[osg-users] Why isn't OpenSceneGraph used in games?

[Robert Osfield]

Personally I don't feel it's games are critical to the success of scene
graph like the OpenSceneGraph.

Short lived game titles have very different focus that graphics application
that have a long shelf life.  A game will be developed then have year of
big sales, then perhaps might be followed up with iterations of the game,
but each iteration may well have completely different hardware/driver
target as a focus.

For long lived graphics applications you need to maintain your software for
a decade, perhaps even two.  Middleware and low level API's that such
applications depend upon have to live for similar periods of time if not
longer.  OpenGL has worked pretty well as a long lived low API, we've been
able to incrementally add and evolve features based upon new iterations of
OpenGL.  The OSG has evolved with OpenGL in this period.

Performance wise the OSG doesn't carry much overhead, if you are struggling
with performance it's almost always down to the scene graph that construct
not the library that is traversing that scene graph.  If performance sucks
in your application look to the optimizing the scene graph composition.

Being a general purpose scene graph does mean that the art part routes into
the OSG are also more general purpose than you'd get for a professional
game engine suite.  The later will be tailored for a particular art path
route, often with modelling tools specifically written for a particular
game engine.  It's this art path route that is what will affect the
massively affect the performance and productivity for game developers
working in the specific domain that game engine targets.  Out with that
sweet spot such game engine and modelling tool combo's will fail miserably.

There are parts of the OSG that don't perform well - the CPU path in
osgParticle for instance is well out of date.  For modern applications I
wouldn't use it save for the precipitation effects which are shader based
and perform really well.  For backwards compatibility sake it's still
useful to have the old osgParticle around.

Longer term Microsoft will loose even relevance, along with it Direct3D is
likely to wither away.  Vulkan looks well poised to work even better across
all platforms than OpenGL has, that will depend upon driver quality and
middle-ware just as OpenGL has.  Fingers crossed Intel etc. properly pull
their fingers out on this one.  As Vulkan is lower level that OpenGL there
is potential for middle-ware becoming more important for application
developers to help abstract away from the complex low level management or
memory, threading and state.

Right now OpenGL is still relevant to many application developers, and with
it the OSG is still relevant to many graphics developers, they might have
as much to splash around as AAA game developers but they span a huge market
range.  Had the OSG focused on games I suspect it would have just got
swamped by the rest of games market developers and lost relevance for the
rest of graphics developers around the world.  The world still needs scene
graphs, as a standalone scene graph is still one of the best.

Robert.
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