Creating my own gesture

[Cla22ire]

Hi everyone ,
I'm devolping an app ( in C# using unity ) that needs a diffrent gesture from the ones provided
The gesture I want to create is the user will tap the screen for an amount of time and then something will happen , it's almost like the screen tap
here an image that explain it: http://i57.tinypic.com/2poprnt.jpg
the issue is that I don't know how to begin at all , help me
Thanks ~

[Komposten]

This is a method I use for that kind of effect (if I understand you correctly). Just beware that I'm not a particularly experienced programmer, so there might be better ways of doing this.

Every frame you can check if the finger is past a certain z-value (depth) and if it is, you add the time that has passed since the last frame to a variable. Then check if the time variable exceeds your desired waiting time.

Here's some basic code (I'm writing using Java, but it shouldn't be that different):

void update()
{
  if (finger.getZ() > threshold) //Check if finger is past the threshold
  {
    timeTapped += timeSinceLastUpdate; //Add time to the time variable
  }
  else
    timeTapped = 0; //If the finger isn't past the threshold, reset the time

  if (timeTapped > TAP_DURATION) //If the finger has been held for the right amount of time, do something.
    print("Tapped!");
}

I hope you understand what I mean and that it can get you started.

//Komposten

[dplemmons_leap]

@Komposten Yep, that's exactly how to do it! I'd add one thing which is to not let a new event fire until the user has pulled their hand back up.

So you need a bool to track the current "armed" state and have a check to re-art the button.

private bool tapArmed = false;

void update()
{
  if (finger.getZ() > threshold) //Check if finger is past the threshold
  {
    timeTapped += timeSinceLastUpdate; //Add time to the time variable
  }
  else
    tapArmed = true; //Arm the menu for another attempt if not already.
    timeTapped = 0; //If the finger isn't past the threshold, reset the time

  if (timeTapped > TAP_DURATION && tapArmed) //If the finger has been held for the right amount of time, do something.
    print("Tapped!");
    tapArmed = false;
}

I wrote this in the forum directly so code is untested.

[Komposten]

@dplemmons_leap You'd missed a couple of curly braces around the 'if's:

private bool tapArmed = false;

void update()
{
  if (finger.getZ() > threshold) //Check if finger is past the threshold
  {
    timeTapped += timeSinceLastUpdate; //Add time to the time variable
  }
  else
  {
    tapArmed = true; //Arm the menu for another attempt if not already.
    timeTapped = 0; //If the finger isn't past the threshold, reset the time
  }

  if (timeTapped > TAP_DURATION && tapArmed) //If the finger has been held for the right amount of time, do something.
  {
    print("Tapped!");
    tapArmed = false; //Set tapArmed to false to prevent the event to be sent every frame until the finger is withdrawn.
  }
}

[dplemmons_leap]

Whoops! Good catch. I've been writing a lot of python of late (no brackets), too much context switching!

[lm_dedelhart]

A few thoughts. This is good for any language.

The gestures we have included are not the last word in motion capture. Any app with leap is going to require you to do your own motion qualification.

A few things to keep in mind:

• Fingers -- that is a record in the frame data set with a particular ID -- are prone to disappear as the scanner unrecognizes/recongnizes them.
• You have to be careful to discriminate between motions that the user is likely to do to navigate and those they are doing to select/activate. IN a sense you have to detect the "not gesture state" as well as the gesture state.
• Using directional vectors is useful. both the direction the finger is pointing and the direction the finger is moving. I've found it is useful to average (with noise suppression) the fingers' position over the last 6 or so frames and use it to make your own finger motion vector to calculate the motion of the finger. Comparing that to the orientation vector of the finger can determine whether it is poking straight or sweeping to the side.
• Using the frontmost few fingers is a good way to filter out the thumb and pinkies.
• Provide a visual cue in the form of a cursor as the user generates a gesture to let them "balk out" of a gesture they don't want.
• Provide a cool-down time to avoid inadvertently "Double Gesturing". This should include the time it takes to execute whatever effect you want the gesture to make.
• Make sure to lock the focus of your gesture down when it has started to a single finger. That is you don't want to have "start-poke: F1 .... Start-poke: F2 ... end-poke: F1 .. end-poke: F2" and generate two machine-gun gestures .
• Avoid filtering gestures by z-position; its pretty difficult for users to really know how "deep" their hands are. relative Z-motion is fine, but absolute position is not a great hook.
• Limit gesture starts to well within the detection zone; you don't want them "brushing out" of range mid gesture.
• Detecting when fingers touch each other (pinch) is a bad route, as detecting fingerness of a closed finger loop is problematic at this point. You can detect a pinch, but make sure that you end the gesture while the fingers aren't quite touching.

[Cla22ire]

@Komposten @dplemmons_leap
I'm very gratefull for your posts here ! I love you guys , you are the best !!
Now I can really start working ~ Thank you very much

@lm_dedelhart thanks for the advices , I'll keep it mind

[AlexColgan]

@lm_dedelhart's response is so nice, we decided to steal, er, borrow it. Yes, borrow.

Anyway, it's now a Knowledge Base article so that all Leap Motion devs can easily find and access it: https://leapmotion.zendesk.com/entries/41213338-Tips-for-Building-Gestures-Into-Applications

[LastBlow]

@AlexColgan The page it linkes to doesn't exist anymore. Would you, please, update the link? Also, now that gestures are deprecated, examples/tutorials on how to define a gesture would be REALLY appreciated with the new API. Hope to hear back from you soon, thanks.

[AlexColgan]

It was removed because Gestures have been deprecated; the original insights remain in @lm_dedelhart's post. If you're developing with Unity, I recommend checking out the Detectors Examples, which cover pose-based gestures.

[umeer]

What would be the equivalent for Unreal Engine in regards to examples?

[AlexColgan]

There is no functional equivalent in the Unreal integration, though the rules for hand poses in the Detectors Examples can be rewritten for C++.