I'm developing a game in which player can use ropes to swing (just like what Spiderman or Bionic Commando did) and I'm having problem implementing this behavior. Can anyone help me how to do this, I mean physics formulas and etc. Till now I've come up with 3 ideas. One is using spring, but it consumes a lot of time and sometimes it is jumpy. The other two are trying to calculate next step (one via calculating potential energy and one via calculating torque) and both of them almost crash whenever the actor is trying to swing.
Here is the code I wrote to calculate torque:
float dx = Runner->getPosition().x - ancher.x; float dy = Runner->getPosition().y - ancher.y; float t0 = atan2(dy,dx); //my current angle float k = ((dy) *vx - (dx) * vy) / (dx * dx+dy * dy); //previus angular velocity k -= gravity * cos(t0) *dt; // new angular velocity (gravity is positive) t0 += k * dt - acc * cos(t0) *dt * dt / 2; // rotate the rope float dx1 = r0 * cos(t0); // new position (r0 is rope length) float dy1 = r0 * sin(t0); vx = (dx1 - dx) / dt; //calculate velocity vy = (dy1 - dy) / dt;