can i use if statements to change a float value if certain conditions are met?

rossdickinson

Hey, I am wanting to edit my sketch so that the attraction of the nodes is disabled when there is no hand detected by kinect. So the attraction would start with a force of 0, but turn to 1 when the wave gesture had been completed and a hand was being tracked, then it would become 0 again onLostHand. A way I thought this would be possible would be to add if statements to the kinect related void's near the end of the sketch, but i'm unsure about how to do that.

I am still a processing baby so any help would be super appreciated even if it's just to tell me it won't work. Thank you!!!

Windows 8 Processing 2.1.2

page1

class Attractor {
  // position
  float x=0, y=0;

  // radius of impact
  float radius = 500;
  // strength: positive for attraction, negative for repulsion
  float strength = 1; 
  // parameter that influences the form of the function
  float ramp = 0.5;    //// 0.01 - 0.99


  Attractor(float theX, float theY) {
    x = theX;
    y = theY;
  }


  void attract(Node theNode) {
    // calculate distance
    float dx = x - theNode.x;
    float dy = y - theNode.y;
    float d = mag(dx, dy);

    if (d > 0 && d < radius) {
      // calculate force
      float s = pow(d / radius, 1 / ramp);
      float f = s * 9 * 1 * (1 / (s + 1) + ((s - 3) / 4)) / d;

      // apply force to node velocity
      theNode.velocity.x += dx * f * 3;
      theNode.velocity.y += dy * f * 3;
    }
  }

}

code page 2

//gravity
import generativedesign.*;

//kinect
import java.util.Map;
import java.util.Iterator;

import SimpleOpenNI.*;

// gravity
int xCount = 70;
int yCount = 70;
float gridSize = 600; 

Node[] myNodes = new Node[xCount*yCount];
Attractor myAttractor; 

// kinect
SimpleOpenNI context;
int handVecListSize = 20;
Map<Integer,ArrayList<PVector>>  handPathList = new HashMap<Integer,ArrayList<PVector>>();
color[]       userClr = new color[]{ color(255,0,0),
                                     color(0,255,0),
                                     color(0,0,255),
                                     color(255,255,0),
                                     color(255,0,255),
                                     color(0,255,255)
                                   };


 void setup() { 
  size(600,600);
  background(230);
  smooth();
  noStroke();
  fill(0);

  //kinect
    context = new SimpleOpenNI(this);
  if(context.isInit() == false)
  {
     println("Can't init SimpleOpenNI, maybe the camera is not connected!"); 
     exit();
     return;  
  }  
  context.enableDepth();
  context.setMirror(true);
  context.enableHand();
  context.startGesture(SimpleOpenNI.GESTURE_WAVE);

  //gravity

  initGrid();

  myAttractor = new Attractor(0, 0);
  myAttractor.strength = -3;
  myAttractor.ramp = 2;
}

void draw() {

  background(230);

  //kinect

  context.update();

  Iterator itr = handPathList.entrySet().iterator();
  while(itr.hasNext())
  {
  Map.Entry mapEntry = (Map.Entry)itr.next();
  int handId = (Integer)mapEntry.getKey();
  ArrayList<PVector> vecList = (ArrayList<PVector>)mapEntry.getValue();
  PVector p;
  PVector p2d = new PVector();
  Iterator itrVec = vecList.iterator();
  p = (PVector) itrVec.next();
  context.convertRealWorldToProjective(p,p2d);

  //gravity
   myAttractor.x = p2d.x;
  myAttractor.y = p2d.y;

   //kinect
   p = vecList.get(0);
   context.convertRealWorldToProjective(p,p2d);
   //point(p2d.x,p2d.y);
  }
    //gravity
  for (int i = 0; i < myNodes.length; i++) {
      myAttractor.attract(myNodes[i]);
     myNodes[i].update();
       rect(myNodes[i].x, myNodes[i].y, 2, 2);
}
}

void initGrid() {
  int i = 0;
  for (int y = 0; y < yCount; y++) {
    for (int x = 0; x < xCount; x++) {
      float xPos = x*(gridSize/(xCount-1))+(width-gridSize)/2;
      float yPos = y*(gridSize/(yCount-1))+(height-gridSize)/2;
      myNodes[i] = new Node(xPos, yPos);
      myNodes[i].setBoundary(0, 0, width, height);
      myNodes[i].setDamping(0.8);  //// 0.0 - 1.0
      i++;
    }
  }
}


void keyPressed() {
  if (key=='r' || key=='R') {
    initGrid();
    background(230);
  }
}

void onNewHand(SimpleOpenNI curContext,int handId,PVector pos)
{
  println("onNewHand - handId: " + handId + ", pos: " + pos);

  ArrayList<PVector> vecList = new ArrayList<PVector>();
  vecList.add(pos);

  handPathList.put(handId,vecList);
}

void onTrackedHand(SimpleOpenNI curContext,int handId,PVector pos)
{
  //println("onTrackedHand - handId: " + handId + ", pos: " + pos );

  ArrayList<PVector> vecList = handPathList.get(handId);
  if(vecList != null)
  {
    vecList.add(0,pos);
        if(vecList.size() >= handVecListSize)
      // remove the last point 
      vecList.remove(vecList.size()-1); 
  }  
}

void onLostHand(SimpleOpenNI curContext,int handId)
{
  println("onLostHand - handId: " + handId);
  handPathList.remove(handId);
}

// -----------------------------------------------------------------
// gesture events

void onCompletedGesture(SimpleOpenNI curContext,int gestureType, PVector pos)
{
  println("onCompletedGesture - gestureType: " + gestureType + ", pos: " + pos);

  int handId = context.startTrackingHand(pos);
  println("hand stracked: " + handId);
}

quark

If I understand the problem correctly there is no need for if statements.

Create a global variable at line 11

float attrForce = 0;

then in the onLostHand method add the statement

attrForce = 0;

then in the onCompletedGesture method add the statement

attrForce = 1;

rossdickinson

Hi @quark, thanks so much for the speedy reply! Not entirely sure what you mean here, any chance you would potentially be able to write your alterations into the initial code? thank you for your help!

rossdickinson

oop! spoke to soon managed to get it working after all. Thanks so much for your help :)

quark

In your formula the * 1 is doing nothing (because x = 1 * x for all x), but you could use this for 'scaling' f e.g.

float f = s * 10 * (1 / (s + 1) + ((s - 3) / 4)) / d;

scales the force by a factor of 10. Try changing the scaleing value 10 to get the desired effect.

quark

@rossdickinson

Please do not delete from existing comments. My last comment was in reply to a question you posted but no longer exists. Answers are not much use without the question.

rossdickinson

Oh sorry, my original reply said that the changes i made worked but they hadn't so didn't want to close off the communication when it was still busted. I will just add edits in the future. thanks again!