The Distance Equation node adds to Equation 16-18, and the Distance Equation form contains the following sections for defining the length scale.

Select an option for the Reference length scale lref (SI unit: m): Automatic (the default) to use Equation 16-19 to compute lref, or Manual to enter a value in the field. The default value, when the scale is not computed automatically, is 1 m (when using SI units).