CODEWITHSUNDEEP
ipad
Bill Drissel
Bill Drissel

Reputation: 186

Is iPad sensitive to the amount of pressure exerted by a finger?

Can I detect the force or pressure exerted by a user (musician's) finger?

Upvotes: 4

Views: 2488

Answers (4)

Rob
Rob

Reputation: 1437

Yes you can detect finger area, which is similar. Really! You just don't get point-pressure which requires a different sensor technology.

You can get a number that's the major radius of your finger in millimeters from every finger individually. It's essentially a processed number related to the number of pixels you are covering with the finger. Unfortunately, I haven't been able to get a straight answer on whether this is a problem to ship this way, so I have to ship with it disabled. But it works. It returns a value from 7.0 to about 11.0, it varies wildly, and you might want to low-pass filter changes to this value.

float vf = 10.0;
id valFloat = [thisTouch valueForKey:"pathMajorRadius"];
if(valFloat != nil)
{
  vf = [valFloat floatValue];
}

As an iPad developer, it drives me COMPLETELY insane that this has worked since the iPad shipped, works now in iOS4.2, and still doesn't appear to be sanctioned. This feature is a basic requirement for many classes of application if you want something that's more than a $2 toy.

Upvotes: 2

picciano
picciano

Reputation: 22711

Done. See my answer in Tap pressure strength detection using accelerometer

Upvotes: 0

Tim
Tim

Reputation: 8919

You cannot detect pressure but you can detect velocity of movement (distance/time) and you could establish a linear relationship between velocity and force -> volume. You could make a bell ring louder, for example, by swiping your finger vigorously, rapidly across the bell, and quietly by a gentle, short, slow stroke. Probably would work OK with harp strings.

Upvotes: 1

Juho Vepsäläinen
Juho Vepsäläinen

Reputation: 26873

Not yet.

There's a technical demo showing how to do it. See http://tenonedesign.com/blog/pressure-sensitive-drawing-on-ipad/ . Hopefully something comes out of that. :)

Upvotes: 3

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