Simplex Noise Shader not working in SFML

[Nutomic]

I am trying to create a shader using simplex noise, based on webgl-noise.

However, the effect doesn't shows some clear patterns in SFML.

Here is how it looks in the project's example:


Here's what it looks like in my SFML project (using the exact same shader):


Here's my SFML code link

And here are the shaders: noisedemo.vert noisedemo.frag

The shaders are exactly the same as in the webgl-noise example.