how can I show big texture, say, 4096x2048 ?
By splitting it into several smaller textures.
Using a graphiccard that supports this resolution 
nvidia 5 series and higher should support it.
Matthias
Maybe i’m out but my NV25 (yes, geforce3 family) supports 4Kx4K. I tried it loading 8Kx8K and it only got resized to half dimension by the texture management.
I raccomand to resize the texture if still too big. While this loses some detail, it’s often much easier to manage, especially when the whole thing becomes much more complicated (shaders and stuff, you know).
Splitting it requires to re-parse the geometry at runtime, which is not necessarly bad but could have some problems.
Another method I’ve used is to load the separate components as individual single component textures. Often hardware will support larger single component textures than they will 3 component textures. You can then render the individual channels using multiple passes and color buffer writemasks.
dorbie: how can I do it ? Say, I split RGBA array into R[], G[], B[], and alpha[]. And then … ?
(I am a newbie in OpenGL).
Thanks.