Box2dx: Cancel force on a body?
- by Rosarch
I'm doing pathfinding where I use force to push body to waypoints. However, once they get close enough to the waypoint, I want to cancel out the force. How can I do this? Do I need to maintain separately all the forces I've applied to the body in question?
I'm using Box2dx (C#/XNA).
Here is my attempt, but it doesn't work at all:
internal PathProgressionStatus MoveAlongPath(PositionUpdater posUpdater)
{
Vector2 nextGoal = posUpdater.Goals.Peek();
Vector2 currPos = posUpdater.Model.Body.Position;
float distanceToNextGoal = Vector2.Distance(currPos, nextGoal);
bool isAtGoal = distanceToNextGoal < PROXIMITY_THRESHOLD;
Vector2 forceToApply = new Vector2();
double angleToGoal = Math.Atan2(nextGoal.Y - currPos.Y, nextGoal.X - currPos.X);
forceToApply.X = (float)Math.Cos(angleToGoal) * posUpdater.Speed;
forceToApply.Y = (float)Math.Sin(angleToGoal) * posUpdater.Speed;
float rotation = (float)(angleToGoal + Math.PI / 2);
posUpdater.Model.Body.Rotation = rotation;
if (!isAtGoal)
{
posUpdater.Model.Body.ApplyForce(forceToApply, posUpdater.Model.Body.Position);
posUpdater.forcedTowardsGoal = true;
}
if (isAtGoal)
{
// how can the body be stopped?
posUpdater.forcedTowardsGoal = false;
//posUpdater.Model.Body.SetLinearVelocity(new Vector2(0, 0));
//posUpdater.Model.Body.ApplyForce(-forceToApply, posUpdater.Model.Body.GetPosition());
posUpdater.Goals.Dequeue();
if (posUpdater.Goals.Count == 0)
{
return PathProgressionStatus.COMPLETE;
}
}
UPDATE
If I do keep track of how much force I've applied, it fails to account for other forces that may act on it.
I could use reflection and set _force to zero directly, but that feels dirty.
