[oscilloscope]

It's possible your device has older hardware. I have one from several weeks ago. It does indeed get 120+ fps even with the JavaScript API. Fingers do drop, but I notice that problem less in "precise" mode which is closer to 60 fps.

The JavaScript API doesn't do much for you, but the data is still quite good coming over the WebSocket. I've used it to create some galleries of gestures, and a gesture diagnostic tool. I've been trying to come up with solutions to the problems you've described... if it starts working out I'll release a 3rd-party JavaScript library for better finger permanence and filtering out noisy data.

http://fleetinbeing.net/leap-play/recorder-gallery.html

http://fleetinbeing.net/leap-play/recorder-diagnostic.html

[oscilloscope]

Updating to this post: I was able to test on newer Leap hardware and fingers no longer drop or jitter. I don't think a JavaScript library will be necessary to filter noise or track fingers in the production version.

[hamxiaoz]

That looks awesome! I'm just learning d3 and I didn't notice d3 can do so many cool stuff.

[oscilloscope]

You can skip data-binding, the update pattern and SVG for this kind of step-by-step animation. I use Canvas to render these and just a few d3 functions (scales, extents, json). Here's another example to learn from that uses similar techniques to get good performance out of Canvas:

http://www.jasondavies.com/maps/transition/