public void draw(Graphics g) {
animate();
g.setColor(Color.black);
g.fillRect(0, 0, dim.width, dim.height);
g.setColor(Color.white);
numpaint++;
DebugPrinter dbg = new DebugPrinter(g, 50, 60);
dbg.print(
"Spring-mass demo by yigal irani, drag balls or create new ones by clicking inside box");
dbg.print("frame", numpaint);
dbg.print("fps", 1 / timer.time_diff);
Point top_left = point_by_vec(new Vec(-1, 1));
g.draw3DRect(top_left.x, top_left.y, screen_dist(2), screen_dist(2), true);
for (int i = 0; i < springs.size(); i++) {
Spring spring = springs.get2(i);
Point p1 = point_by_vec(balls.get2(spring.start).pos);
Point p2 = point_by_vec(balls.get2(spring.end).pos);
g.drawLine(p1.x, p1.y, p2.x, p2.y);
}
for (int i = 0; i < balls.size(); i++) {
Ball ball = balls.get2(i);
Point p = point_by_vec(ball.pos);
int screen_radius = screen_dist(RADIUS);
g.setColor(Color.blue);
g.fillOval(p.x - screen_radius, p.y - screen_radius, screen_radius * 2, screen_radius * 2);
g.setColor(Color.white);
g.drawOval(p.x - screen_radius, p.y - screen_radius, screen_radius * 2, screen_radius * 2);
g.drawString("" + i, p.x, p.y);
}
}
void the_derive(double time, double y[], double dy[]) {
int i;
BallVector balls = decode_balls(y); // new BallVector();//Ball[num_balls];
BallVector dballs = new BallVector(); // new Ball[num_balls];
for (i = 0; i < num_balls; i++) {
Ball p = balls.get2(i);
Ball d = new Ball();
d.pos = p.speed;
d.speed = wall_power(p);
d.speed.y -= 1; // gravity
dballs.add(d);
}
for (i = 0; i < num_balls; i++)
for (int j = i + 1; j < num_balls; j++) {
Ball p1 = balls.get2(i);
Ball p2 = balls.get2(j);
if (far_away_fast_calc(p1.pos, p2.pos, radius * 2)) continue;
double dist = p1.pos.calc_dist(p2.pos);
// if (dist>radius*2)
// continue;
Vec collide_power = calc_collide_power(p1, p2, dist);
dballs.get2(i).speed.add_to(collide_power);
dballs.get2(j).speed.sub_to(collide_power);
}
for (i = 0; i < springs.size(); i++) {
Spring s = springs.get2(i);
Vec collide_power = calc_spring_power(balls.get2(s.start), balls.get2(s.end));
dballs.get2(s.start).speed.add_to(collide_power);
dballs.get2(s.end).speed.sub_to(collide_power);
}
encode_balls(dballs, dy);
};