[osg-users] osgdem --terrain vs polygon count?

Jean-Sébastien Guay jean-sebastien.guay at cm-labs.com
Mon Sep 29 08:20:53 PDT 2008

Hi Robert,

> The main speed up with using --terrain in the osgdem/vpbmaster build
> is that the tile geometry doesn't need to simplified - it can just be
> aquired from the source DEM's as grids and then output as grids.


> The key thing to remember with --terrain databases is that since the
> triangulation is done dynamically on load you do load balancing - you
> can set the Terrain::setSampleRatio() according to the hardware that
> you have

Ok, so in order to get --terrain databases to work optimally on all 
machines I would have to expose this setting in my software's config 
files (for example) so that it can be tweaked according to each 
machine's hardware, is that right?

I would suspect that on relatively flat terrain, the terrain database 
using simplified geometry might run fast enough on all machines (or all 
reasonably fast machines) without losing any relevant detail, whereas 
the --terrain database would be too slow on older machines, which would 
require that we lower the sampleRatio, and thus lose some detail? Is 
that possible?

In that case, if we need to support a large number of different hardware 
configurations, we might be willing to accept the longer build times of 
not using --terrain in exchange for not needing to tweak sampleRatio and 
not losing any detail.


Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com

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