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Jabberwocky wrote: Maybe we could leave the old _getDerivedPosition around for backwards compatibility.

jacmoe wrote:It's only common developer courtesy to not break a lot of peoples code and flag functions as deprecated for a while before removing them. Especially such a widely used function.

CABAListic wrote:You are right, though, getting the world position of a SceneNode is an important and imho necessary feature, and using the _getDerived methods may confuse people, particularly about the subtleties of the lazy update involved (although in most cases this will not be an actual issue).

I haven't looked at the SceneNode update code, so maybe this suggestion doesn't make sense. But I could imagine readding those getWorld... functions taken an optional parameter (bool forceUpdate = false) which, if enabled, will force the SceneNode hierarchy to update if necessary.

Jabberwocky wrote:Here's one possible solution:

Code: Select all

virtual const Vector3 & getWorldPosition( bool forceUpdate = false );

There should be some clear header comments as well, something like this:

Code: Select all

// Discuss how nodes in the hierarchy are lazily updated.
// Discuss the forceUpdate parameter, which can be set to true to force an update 
//      such that we consider any changes which have been made to our parent nodes.
// Discuss/warn about performance of using forceUpdate = true
virtual const Vector3 & getWorldPosition( bool forceUpdate = false );

Beauty wrote:Unfortunately this note isn't available in the class documentation.
So it would be good to add it to the description of SceneNode._getDerivedPosition(), _getDerivedOrientation() and _getDerivedScale().
Also for other classes which contains these functions (e.g. Bones).

Sinbad wrote:The issue here is that derived positions are lazy-updated for speed, not every time you make a change to nodes in the hierarchy. Thus the result may not be accurate unless SceneManager::updateSceneGraph has happened, or you force an update for a sub-branch of the tree. When you make a change to a parent node, the update flag is not propagated all the way down the tree (for the same efficiency reasons), it's just flagged as pending a cascade which is propagated later. Thus a node several children down may have no knowledge that it is currently out of date. Within 1 level of the tree it's ok, but beyond that it's not.

Without this lazy update approach, making lots of updates to scene objects in deep hierarchies becomes very slow. Thus we mark the _getDerived methods with an underscore because grabbing derived updates all the time can be both costly and /or inaccurate depending how you propagate changes. Scene managers can rely on them because updateSceneGraph has resolved all the changes.