The minimum scale at which labels will be visible. In 3D scenes, the scale range is between individual label and view plane instead of map and view plane. Labels will only be visible when the viewing scale is larger than (or equal to) the minScale.
For example, if the viewing scale is 1:12000 and the LabelDefinition.minScale is 1:20000, then the labels will be visible (because 1/12000 >= 1/20000). A LabelDefinition.minScale of 0, which is the default, indicates no lower limit on the viewing scale.