'Nabla' setting for cloud texture What does the 'Nabla' setting for a cloud texture do? 

Nothing seems to be changing when i change the value. I'm tweaking a texture and i'm just curious how i can tweak it even better. 

The tooltip says: Size of derivative offset used for calculating normal.
In order to calculate a normal, you can decide to take three samples in texture space. Typically that's the current sample location, and two other positions in texture U and V directions. This "nabla" value defines how far away these positions are. You will see how it works best on a high frequency procedural texture.

Typically tiny nabla values give minimal normal changes. Optimal is half the texture frequency (which you have to figure out by guessing unfortunately :).