noised

void  noised(float x, float &v, float &dvdx)

void  noised(float x, vector &v, vector &dvdx)

void  noised(float x, float y, float &v, float &dvdx, float &dvdy)

void  noised(float x, float y, vector &v, vector &dvdx, vector &dvdy)

void  noised(vector xyz, float &v, float &dvdx, float &dvdy, float &dvdz)

void  noised(vector xyz, vector &v, vector &dvdx, vector &dvdy, vector &dvdz)

void  noised(vector4 xyzw, float &v, float &dvdx, float &dvdy, float &dvdz, float &dvdw)

void  noised(vector4 xyzw, vector &v, vector &dvdx, vector &dvdy, vector &dvdz, vector &dvdw)

This computes both the perlin noise value, and the derivatives of the noise along each axis. This can be performed quite efficiently as there are analytic derivatives available.

See noise and randomness in the VEX language guide for more information.