simulate_2_ex_3_kelly

int numSprings = 3;

Spring2D[] s = new Spring2D[numSprings];

float gravity = 5.0;

float mass = 3.0;

​

void setup() {

  size(500, 500);

  for (int i = 0; i < numSprings; i++) {

    s[i] = new Spring2D(width/2, i*(height/numSprings), mass, gravity);

  }

}

​

void draw() {

  background(20,160,180);

  fill(255,180,0,200);

  s[0].update(mouseX*4, mouseY*4);

  s[0].display(mouseX*1.5, mouseY*1.5);

  for (int i = 1; i < numSprings; i++) {

    s[i].update(s[i-1].x, s[i-1].y);

    s[i].display(s[i-1].x, s[i-1].y);

  }

  fill(10,200,50,100);

    ellipse(80,70, 125,125);

  fill(20,160,180);

  beginShape();

    vertex(80,70);

    vertex(150,60);

    vertex(150,15);

  endShape(CLOSE);

  pushMatrix();

  translate(350,300);

  rotate(HALF_PI);

  scale(1.5);

  fill(10,200,50,150);

    ellipse(80,70, 125,125);

  fill(20,160,180);

  beginShape();

    vertex(80,70);

    vertex(150,60);

    vertex(150,15);

  endShape(CLOSE);

  popMatrix();

  pushMatrix();

  translate(450,150);

  rotate(PI/1.3);

  scale(0.7);

  fill(10,200,50,100);

    ellipse(80,70, 125,125);

  fill(20,160,180);

  beginShape();

    vertex(80,70);

    vertex(150,60);

    vertex(150,15);

  endShape(CLOSE);

  popMatrix();

}

class Spring2D {

  float vx, vy; // The x- and y-axis velocities

  float x, y; // The x- and y-coordinates

  float gravity;

  float mass;

  float radius = 10;

  float stiffness = 0.2;

  float damping = 0.7;

  int shrink = 0;

​

  Spring2D(float xpos, float ypos, float m, float g) {

    x = xpos;

    y = ypos;

    mass = m;

    gravity = g;

  }

​

  void update(float targetX, float targetY) {

    float forceX = (targetX - x) * stiffness;

    float ax = forceX / mass;

    vx = damping * (vx + ax);

    x += vx;

    float forceY = (targetY - y) * stiffness;

    forceY += gravity;

    float ay = forceY / mass;

    vy = damping * (vy + ay);

    y += vy;

    shrink -= 13;

  }

​

  void display(float nx, float ny) {

    noStroke();

    ellipse(x/4, y/4, 60, 60);

  }

}

​

​