[osg-submissions] Possible mipmap-bug for all kind of textures

[Robert Osfield]

HI Art,

This does sound like a bug, although not one that will be hit by most users..

W.r.t integer textures and mipmapping, one issue will be the
associated filtering, do you just assume the int is actually a float
do the filtering then cast back to int?

I would also wonder if glu's mipmap generation would support int textures.

I don't know what you are expecting in terms of functionality, with so
much on the OpenGL side not supported.

Robert.

On 9/7/07, Art Tevs <stud_info2 at yahoo.de> wrote:
> Hi Robert.
>
> I think I found  something wrong. Assume your hardware does not support
> glGenerateMipmapEXT. Now you create an empty texture (not from an image) and
> you want to be able to render to the mipmap levels of the texture through an
> fbo. So the mipmaps are never generated through the glTexImage* (level, ...)
> since there is no such call. For texture created from an image it works, but
> for empty texture it doesn't.
>
> If you also change your texture minification properties from non-mipmapped
> to mipmapped (e.g. NEAREST_MIPMAP_NEAREST) after the texture is already
> generated (i.e. in the next frame or after some time) then there is no code
> which checks for this changes to regenerate mipmap-levels.
>
> As I already said, this happens only if the hardware does not support
> glGenerateMipmapEXT, since otherwise it will be generated by the next call
> to the apply of the fbo.
>
> I am working on a workaround. I need this mipmap behaviour for the integer
> textures and it seems that the driver or hardware does not support automagic
> generation of mipmaps for integer textures. Even just a simple generation of
> mipmap levels with undefined data is not supported, if I am right.
>
> Art
>
>
>
>
>
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