In this article Nokola demonstrates the usage of Simplex noise and provides source code which contains both 2D and 3D Pixel shader Simplex noise implementation.
The "Noise" can be used to make effects such as fire, water,
marbles, smooth motion, hand-drawn UI, space travel effects, nebulas
and a lot more!
Simplex noise has similar characteristics to Perlin noise - it's
continuous, smooth and its first derivative is smooth too. The nice
thing about the Simplex, is that its much easier to compute and thus
can be implemented in Pixel shaders.