The z-coordinate at which to place this material relative to its parent.
This controls the size of the shadow below the material and the opacity of the elevation overlay color if it is applied.
If this is non-zero, the contents of the material are clipped, because the widget conceptually defines an independent printed piece of material.
Defaults to 0. Changing this value will cause the shadow and the elevation overlay to animate over animationDuration.
The value is non-negative.
final double elevation