[osg-users] Adding a child to a node at runtime.

[Thrall, Bryan]

James Reid wrote on Thursday, June 19, 2008 12:13 PM:

> Howdy!
> 
>     When I try to add a child to a node at runtime I get an exception.

> Unfortunately, the exception dies quietly so I'm not sure what the
actual
> exception is.  I know I've done this before (a long time ago) and
things have
> changed since then, so I'm not sure what I'm doing wrong.  Here's the
setup
> of our app.    
> 
> We're rendering on a managed window using managed c++
> We have a button that enables/disable certain graphics to be drawn.
> To do the hiding of a graphic, I remove the geode from it's parent
node.
> To do the showing of a graphic, I add the geode to the parent. <- this
causes
> the exception 
> 
> We're building a simulation and our users can toggle certain graphics
on/off.
> For example, they can view graphic, physics, center of mass,
constraints,
> etc...  They can view any number of these at any time.  
> 
> My current set up is I have a Geode for each representation.  I then
> add/remove that geode depending on the display settings. 
> 
> Is this the wrong setup?  I've searched for similar solutions and
haven't
> really found anything.  Maybe I'm looking in the wrong places? 

It isn't safe to modify the scenegraph during the cull and draw passes;
it's best to use a UpdateCallback, or to replace your call to frame()
with your own that modifies the scenegraph before doing the cull and
draw.

There are other ways to show/hide geometry, such as the node mask or a
CullCallback; not that what you're doing is wrong, but perhaps they
might do what you want better.

-- 
Bryan Thrall
FlightSafety International
bryan.thrall at flightsafety.com