[osg-users] Performance problems with a 'rear view mirror' view

[Murray Curtis]

I'm trying to include a rear view mirror view in my driving simulator 
scene but and having trouble getting reasonable performance.

I've recently converted from Producer to osgViewer and have set up two 
views on a common graphics context, one full screen, the other smaller, 
windowed over the other. Both share the same scene data but have 
different (opposite facing) view matrices.  It works just fine except 
the performance cost.

Its seems that CompositeViewer dosn't provide the useful statistic bar 
graphs that viewer has so I'm uncertain where the hit is but I'm 
guessing its the same cull/draw/gpu numbers again plus a little extra to 
manage the two overlapping viewports.

My first thought was I'd need to provide alternate scene data of a much 
lower resolution.  I made a utility based on osgSimplifier but even with 
textures at 10% the original and geometry reduced by > 50% (by file 
size) I get little if any improvement.  I'm now exploring going further 
back up the art path and producing lower res scene data there instead.

Typically the scenes I have take around the same time for draw and GPU 
and around 1/4 that for cull.

Am I going about this in the right way?  Any suggestions on a better 
approach? Could the viewports be the expense? Would a pre-render 
textured onto a quad be better?

Many thanks
Murray Curtis
Tag Systems
www.tagsystems.com.au