[osg-users] NPOT Textures

Garrett Potts potts at cfl.rr.com
Wed Jul 9 04:56:56 PDT 2008

Hello All:

I use a custom visitor to enable a non power of 2 support.  This is  
very common from models I have seen from Google Sketchup.  I have ran  
across a number of non power of 2 textures and this seems to work  
nicely.  For some modes though, and I forget which,  it will still  
compute a power of 2 texture and I think this depends on the graphics  
card (Texture mirroring mode?).  I have an ATI card and it seems in  
OSG logic there are certain combinations of texture modes that still  
will cause a NPOT to be converted to a POT based on the testing of  
graphics card capabilities and assumptions.

Take care


> Hi Jim,
> It's the rendering thread that does the resize, and does so using glu,
> something that can only be called from a thread with a valid graphics
> context.
> To do rescale in a loader we'd need to implement scaling without the  
> use of glu.
> The other alternative is to just use the non power of two texture  
> extension.
> Robert.
> On Wed, Jul 9, 2008 at 1:47 AM, Jim Vaughan <jimv at fxpal.com> wrote:
>> Hi,
>> I have a related question; it seems that my textures are scaled as  
>> they
>> are loaded, for example if I move the camera, I get messages like:
>> 8)
>> Scaling image 'D:\DOTSModels\kmz\images\texture0.JPG' from  
>> (1600,1200) to (1024,
>> 1024)
>> Is there an easy way to cause all textures to be loaded and  
>> rescaled as the
>> model is loaded?
>> Thanks,
>> Jim
>>> -----Original Message-----
>>> From: osg-users-bounces at lists.openscenegraph.org
>>> [mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf
>>> Of Robert Osfield
>>> Sent: Monday, July 07, 2008 6:50 AM
>>> To: OpenSceneGraph Users
>>> Subject: Re: [osg-users] NPOT Textures
>>> Hi Paul,
>>> On Mon, Jul 7, 2008 at 1:15 PM,  <paul1492 at yahoo.com> wrote:
>>>> If my hardware supports NPOT textures, how do I turn off
>>> resizeNonPowerOfTwo when loading an OpenFlight file?
>>>> I don't see an easy way to do this..
>>> Using NPOT textures is only sensible to on hardware that genuinely
>>> supports it, otherwise it can force one down it software rendering.
>>> The Nvidia Gefore 6 series onwards all support proper NPOT.   I  
>>> don't
>>> know the status of ATI yet though.
>>> As for disable the automatic resize of non power of two textures,
>>> you'll need to write a NodeVisitor that goes through the scene graph
>>> and calls texture->setResizeNonPowerOfTwoHint(false);.  Perhaps the
>>> easiest step would be to be to extend the
>>> osgUtil::Optimizer::TextureVisitor so that it has an option for
>>> setting this value on/off, as this visitor already finds all the
>>> textures for you.
>>> Robert.
>>> _______________________________________________
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>>> negraph.org
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