physicsBody applyForce什么都不做

Question

我正在做这个视频教程： http://www.spritebuilder.com/getting-started/

一切正常，但是我射击的鸟没有速度。他们只是跌倒了。

希望你们有一个解决方案！提前谢谢！

这是我的lauchBird函数：

-(void)launchBird:(id)sender
{

//calc rotation
float rotationRadians = CC_DEGREES_TO_RADIANS(_launcher.rotation);


//vector for rotation
CGPoint directionVector = ccp(sinf(rotationRadians), cosf(rotationRadians));

CGPoint ballOffset = ccpMult(directionVector, 50);

//ball (bird)
CCNode* ball = [CCBReader load:@"Bird"];
ball.position = ccpAdd(_launcher.position, ballOffset);


//add ball to physicsNode
[_physicsNode addChild:ball];


//make impulse and apply force
CGPoint force = ccpMult(directionVector, 50000);
[ball.physicsBody applyForce:force];

}

Answer 1

正如Allen S所建议的那样，你需要在球上添加一个physicsBody。你可以通过

来做到这一点

int padding = 5;
CGFloat radius = 0.5*(ball.contentSize.width - padding);

//create a physics body

CCPhysicsBody* body = [CCPhysicsBody bodyWithCircleOfRadius:radius andCenter:ball.anchorPointInPoints];
body.density = 1.0;
body.friction = 0.5f;
ball.physicsBody = body; //assign the created body to the node's physicsBody property.

使用physicsBody的属性（密度，摩擦力，质量，弹性......）来获得理想的效果。