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);
}
}
public BallVector calc_new_frame(
BallVector _balls,
SpringVector _springs,
double _radius,
Timer timer) { // return the the balls of the next frame
balls = _balls;
springs = _springs;
radius = _radius;
num_balls = balls.size();
int i;
for (i = 0; i < NUM_STEPS; i++)
call_rk4(timer.cur_time, timer.time_diff / NUM_STEPS); // too: acum the time?
return balls;
}
int find_ball(Vec v) {
int num_balls = balls.size();
for (int i = 0; i < num_balls; i++) {
Ball p = balls.get2(i);
double dist = v.calc_dist(p.pos);
if (dist < RADIUS) {
// printf("found ball %d\n",i);
find_offset = p.pos.sub(dragged_vec);
// last_dragged_vec=v;
return i;
}
}
return -1;
}
void call_rk4(double cur_time, double time_diff) {
num_balls = balls.size();
double[] y = new_vector(num_balls * 4); // double[num_balls*4];
double[] dy = new_vector(num_balls * 4);
encode_balls(balls, y);
the_derive(
cur_time, y,
dy); // the current implementation of derive does not uses the time, but can envision an
// implementation that might (gravity is off every second, perhaps?)
rk4(y, dy, num_balls * 4, cur_time, time_diff, y);
// balls=new BallVector();
balls = decode_balls(y);
// free_vector(y,1,num_balls*4);
// free_vector(dy,1,num_balls*4);
}
