Getting normal when using spherical coordinates

[oveddan]

Lets say you have a function that evaluates a location in spherical coordinates, and gives you the offset from a sphere surface that the point exists on.

In my case it's a noise function that takes three angles and returns the "height" - essentially the offset from the standard position that the point would exist on in the sphere.

How would you compute normal of that point using this noise function?

[oveddan]

Figured it out - just sample the changed point at that offset from the sphere, and use those as the dx/dy