Hi all,
have I overlooked something or doesn't OSG have methods to control sync-to-vblank at
runtime? GraphicsContext has a 'vsync' member but the only location where that is used is
in GraphicsWindowCarbon and is only checked once during context setup (realizeImplementation).
Effectively there is no way that I know of to turn vsync off on OS X short of modifying
the code. Windows and Linux can at least control it using driver settings or environment
variables.
My first idea was to add a 'set/getSyncToVBlank' method to GraphicsWindow that would
record the new setting in the traits (if valid) and enable/disable vsync as necessary (I
have it working for OS X using aglSwapInterval; Win32 could use wglSwapIntervalEXT and
Linux glXSwapInterval/glXGetVideoSyncSGI/glXWaitVideoSyncSGI).
But traits can be shared among different contexts and this implementation would do the
wrong thing: it would turn vsync on for the one GraphicsWindow called but not any others
sharing the same traits. It would however report the new vsync setting for all of them;
certainly not desirable.
So my questions are:
- did I miss existing support for vsync?
- does it make sense for different contexts to have different vsync setting?
- what about off-screen/RTT contexts? Surely they don't need that, but they don't call
SwapBuffers anyway.
- what about multiple on-screen contexts like multi-screen setups? Does that need extra
synchronization?
Thoughts?
Cheers,
/ulrich
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