Box2d Apply force in a certain direction

Question

I want to apply force to my object in the direction that it is now, here is my code so far, but it throws errors when I try to do force * t , what am I doing wrong?

  b2Transform t; t.Set(b2Vec2(0, 0), spaceCraft->GetAngle()); b2Vec2 force = b2Vec2(0, 2.5f); spaceCraft->ApplyForce(force * t, spaceCraft->GetPosition()); 

Answer 1

The easiest way is to look at the direction the object “collides” when you define the body, and use GetWorldVector to see how it changes. For example, if it is facing straight up, when you create a body, this will be the direction (0,1). Then you can use GetWorldVector at any time to get the current direction of this vector in world coordinates to apply force:

 b2Vec2 forceDirection = body->GetWorldVector( b2Vec2(0,1) ); 

Answer 2

I can't try it right now, but something like that:

 float magnitude=2.5f; b2Vec2 force = b2Vec2(cos(spaceCraft->GetAngle()) * magnitude , sin(spaceCraft->GetAngle()) * magnitude); spaceCraft->ApplyForce(force, spaceCraft->GetPosition()); 

Answer 3

You can try as suggested by IFORCE2D

 float mangnitude = anything; b2Vec2 forceDirection = body->GetWorldVector( b2Vec2(0,1) ); forceDirection = magnitude * forceDirection; body->ApplyLinearImpulse(forceDirection, body->GetPosition(), true);