[osg-users] [osgPlugins] DDS textures not loading on Mac OSX and the latest trunk(3.5.0)

[Robert Osfield]

Hi Curtis,

On 18 August 2015 at 14:58, Curtis Rubel <crubel at compro.net> wrote:

>    With things the way they are now, its very strange.  I have a few sets
> of flight files that work and also a set that does not.  The dropbox
> link I put in my last post for the small flight test case, the dds textures
> do not load on the mac.   So it seems that this is not failing with
> all cases of pre-generated mipmaps.  Maybe there is something
> in how this was done in older versus newer versions of openflight
> or something.
>

The way to look into this would be to take the same source model and
convert it to .osgt with the older version and the new version and then
compare.



>
> What is the difference between using the pre-gen'd mipmaps and not
> using them?  Is there some sort of performance boost if the
> pre-gen'd ones are working properly, something has to be
> calculated on the fly as they are loading or something?
>

Pre-generated mipmaps are more efficient for downloading to the GPU.

The alternative is to use glu to generate the mipmaps or get the driver/GPU
to compute them.  All these opertions will end up with the same
representation on the GPU as pre-generated mipmaps so the final memory
footprint, visual quality and performance will be the same, the only
difference will the CPU or GPU overhead associated with generating the
mipmaps on the fly.

For a real-time graphics application the difference you'd see if that
pre-generated mipmaps are less likely to cause a frame break when the
texture is download for the first time.

Robert.
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