The InterpolationPoints have to be specified in ascending order of Data. They define a
graph of points. LookupValues less than the Data value of the first InterpolationPoint
are mapped to its corresponding Value. Accordingly, LookupValues greater than the
Data value of the last InterpolationPoint are mapped to the Value of this one.
LookupValues between two InterpolationPoints are interpolated between the
Only numeric quantities are allowed for LookupValue and Data. Values are usually
numeric as well. The interpolation of color-values requires the attribute mode="color" at
the Interpolate element.s