[osg-users] PagedLOD preprocessing

Paul Martz pmartz at skew-matrix.com
Mon Sep 10 11:15:21 PDT 2007

> > The problem is clear: OSG would probably freeze the computer during 
> > preprocessing when loading all the textures. In Inventor, it seemd
> > simple: just to override the texture type and make the 
> implementation 
> > not to load texture data. Any chance for solution in OSG?
> There every chance of a solution in the OSG, first up you 
> load the data, for instance do it incrementally, and then to 
> generate the LOD levels as required.  This is a tasks for you 
> to work out though - the OSG is a scene graph rather than a 
> modelling tool.

Hi Robert -- Assuming you've massaged your database so that the highest res
textures only get loaded/displayed at close ranges, how would you use OSG to
avoid the (seemingly inevitable) cost of loading the large texture from disk
and sending it over the bus to the graphics card when it is time to be
rendered? The naïve approach -- just let OSG load it -- appears to cause a
guaranteed frame rate hit.

I imagine you could break the texture up into smaller chunks and let OSG
page each in incrementally as it comes into range.

Or, you could preload all textures onto all displays at startup with the
GLObjectsVisitor, though this could tax system RAM for large datasets.

Could PROXY_TEXTURE help? At least it would tell OpenGL "hey, some big data
is coming, eventually" but there would still be the disk access and bus
transmission cost, so I imagine it's not a solution.

Robert, your thoughts please.

Paul Martz
Skew Matrix Software LLC
303 859 9466

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