Hello,
I have been working on switching over to ON_DEMAND frame updates while
using osgViewer::Viewer and I encountered the following problems (all of
these issues are specific to ON_DEMAND frame updates):
1. Some of the event handlers such as osgViewer::HelpHandler, and
osgViewer::ScreenCaptureHandler (maybe others) do not request a new
frame explicitly after their keyboard events are triggered. However, a
number of the event handlers in the same folder do (such as the
StatsHandler). Thus, the HelpHandler does nothing until something else
triggers a frame update. If I add another event handler before the
HelpHandler and call osgGA::GUIActionAdapter::requestRedraw() when "h"
is pressed, then the behavior is similar to that of the StatsHandler,
and the first key press does not seem to have any effect (see
StatsHandler behavior below), but all subsequent key presses work as
expected.
2. The StatsHandler does not show up after pressing "s" the first time.
Every subsequent time "s" is pressed, the StatsHandler behaves as expected.
3. The default behavior of Viewer::checkNeedToDoFrame() makes it
difficult to use with scene graphs that contain UpdateCallbacks because
there is no easy way that I have found to disable or modify the
getNumChildrenRequiringUpdateTraversal() check (without deriving).
Some example code:
osg::ref_ptr <osgViewer::Viewer> viewer (new osgViewer::Viewer ());
// Setup viewer camera and context here...
// ...
viewer->addEventHandler (new osgViewer::StatsHandler ());
viewer->setRunFrameScheme (osgViewer::ViewerBase::ON_DEMAND);
viewer->run ();
I did override the osgViewer::Viewer::checkNeedToDoFrame() behavior to
skip the UpdateCallback check (so frames were not continuously rendered
as a result) in order to address issue #3 above.
Thank you,
Judson
_______________________________________________
osg-users mailing list
osg-users@lists.openscenegraph.org
http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
