Projectile movement using Box2d.

I need to know how to use box2d for projectile motion.

initially, projectileTime=0; then i call the following function for projectile motion. It works pretty good. 开发者_如何学CBut i want to achieve the same thing using box2d. As far as i know Box2d works only with force, it does not encourage placing object directly, So how to use Box2d for projectile movement??

-(void)projectilelaunched:(ccTime)dt 
{
    projectileTime+=(5*dt);

    double vh=v*cos(theta);

    x=vh*projectileTime;

    double y = x*tan(theta)- 10*((x/vh)*(x/vh))/2;

    projectile.position=ccp(projectilePositionBeforeLaunched.x + x,projectilePositionBeforeLaunched.y+y);

} 

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With box2D, you'd only need to set its initial position and initial velocity (via applyForce). Box2d will take care of the rest, applying gravity, stopping when hitting other objects etc.

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Actually, you can directly set up position of the body by calling:

body->SetTransform(vector,angle)

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b2Vec2 vector = self.speed * b2Vec2(cos(angle), sin(angle));

self.projectileBody->SetLinearVelocity(vector);