[osg-users] INVALID_OPERATION with compressed textures with mipmaps in OSG 3.4.0

[Robert Osfield]

Hi Scott,

The compression code has been in place quite some while so I'm surprised to
see a report of problem now.  Did this work with previous drivers/OSG
versions/different hardware?

Could you provide a small example and explanation of how to reproduce it so
others can see if they can reproduce the problem?

Thanks,
Robert.

On 22 September 2015 at 20:51, Davis, Timothy S CTR comnavairsyscom <
timothy.s.davis.ctr at navy.mil> wrote:

> I had an issue with OSG 3.4.0 when using a compressed 32x32 texture
> causing an INVALID_OPERATION in Texture::applyTexImage2D_load when calling
> glCompressTexSubImage2D.  This is called only when the texture storage
> object is used.  This resulted in the texture rendering as black.  Note
> that the texture was loaded from a IVE file created with an earlier version
> of OSG.
>
> After some investigation, I suspected that a possible cause was that the
> texture included mipmaps down to 2x2 and 1x1 in size.  The S3TC compression
> being used has a block size of 4 so cannot be used for these small mipmap
> levels.  Modifying numMipmapLevels by subtracting 2 if the image is
> compressed and using texture storage corrected the problem.  However this
> is likely not the best solution.
>
> My limited knowledge of OpenGL and this error suggests that this may be
> highly dependent on the OpenGL implementation.  I had several other
> compressed textures larger than 32x32 with mipmaps down to 2x2 and 1x1 that
> worked fine without this change.  The OpenGL documentation (see
> EXT_texture_compression_s3tc among others) however states that if the width
> or height are not multiples of 4 then the result is an INVALID_OPERATION.
> This can go unnoticed when not using a texture storage object.  But with
> the texture storage object, the error was generated when loading the full
> texture (i.e. level 0).
>
> If my understanding is correct, others may have had similar issues with
> compressed textures with mipmaps. They have worked around the issue by
> disabling mipmaps for compressed textures in ReaderWriterDDS for example.
> If the above holds true, then it may point to the underlying problem.
>
> Windows 7 64-bit, nVidia Driver 352.86, OSG 3.4.0
>
> Scott
>
>
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