@fladdict さんの 「JSでアメーバのシミュレーション作ってみた」 http://fladdict.net/blog/2013/04/js-ameba.html のjavascriptソースコードをProcessing及びProcessing.jsで動くように修正してみた。動くように修正しただけなので、リファクタリングもかけてないですし、中のコメントも残したまんまです。

Ameba.pde

int numberOfNodes = 200;
Node[] nodes = new Node[numberOfNodes];
int pressedCount = 0;
float pressedX;
float pressedY;
//var calcTable;
float lineAlpha = 0;

void setup() {
  size(displayWidth, displayHeight); //Processing 2.x以降はdisplayWidth
	//size(screenWidth, screenHeight); //if Processing 1.5.1まではscreenWidth
	background(0, 0, 0);
	//For FullScreen
	//@//HTMLのためのコードなので無視
	//@  window.onresize = function()
	//@  {
	//@    size(window.innerWidth,window.innerHeight);
	//@  };
	
  setup2();
}

void setup2() {
	for (int i=0; i<numberOfNodes; i++) {
		Node nd = new Node();
		nd.x = random(1f) * width;
		nd.y = random(1f) * height;
		nd.nodes = nodes;
		nd.nodeType = int(random(1f)*2);
		nodes[i]= nd;
	};

	//@高速化テーブル  [NodeXId][NodeYId][dx,dy,dist];
	//@あとで採用して最適化すること
	//@	calcTable = [];
	//@	for(var yy=0; i<numberOfNodes; yy++){
	//@		var ar = [];
	//@		for(var xx=0; j<numberOfNodes; xx++){
	//@			ar.push([0,0,0]);
	//@		}
	//@	calcTable.push(ar);
	//@	}
}

void draw() {
	colorMode(RGB, 255);
	fill(0);
	noStroke();
	rect(0, 0, width, height);

	int  n = nodes.length;
	if (pressedCount>0) {
		pressedCount--;

		for (int i=0; i<n; i++) {
			Node nd = nodes[i];
			nd.maxVelocity=3;
			nd.friction = 0.99;
			nd.updateVelocity();
			nd.updatePosition();
		}
	}else {
		lineAlpha = lineAlpha + (1-lineAlpha)*0.01;
		for (int i=0; i<n; i++) {
			Node nd = nodes[i];
			nd.maxVelocity=1;
			nd.friction = 0.9;
			nd.resetForce();
			nd.update();
		}
	}


  for (int i=0; i<n; i++)
  {
    for (int j=i; j<n; j++)
    {
      Node nd0 = nodes[i];
      Node nd1 = nodes[j];
      if (nd0!=nd1) {
        float dx = nd1.x - nd0.x;
        float dy = nd1.y - nd0.y;
        float dist = sqrt(dx*dx+dy*dy);
        if (dist<150 && dist!=0 && nd0.nodeType==nd1.nodeType) {
          //255で0、 100で1
          // (255-dist);
          float strokeCol = (150-dist)*1.5;
          stroke(strokeCol * lineAlpha);
          line(nd0.x, nd0.y, nd1.x, nd1.y);
        }
      }
    }
  }

  for (int i=0; i<n; i++) {
    Node nd = nodes[i];
    nd.draw();
  };
}

void mousePressed()
{
	pressedCount = 120;
	pressedX = mouseX;
	pressedY = mouseY;
	lineAlpha = 0;

  int n = nodes.length;
  for (int i=0; i<n; i++) {
    Node nd = nodes[i];
    float fx = nd.x - mouseX;
    float fy = nd.y - mouseY;
    float dist = sqrt(fy*fy+fx*fx);
    float rad = atan2(fy, fx);
    if (dist>1) {
      nd.fx += cos(rad)/dist*800;
      nd.fy += sin(rad)/dist*800;
      nd.updateVelocity();
      nd.updatePosition();
    }
  };
}


class Node {
	float x =0;
	float y = 0;
	float vx = 0;
	float vy = 0;
	int maxVelocity = 2;
	float fx = 0;
	float fy = 0;
	int nodeType;
	float rotation = 0;
	Node[] nodes;
	float friction = 0.9;

  void init() {
  }

  void update() {
    this.updateBoid();
    this.updateVelocity();
    this.updatePosition();
  }

  void resetForce()
  {
    this.fx = 0;
    this.fy = 0;
  }

  void updateBoid()
  {
    //ここでBoid計算
    int n = this.nodes.length;

    //Calc Position
    int deathCount = 0;
    float fx = 0;
    float fy = 0;

    //仲間に近づく / 離れる
    for (int i=0; i<n; i++) {
      Node nd = this.nodes[i];
      if (nd==this)
        continue;

      float dx = nd.x - this.x;
      float dy = nd.y - this.y;
      float dist = sqrt(dx*dx+dy*dy);
      if (dist<50 && dist>1) {
        deathCount++;
        fx -= dx / dist / dist / dist * 40;
        fy -= dy / dist / dist / dist * 40;
      }
      else if (dist<200 && this.nodeType==nd.nodeType) {
        fx += dx / dist / dist / dist * 30;
        fy += dy / dist / dist / dist * 30;
      }
    }

    //仲間と同じ方向に移動する
    for (int i=0; i<n; i++) {
      Node nd = this.nodes[i];
      if (nd==this)
        continue;

      float dx = nd.x - this.x;
      float dy = nd.y - this.y;
      float dist = sqrt(dx*dx+dy*dy);
      if (dist>1) {
        float vx = nd.vx;
        float vy = nd.vy;
        float rad = atan2(vy, vx);
        fx += cos(rad) /dist/dist;
        fy += sin(rad) /dist/dist;
      }
    }

    //マウスから逃げる
    float mfx = mouseX - this.x;
    float mfy = mouseY - this.y;
    float mdist = sqrt(mfx*mfx+mfy*mfy);
    float mrad = atan2(mfy, mfx);
    //console.log(mdist);
    if (mdist>0) {
      fx -= cos(mrad)/mdist/mdist*300;
      fy -= sin(mrad)/mdist/mdist*300;
    }
    /*
  if(deathCount>20){
     this.x = random()*width;
     this.y = random()*height;
     }*/

    //Normalize Speed
//@//変数distが参照可能なスコープから見当たらない。
//@    float d = dist(fx, fy);
//@    if (d>1) {
//@      fx = fx / dist;
//@      fy = fy / dist;
//@    }

    this.fx += (random(1f)-0.5)*0.2;
    this.fy += (random(1f)-0.5)*0.2;

    this.fx += fx * 3;
    this.fy += fy * 3;
  }

  void updateVelocity()
  {
    this.vx = this.vx * this.friction + this.fx;
    this.vy = this.vy * this.friction + this.fy;

//@//dist(x1,y1,x2,y2)なので動かない。
//@//this.vx / v * this.maxVelocity;が代入などが行われない無効なコード
//@    float v = dist(this.vx, this.vy);
//@    if (v>this.maxVelocity) {
//@      this.vx / v * this.maxVelocity;
//@      this.vy / v * this.maxVelocity;
//@    }
  }

  void updatePosition()
  {
    this.x += this.vx;
    this.y += this.vy;

    if (this.x<0) {
      this.x =0;
      this.vx = abs(this.vx);
      this.fx = 0;
    }
    if (this.x>width) {
      this.x=width;
      this.vx = -abs(this.vx);
      this.fx = 0;
    }

    if (this.y<0) {
      this.y=0;
      this.vy = abs(this.vy);
      this.fy = 0;
    }

    if (this.y>height) {
      this.y=height;
      this.vy = -abs(this.vy);
      this.fy = 0;
    }
  }

  void draw()
  {
    stroke(150);
    ellipse(this.x, this.y, 10, 10);
  }
}