Calculates a scalar derivative within the visual shader graph. This node is only available in [code]Fragment[/code] and [code]Light[/code] visual shaders. The derivative type. See [enum Function] for options. Sum of absolute derivative in [code]x[/code] and [code]y[/code]. Derivative in [code]x[/code] using local differencing. Derivative in [code]y[/code] using local differencing.