I've been googling for two days looking for info on using texture2DGrad() in glsl, and all I've found so far is mentions in forums that it is not yet supported; but the posts are a year old or more. Has this changed by now, I hope?
I'd also appreciate if someone could pass me links to code examples using anisotropy. I'm thinking of using anisotropy in 4 ways (not sure if all are possible):
1) Standard way, for anisotropic texture blurring to avoid view angle artifacts
And anisotropic blurring of the environment cube-map for...
2) Material anisotropy, such as standard brush metal finish on stainless sheets.
3) Environment reflections on anisotropically curved surfaces, based on reflective surface curvature (change of normal in screen-space).
4) For ambient light extraction from the environment in the cases of stretched/flattened openings in the ambient occlusion space, which are quite common.
But I've never used anisotropy before, in glsl; I'm not even sure if texture2DGrad() is the way to do it. And would there be such thing as a textureCubeGrad()? And what about LOD? Would Grad variants imply LOD control (like for shininess modulation)?