p1222a_2012_cinderTutorialCh5Rewrite

class Particle{

  PVector loc;

  PVector vel;

  PVector acc;

  float mass;

  float decay;

  float r;

  float rDest;

  Particle(PVector initLoc, PVector initVel){

    loc = initLoc;

    vel = initVel;

    acc = new PVector(0,0);

    decay = random(0.9,0.95);

    rDest = 5;

    r = 3;

    mass = sq(r)*0.0001+0.01;

  }

  void update(PImage pattern){

    vel.add(acc);

    float maxVel = r+0.0025;

    float velLength = sq(vel.mag())+0.1;

    if(velLength>sq(maxVel)){

      vel.normalize();

      vel.mult(maxVel);

    }

    loc.add(vel);

    vel.mult(decay);

    acc.set(0,0,0);

    if(loc.x>0 && loc.x<width-1 && loc.y>0 && loc.y<height-1){

      int index = floor(loc.x) + floor(loc.y)*pattern.width;

      rDest = brightness(pattern.pixels[index])/float(255)*3+0.5;

    }else{

      rDest = 0.1;

    }

    r = lerp(r,rDest,0.1);

    mass = sq(r)*0.0001+0.01;

  }

  void display(){

    strokeWeight(r*2);

    point(loc.x,loc.y);

  }

}

​