factor
The factor grows from -1 to 0 to 1. The slope depend on the start and end parameters of the class.
relativeDistance < -end -> -1frelativeDistance in -end..-start -> -1f..0frelativeDistance in -start..start -> 0frelativeDistance in start..end -> 0f..1frelativeDistance > end -> 1fif abs(relativeDistance) in start..endthe factor changes linear.