SimpleMotionPath  - AS3 Flex

Optional property which specifies the delta used to calculate either the valueFrom or valueTo value. Providing this optional property lets the effect calculate the necessary from/to values if either are not provided or are to be determined dynamically when the animation begins.

The way that the valueBy value is used depends on which of the other values are set. If neither are set, then the valueFrom value is determined from the current property value in the target, and the valueTo value is valueFrom + valueBy. If one or the other is set, but not both, then the unset value is calculated by the other value: valueTo = valueFrom + valueBy or valueFrom = valueTo - valueBy). If both are set, then the valueBy property is ignored.

Note that since valueBy is of type Object, the effect cannot directly calculate the other values from it. It uses the effect's interpolator to calculate the values by calling the interpolator's increment() and decrement() methods. If no interpolator is set, then it will use NumberInterpolator by default.

The starting value for the property during the animation.

A value of Null or NaN (in the case of Numbers) specifies that a value must be determined dynamically at runtime, either by getting the value from the target property directly or calculating it if the other value is valid and there is also a valid valueBy value supplied.

The value that the named property will animate to.

A value of Null or NaN (in the case of Numbers) element specifies that a value must be determined dynamically at runtime, either by getting the value from the target property directly or calculating it if the other value is valid and there is also a valid valueBy value supplied.

Constructor. You can specify both the valueFrom and valueTo parameters, or specify the valueBy parameter and either the valueFrom or valueTo parameter. If you omit these parameters, Flex calculates them from the effect target.