Hi Tugkan, On Wed, Sep 3, 2008 at 9:56 AM, Tugkan Calapoglu <[EMAIL PROTECTED]> wrote: > I am porting an application from OSG0.99 to latest SVN version.
Wow, climb aboard the time machine :-) > I have two > questions (both for CullThreadPerCameraDrawThreadPerContext mode): > > 1- Is it safe to make changes in the scene graph outside the frame call > (without using update etc. callbacks )? Or is the only place where we have > safe scene graph acess is inside a callback? Mailing list and source code > reading made me think that outside the frame() should be safe but I am > getting some crashes. Before delving into my own code I'd like that someone > confirms this. Modifying the scene graph outside of the frame call is safe in SingleThreader, and CullDrawThreadPerCamera threading models as they don't leave any threads active after the end of the renderingTraversals() method (called from frame()). With DrawThreadPerContext and CullThreadPerCamewraDrawThreadPerContext the draw threads will still be active on completion of the renderingTraversals(), so if you modifying drawables and state that the thread is still reading from in the draw traversal you will end up with problems - and potential crashes. There is a standard mechanism to deal with this issue - and that is the renderingTraversals() method to block till all dynamic objects in the draw traversals have been dispatched. The way you tell the draw traversal that an drawable or stateset will be modified dynamically is to set its data variance to DYNAMIC. drawable->setDataVariance(osg::Object::DYNAMIC); stateset->setDataVariance(osg::Object::DYNAMIC); This is mentioned in the "Quick Start Guide" book, as well as many times on the osg-users mailing list so have a look through the archives if you want more background reading. > 2- Is it ok to change the global state set during rendering outside frame > call? I have following code runing before frame() is called : > > osg::Camera* cam = getViewer()->getView(i)->getCamera(); > cam->getOrCreateStateSet()->clear(); > cam->getOrCreateStateSet()->setGlobalDefaults(); > ... And some other changes ... Same requirement - if you are modifying the stateset then you'll need to set its data variance to DYNAMIC. For a StateSet that decorates the whole scene graph you'll end you holding back the frame till the whole scene graph is completed, so it won't have any performance advantage over CullDrawThreadPerContext. You can double buffer objects to allow you to retain the STATIC data variance and keep the threads overlapping, to do this you do: osg::Camera* cam = getViewer()->getView(i)->getCamera(); cam->setStateSet() = new StateSet; // this is where we just use a new StateSet rather than modify the previous one cam->getOrCreateStateSet()->setGlobalDefaults(); ... And some other changes ... The draw traversal takes a reference to the StateSet and Drawables so it's safe to go an remove them from the scene graph outside the frame() call, this isn't something makes then dynamic so you won't need to set their data variance to DYNAMIC. Robert. Robert. _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
