Question

Im making a 2D game where the player controls a tank.

I can make the tank, and all, but whats really messing with my mind is how to make it rotate accordingly.

I want it to behave just like the Wii game, Tanks.
Fixed directions, and with no real front and back on the tank.

Driving up, then left should make it rotate to the left.
Driving up, then down should not make it rotate, just drive the other direction.

I red a tutorial a while back about some way to do that by dividing the degrees into 2 180 degree parts. But i have simply not been able to find that damn site again.

I hope you guys are able to understand what im trying to say.
Thanks in advance 🙂

Answer 1

I think what you’re looking for is simply the best way to minimize the rotation of the tank, modulo 180 degrees.

I would use the angle between the desired movement direction and the tank’s current direction to start. Make sure this is the minimum angle, then compare that with the angle between the tank’s current direction + 180 degrees. Something like:

// smallest angle between the current direction and the desired direction
minAngle1 = Math.Abs(Math.Min(tankAngle - desiredAngle, desiredAngle - tankAngle));

// smallest angle between the opposite direction and the desired direction
oppositeAngle = (tankAngle + 180) % 360;
minAngle2 = Math.Abs(Math.Min(oppositeAngle - desiredAngle, desiredAngle - oppositeAngle));

// get the smaller of two to rotate to
if (minAngle1 < minAngle2)  {
  // we know that we should rotate the current direction to the desired direction
} else {
  // rotate the opposing direction to the desired direction
}

Note you’ll need to play with your rotation signs to ensure you’re rotating the right way. Also, I’ve assumed you know your rotation angles, if you have vectors you can simplify this a little bit by using the dot product between the two vectors instead of the angle for comparisons.