

What’s new

Several bug fixes (including the introspection), both in the library and the supplied example were fixed.
The threading model was simplified and the skeleton tracking implementation was divided in several files for a better organized source code.

While the above is nice, the coolest thing about this release (and kudos to Iago for this) is that it makes Skeltrack work better with scenes where the user is not completely alone. The issue was that if there was another person or object (think chairs, tables, etc. for a real life example) was in the scene they would confuse the skeleton tracking. After this version, while not being perfect (objects/people cannot be touching the user), the algorithm will try to discard objects that are not the user.
But what about having two people in a scene, which one will it choose? To control this, we have introduced a new function:

skeltrack_skeleton_set_focus_point (SkeltrackSkeleton *skeleton,
gint x,
gint y,
gint z)

This function will tell Skeltrack to focus on the user closer to this point, thus allowing to focus on a user in real time by constantly changing this point to, for example, the user’s head position.
So, even if there is no multi-user support, the current API makes it easy to just run other instances of Skeltrack and try to pick users from other points in the scene.
It should also be easier to use Skeltrack for a typical installation where there is a user controlling something in a public space while other people are passing or standing by.

Contribute

We will keep betting on this great library.
If you wanna help us, read the docs, check out Skeltrack’s GitHub and send us patches or open issues.

Skeltrack 0.1.4 “smoothie skeleton”

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Here is the new version of Skeltrack, the Free Software library for human skeleton tracking from depth buffers.

Since the last release, I have presented Skeltrack at two events and built a cool demo of what can be done with this library.

What’s new

Apart from some bug fixes, this 0.1.4 version also introduces unit tests for making our development easier.
Yet, the big feature introduced in this version is the joints’ smoothing. If you have tried Skeltrack or watched the videos, you might have noticed that the skeleton is all jittery as if the joints were doing some caribbean dance. This is due to noise and other small changes in the depth buffer that happen in devices like the Kinect (and if you are wondering, it happens to the proprietary alternatives as well), so I implemented a way to smooth the joints’ jitters.

Smooth and quiet

This improvement was implemented using Holt’s Double Exponential Smoothing (which, for example, is what Microsoft’s Kinect SDK uses).
There are two properties that control this feature. The self-explanatory “enable-smoothing” property will turn the smoothing on or off and the “smoothing-factor” determines how much it should be smoothed. This value ranges from 0 to 1 and works as described in the mentioned Holt’s algorithm: values closer to 0 will give more weight to previous values of the joints as opposed to values closer to 1 that will consider the latest and current joints’ values more important. This means that values closer to 0 will offer a better smoothing but a bit of lag might be noticed so users should really choose this value themselves, as there’s no “good for all” factor. The smoothing is enabled by default with a factor of 0.5.

To show how well this might improve your Skeltrack-powered application, here is a video showing Skeltrack with the smoothing disabled and then enabled with a factor of 0.25.


(direct link to video in Vimeo)

The application shown in the video is the Kinect example we ship with Skeltrack which was also updated to allow controlling the smoothing feature.

Contribute

There are still a good number of tasks to be done that will improve Skeltrack. You can contribute too by forking the project at GitHub and sending us patches or you can of course hire Igalia to boost its development and make it rock even harder.

Let me know of any applications you’re developing with Skeltrack and how we can make it better. Check out the documentation and file some bugs if you run into trouble.

Stay smooth.