Strange issue with PhysicsBody and Animation

cocos2d-x C++
#1

Hi guys,
In cocos2d-x 3.0RC i’ve found a strange behaviour with PhysicsBody.

If i create my Sprite:

Sprite *par = Sprite::create();
par->setColor(Color3B(0.0f, 255.0f, 0.0f));
par->setPosition(Point(visibleSize.width * 0.5f,visibleSize.height * 0.5f));
par->setAnchorPoint(Point(0.5f, 0.5f));
par->setTextureRect(cocos2d::Rect(0, 0, 600, 80));

//add child here

MoveBy *animation = MoveBy::create(4.0f, Point(0, -300));
par->runAction(animation);
this->addChild(par);

It works like a charm.

But if i add a child with a PhysicsBody attached, this child simply doesn’t move (but the parent yes).

//A method that return a sprite
Sprite *obstacle = ObstaclesMaker::obstacle(Point(300, 0), Size(300,50));

Size size = obstacle->getBoundingBox().size;

PhysicsBody *obstacleBody = PhysicsBody::createBox(size);
obstacleBody->setDynamic(false);
obstacleBody->setRotationEnable(false);
obstacleBody->setGravityEnable(false);
obstacleBody->setPositionOffset(Vect::ANCHOR_MIDDLE);
obstacleBody->setCategoryBitmask(MainGameColliderTypeWay);
//obstacleBody->setContactTestBitmask(MainGameColliderTypePlayer);
obstacle->setPhysicsBody(obstacleBody);

par->addChild(obstacle);

How to add a child with PhysicsBody and move only the parent?
Gravity and dynamics are disabled, it would work like a trigger.

Thanks

#2

I’ve found PhysicsSprite but it doesn’t works and my app crash!

cocos2d::extension::PhysicsSprite *obstacle = cocos2d::extension::PhysicsSprite::create();
obstacle->setColor(Color3B(255.0f, 255.0f, 0.0f));
//obstacle->setPosition(Point(0, 0));
obstacle->setAnchorPoint(Point(0.5f, 0.5f));
obstacle->setTextureRect(cocos2d::Rect(0, 0, 300, 40));

Please, help me!

#3

I’ve found a solution!

In PhysicsBody class i’ve edited the “update” function:

void PhysicsBody::update(float delta)
{
    if (_node != nullptr)
    {
#warning edited according to https://github.com/cocos2d/cocos2d-x/pull/5593/files
        Node* parent = _node->getParent();
    
        Point position = parent != nullptr ? parent->convertToNodeSpace(_node->getPosition()) : _node->getPosition();
    
    
        _positionResetTag = false;
        _rotationResetTag = true;
    
        if (parent != nullptr && !isDynamic()) {
        
            Point bodyPos = parent->convertToWorldSpace(_node->getPosition());
        
            setPosition(bodyPos + _positionOffset);

        }else{
            _node->setPosition(position);
        }
        _node->setRotation(getRotation());
        _positionResetTag = false;
        _rotationResetTag = false;
    
    
        // damping compute
        if (_isDamping && _dynamic && !isResting())
        {
            _info->getBody()->v.x *= cpfclamp(1.0f - delta * _linearDamping, 0.0f, 1.0f);
            _info->getBody()->v.y *= cpfclamp(1.0f - delta * _linearDamping, 0.0f, 1.0f);
            _info->getBody()->w *= cpfclamp(1.0f - delta * _angularDamping, 0.0f, 1.0f);
        }
    }
}

Now if you add a Sprite with a PhysicsBody as a child of a Sprite with a PhysicsBody, the child follow the parent as expected during animation.