[osg-users] viewport is changing after huge sized object ; updating only visible nodes

Sebastian Messerschmidt sebastian.messerschmidt at gmx.de
Mon Mar 28 05:05:58 PDT 2016

> Hi Andrey,
> On 22 March 2016 at 09:30, Andrey Perper <TheAndreyp at gmail.com 
> <mailto:TheAndreyp at gmail.com>> wrote:
>     Hey guys!!!!!!!
>     1) My scene is set like it is always fits in camera (i guess it is
>     osg-default). If i add huge sized object - i see all scene (camera
>     flies away), but my viewpoint must stay old.
>     How to fix that ?
> First thing is to clarify the language.  In OpenGL and therefore the 
> OSG the viewport (glViewport / osg::Viewport) is the rectangular 
> region of the window that the rendering fills in.
> What you are describing is the Viewer's CameraManipulator changing 
> it's view matrix, which wrap up the eye, center and up direction) so 
> the whole scene is encompassed.  This reset of the CameraManipulator 
> happens in the home() method.  For most applications that just won't 
> to use one of the standard CamaeraManipualators (found in the osgGA 
> library) re-positing the view is appropriate.
> For your specific usage case it sounds like this is not desired.  
> CameraManipulators in the OSG are just optional so you can set the 
> View's master Camera view matrix directly, or for you to create your 
> own custom CameraManipulator, or to subclass from one of the osgGA 
> CameraManipulator's and override the methods that you want to modify 
> the behaviour of.
> I can't say what approach is most appropriate as I know too little 
> about the specifics of your application.
>     2) I have dozen of nodes that are updating in my addUpdateCallback
>     functor anyway (whether node is visible or not), but i would want
>     to do that only if node is visible. Node has osg::Geode drawables.
>     How to fix that ?
> I'm not clear on what you mean here.
I guess he wants to have the updateCallback called for "culled" geodes, 
or some way to check if the node was culled.
> Robert.
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