[LoSboccacc]

and to think there was an api to derive pressure from contact size back in 2.0

https://developer.apple.com/library/ios/documentation/UIKit/...

anyone knows any app usage of this? I remember some games had pressure calculated from the accelerometer, don't know if any did use this one instead.

[Synaesthesia]

GarageBand also uses accelerometer data to try get the velocity of taps on drums it works reasonably well, not like 3D Touch of course.

[gdubs]

That was a private API -- not sure what Apple used it for, since GarageBand was using accelerometer from what I could tell.

[eridius]

In iOS 8 it became a public API. But the problem is that this didn't actually directly measure pressure, it just measured touch radius. Pressure affects touch radius, but so do a lot of other things (finger size, what part of the finger is used, which finger is used, etc) and so it's not particularly effective at extracting pressure.

[sigmar]

I would love to see how closely/consistently the output from "contact size" increases with "force"

[_rknLA]

This sort of thing really depends on the application, and the nice feature provided with the new "force" property is that you can actually distinguish between a "whole finger pad" light touch, and a "thin, firm, almost just the finger nail" hard touch, and most things in betwee.

[LoSboccacc]

I don't think is gonna be consistent among different fingers/people, sadly. but synaptic did pressure sensitivity on contact area long ago, wouldn't be surprised if they got some nice normalization heuristic already going.

edit this is funny coincidence: the dev guide for synaptic says 255 level but better badn in 7 levels at most

(2005) http://arstechnica.com/civis/viewtopic.php?f=9&t=352584

Edit: I know those are not really comparable teches, force touch for one is transparent