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我只是想不通这个大众的东西是如何运作的。我已经阅读了 box2d 文档（其中有许多命令目前不在 cocos2d 中）并且我试图理解大众的东西。

我知道，如果我改变身体密度，它不会改变任何事情：

    //add body
b2BodyDef spriteBodyDef;
spriteBodyDef.type =b2_dynamicBody; //b2_staticBody;
spriteBodyDef.position.Set(pilot1.position.x/PTM_RATIO,pilot1.position.y/PTM_RATIO);
spriteBodyDef.userData = pilot1;
pilot1Body = world->CreateBody(&spriteBodyDef);    
b2CircleShape spriteShape; //b2polygon-for box shape
spriteShape.m_radius = 15.0/PTM_RATIO;
b2FixtureDef spriteShapeDef;
spriteShapeDef.restitution = 0.4f;
spriteShapeDef.shape = &spriteShape;
//spriteShapeDef.density=10.0f;

b2Fixture *fix=pilot1Body->GetFixtureList();
fix->SetDensity(1.5f);
pilot1Body->ResetMassData();
NSLog(@"mass2: %f", pilot1Body->GetMass());  
spriteShapeDef.isSensor = false;
pilot1Body->CreateFixture(&spriteShapeDef);
    [self addChild:pilot1];

多谢。

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1 回答 1

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您需要为连接到身体的部分或全部灯具设置新的密度，b2Fixture::SetDensity然后调用b2Body::ResetMassData，例如：

    NSLog(@"mass1: %f", body->GetMass());
    b2Fixture *fix = body->GetFixtureList();
    while (fix) {
        fix->SetDensity(1.5f);
        fix = fix->GetNext();
    }
    body->ResetMassData();
    NSLog(@"mass2: %f", body->GetMass());
于 2012-01-27T22:51:55.927 回答