Gradient Noise

Ported from: https://www.iquilezles.org/www/articles/gradientnoise/gradientnoise.htm

The noise function is imported, but we then need to set up a proxy function. This is because the macro system relies on inlining, and we want to create a function definition, not just inline the noise code at the point of use.

  inline def fragment =
    Shader[FragmentEnv] { env =>
      import ultraviolet.noise.*

      def proxy: vec2 => vec3 =
        p => gradient(p)

      def fragment(color: vec4): vec4 =
        vec4(proxy(env.UV * 8.0f), 1.0f)
    }