[osg-users] First steps to improve culling

[Alexandre Vaillancourt]

Hello forum/list!

We've been using openscenegraph for quite a while now, and now it's time to
start using it in a smarter way.

We've recently started to test displaying our app with 4 monitors: 3 in a
single Windows window (spanned over the 3 monitors of the same graphics
card with NVidia surround), and a 4 monitor with another Windows window on
a second graphics card.

Our test app can now run with 1, 2, 3 and 4 monitors, and thus the same
amount of camera displaying the scene.

Now as it's expected, as more cameras are added, the framerate starts to go
down.

With the Visual Studio (2013) profiler, I've narrowed down the core of the
time spent in OSG's 'frame' call is during the cull stage.

A couple of fact:
- The app is a Forklift Simulator
- The essential of the time is spent in the virtual warehouse
- The warehouse is full of loads
- Racks and Loads have no LODs (this could be improved)
- Racks and Loads (specifically) are not optimized geometry-wise, their
poly count could be reduced (this could be improved)
- In the scene graph, all the loads are siblings under a parent
'LoadsShadowedNode' group node

The big question is:
How can I reduce the time spent culling? Are the obvious "create LODs" and
"optimize your loads graphics" that effective? Could I rethink how the
loads are organized in the scene graph? If so, in what way? Any clue as
what would bring the most bang for my buck?

Any clue will be welcome :)

I'm not that familiar with the inner workings of OpenGL and I realize I
should push my knowledge a bit more.

I have attached a couple of screenshot to give an idea of what the software
looks like.

Thanks for any help!

--
Alexandre Vaillancourt
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