Adding custom parent/child relation in a new ISceneNode

[jockey]

hi,

Am creating my own scenenode (CMyNode) and have a question about the children and rendering a node without any parent. Since I am learning the engine, I need some preventive advice.

The scenenode contains his own custom scenenodes (CMyOtherNode). These 'children' scenenodes shouldn't be accesible outside of this cMyNode class. Therfor the parent of the CMyOtherNode isn't set to the instance of CMyNode nor it it set to sceneManager->getRootSceneNode(). They are not added to ISceneNode::Children but to an array member.

Since both classes decent from ISceneNode I have overridden the OnRegisterSceneNode, as below, for both. Now all m_myOthers are rendered too, yeah.

My question: Is this correct or am I heading towards a nasty bug in my application?

Code: Select all

 
class CMyOtherNode;
class CMyNode : public scene::ISceneNode
{
    core::array<CMyOtherNode*> m_myOthers; // can have nulled entries
    
    public:
    CMyNode ::CMyNode(...) : ISceneNode( parent, sceneManager, id, position, rotation, scale )
    {
 
        for( u32 i = 0; i < 4; --i )
        {
 
            // Add other
            CMyOtherNode* other = new CMyOtherNode( 0, SceneManager ); // No parent!
            m_myOthers.push_back( other );
 
        }
 
    }
    void OnRegisterSceneNode()
    {
         // Same for CMyOtherNode
 
            if( IsVisible )
            {
 
                SceneManager->registerNodeForRendering( this );
 
                u32 size = m_myOthers.size();
                for( u32 i = 0; i < size; ++i )
                    m_myOthers[ i ]->OnRegisterSceneNode();
 
            }
 
        ISceneNode::OnRegisterSceneNode();
 
    }
}
 

[CuteAlien]

Absolute position functions will likely not regard the parent if it's not a real parent. Not sure if you need that.

[jockey]

After a quick glance I have rewritten the OnRegisterSceneNode of CMyOtherSceneNode. It does work although it seems a bit lame. There must be a better solution to this.

Code: Select all

 
    CMyNode* CMyOtherNode::m_myNodeParent = instance CMyNode; // ISceneNode::Parent is still 0
    void CMyOtherNode::OnRegisterSceneNode()
    {
 
        if( IsVisible )
        {
 
            setPosition( m_myNodeParent->getAbsolutePosition() );
            setRotation( m_myNodeParent->getAbsoluteTransformation().getRotationDegrees() );
            setScale( m_myNodeParent->getAbsoluteTransformation().getScale() );
            updateAbsolutePosition();
 
            SceneManager->registerNodeForRendering( this );
 
        }
 
        ISceneNode::OnRegisterSceneNode();
 
    }
 

[Mel]

When Irrlicht processes the node hierarchies, the nodes create their local transformation matrix out of the rotation, position and scale vectors, which then multiply by its parent's local transformation matrix to get their own correct transformation, in a nutshell. This goes down to the child list and so on and that's how things go. This is done in the "OnAnimate" method.

What i wonder is what kind of hierarchy do you need that you have to create your own list of nodes to store another nodes? Irrlicht scene nodes handle this on their own very well. It is simpler to just link the nodes as child nodes and process them elsewhere keeping a track of their pointers, but that is what i would do anyway