Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

arjun.jas..

Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

in Contributed Library Questions • 1 year ago

Hi Everyone

I'm a bit of noob, so bear with me.

I'm trying to make a game where the movement of users hand (as detected by the kinect) moves a ball on the screen. The concept is to have a football game, where the user can direct the ball into both the goals.

My current code detects the hand positions and moves the ball away from the hand using vectors (its almost like someone is kicking the ball away).

The problem is that the ball also reacts to previous hand positions. I find this very strange since, while I am storing all hand positions, I am only using the current position, previous positions are unused. Any help on this would be great!

Thanks in advance!

//for using the kinect

import SimpleOpenNI.*;

SimpleOpenNI kinect;

//storing current hand positions

ArrayList<PVector> handPositions;

PVector currentHand;

PFont f;

PImage b;

Thing t;

void setup() {

size(1000,660);

// for scores

f = loadFont("Serif-48.vlw");

smooth();

// Create the thing object

PVector a = new PVector(0.0,0.0);

PVector v = new PVector(0.0,0.0);

PVector l = new PVector(width/2,height/2);

t = new Thing(a,v,l);

//for background image

b = loadImage("footballfield.jpg");

//innitialize the kinect

kinect = new SimpleOpenNI(this);

kinect.setMirror(true);

kinect.enableDepth();

kinect.enableGesture();

kinect.enableHands();

kinect.addGesture("RaiseHand");

handPositions = new ArrayList();

}

void draw() {

//getting information from the kinect

kinect.update();

//scale(2);

//image(kinect.depthImage(), 0, 0);

background(b);

fill(0);

//player1

ellipse (width/3, height/4, 30, 50);

//player2

ellipse (width/3, 3*height/4, 30, 50);

//player3

ellipse (width/4, height/2, 30, 50);

//player4

ellipse (2*width/3, height/4, 30, 50);

//player5

ellipse (2*width/3, 3*height/4, 30, 50);

//player6

ellipse (3*width/4, height/2, 30, 50);

//acceleration of the ball

float factor;

//start collecting information from the kinect

for (int i = 1; i < handPositions.size(); i++)

{

currentHand = handPositions.get(i);

//draw an ellipse at where the hand is

ellipse(currentHand.x, currentHand.y,20,20);

// Run the Thing object

t.go();

if (dist(currentHand.x, currentHand.y, t.loc.x, t.loc.y) < 60 ) {

// Compute difference vector between handposition and object location

// (1) Get hand Location, (2) Get Difference Vector, (3) Normalize difference vector

PVector m = new PVector(currentHand.x,currentHand.y);

PVector diff = PVector.sub(t.getLoc(),m);

diff.normalize();

/*if hand is on the ball, stop it

if (dist(currentHand.x,currentHand.y, t.loc.x, t.loc.y) < 20 )

{

t.vel.x = 0.0;

t.vel.y = 0.0;

}

factor = 0.005; //acceleration constant

diff.mult(factor);

//object accelerates away from kinect hand position

t.setAcc(diff);

}

else {

t.setAcc(new PVector(0,0));

}

textFont(f, 50);

fill(255);

//display scores

text(t.rgoal,50,100);

text(t.lgoal,width-75,100);

}

Replies(4)

amnon.owed

Re: Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

1 year ago

I am only using the current position, previous positions are unused

No. You have a for loop that goes over all hand positions except the first one.

If you only want to use the last hand position replace this...

for (int i = 1; i < handPositions.size(); i++)
{
currentHand = handPositions.get(i);

...and the corresponding closing brackets by this...

currentHand = handPositions.get(handPositions.size()-1);

arjun.jas..

Re: Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

1 year ago

Thanks for your response Amon.owed, its working now!

I have another issue though:

The canvas size is 1000,660.
However, the depth image from the kinect is much smaller.
As a result, only a part of the canvas responds to the kinect movement.

Is there a way that I could scale the kinect image to the canvas size?

Thanks once again.

amnon.owed

Re: Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

1 year ago

The kinect has a 640x480 canvas.

To resize an image you can use resize(). To rescale the whole sketch you can use scale().

However in this case it's probably simpler to rescale the incoming PVector of the hand positions, before you add it to the arraylist. You can multiply x by (width/640) and multiply y by (height/480). That way the hand position should cover the whole sketch no matter what screen or sketch size you are using.

arjun.jas..

Re: Using Hand Movements to move an circle (Simple OpenNI, Kinect, Vectors)

1 year ago

Thanks again Amnon.owed!

Interestingly:

I tried multiplying the values as they were stored in the arraylist. The function there are all from the Simple OpenNI and each time I messed with them, it would say that the component I was trying to see wasnt visible.
Then I decided to change the values of currentHand.x and currentHand.y when I retrieved them from the array. While this worked, the output had several versions of the hand input ellipse. These scaled as I moved away from the origin. At 0,0 all the versions were close and as I moved away from the kinect canvas space, the space between them increased. Like in the error before, the ball in the centre of the game would also respond to those point.
But, if I change the values of currentHand.x and currentHand.y when I retrieve them and use them to assign two other variables, which I use across the game, the problem doesnt occur.

Not sure, but I think the error in bullet point 2 occurred because I wasnt retrieving things properly.

Am I on the right track with that? Would like to know your opinion.

Otherwise the game is working as expected!

Arjun

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