Translates to [code]smoothstep(edge0, edge1, x)[/code] in the shader language.
Returns [code]0.0[/code] if [code]x[/code] is smaller than [code]edge0[/code] and [code]1.0[/code] if [code]x[/code] is larger than [code]edge1[/code]. Otherwise the return value is interpolated between [code]0.0[/code] and [code]1.0[/code] using Hermite polynomials.