====== Toile mobile ======

Solution du TD [[nsi:tds:animation:toile_mobile|Toile mobile]]

<code java>
final int N = 100;
final float d = 10;
final float k = 0.01;
final float Rmax = 50;
final float mu = 0.9999;

Node[] nodes = new Node[N];

void setup() {
  size(800, 600);
  fill(255);
  stroke(255);
  for (int i=0; i<N; i++) {
    float x0 = random(width);
    float y0 = random(height);
    nodes[i] = new Node(x0, y0);
  }
}

void draw() {
  background(100,100,200);
  for (int i=0; i<N; i++) {
      for (int j=i+1; j<N; j++) {
          nodes[i].acceleration(nodes[j]);
      }
  }
  for (int i=0; i<N; i++) {
      nodes[i].update();
      nodes[i].display();
  }
  for (int i=0; i<N; i++) {
      for (int j=i+1; j<N; j++) {
          nodes[i].drawLine(nodes[j]);
      }
  }
}

class Node {
  float x, y, vx, vy;
  
  Node(float x0, float y0) {
    vx = 0;
    vy = 0;
    x = x0;
    y = y0;
  }
  
  void update() {
      x += vx;
      y += vy;
      vx *= mu;
      vy *= mu;
      if (y > height) {
        y = 2*height - y;
        vy = -vy;
      } else if (y< 0) {
        y = -y;
        vy = - vy;
      }
      if (x > width) {
        x = 2*width - x;
        vx = -vx;
      } else if (x< 0) {
        x = -x;
        vx = - vx;
      }
  }
  
  void acceleration(Node n) {
    // modifie vx et vy selon les particules proches
    float dist2 = (x-n.x)*(x-n.x) + (y - n.y)*(y - n.y);
    if (dist2 > Rmax*Rmax) {
        return;
    }
    float dvx = (n.x - x) * k;
    float dvy = (n.y - y) * k;
    vx += dvx;
    vy += dvy;
    n.vx -= dvx;
    n.vy -= dvy;
    
  }
  
  void drawLine(Node n) {
    float dist2 = (x-n.x)*(x-n.x) + (y - n.y)*(y - n.y);
    if (dist2 < Rmax*Rmax) {
        line(x, y, n.x, n.y);
    }
  }
  
  void display() {
    circle(x, y, d);
  }
}
</code>