Question

我只是无法弄清楚这种大众的运作方式。我已经阅读了box2d文档，（其中有许多命令目前不在cocos2d中），我试图理解质量的东西。

我知道，如果我改变身体密度，它就不会改变一件事：

    //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];

非常感谢。

Answer 1

您需要使用b2Fixture::SetDensity为贴在身体上的部分或全部灯具设置新的密度，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());

使用box2d cocos2d不改变体重

1 个答案: