[osg-users] When optimizing with LOD changes, should I change UV map resolutions?

Paul Martz pmartz at skew-matrix.com
Thu Jul 10 08:26:01 PDT 2008


Robert's comment regarding texture atlas usage in low-res LOD children is an
excellent suggestion.
 
Going further, your post begs the question: Do you suspect that texture
memory usage is the bottleneck to your performance? One way to test this (if
you haven't already done so) is to set the OSG environment variable to limit
the maximum texture dimension to something ridiculously small. If your app
runs faster with this setting, then texture memory usage might be causing
performance problems, and you might need to address that in some way.
 
You should keep in mind that most OpenGL device drivers are smart enough to
page out large mipmap levels when they are not in use.
 
Another thing to keep in mind is that a texture never needs to be larger
than its max representation on-screen. For example, it's pointless to have a
2kx2k texture applied to an object that will never subtend more than 500x500
pixels.
 
Hope that helps.
   -Paul
 


  _____  

From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of
rpingry at gmail.com
Sent: Thursday, July 10, 2008 7:09 AM
To: OpenSceneGraph Users
Subject: [osg-users] When optimizing with LOD changes,should I change UV map
resolutions?


Hello All,
 
I have been trying to get my scenes to run faster, balancing my scene graphs
using LOD.  I use quite a bit of UV mapping in my models, and they can be
fairly high res because I want them to look good up close.  There are
usually several instances of the same model in the scene, all pointing to
the same scene graph.  I was wondering about the best way to create LOD
changes for them.  I was going to cut out some polygons, but I was also
thinking of cutting the resolution back on the UV maps.  Is this valuable?
On first assessment, it seems it would be, but then I realize that it might
cause MORE of a memory usage, and the graphics card (or OSG) might be doing
this kind of optimization anyway (dropping image map resolutions based on
pixel size or whatever).  What are your recommendations?

-- Thanks for everything
>> Rick
Check us out at http://fringe-online.com/ 

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