Previously, only Paints of type Color gave a 3D-effect
in BarRenderer3D, StackedBarRenderer3D & PiePlot3D.
The Color.darker() method-call has been replaced with a new class,
PaintAlpha which extends the \\\"darker\\\" functionality to ALL known Paints.
Also, transparency (even in Color types) resulted in \\\"flat\\\" 3D effects.
PaintAlpha respects the alpha-channel, while darkening the colour-channels.
The end-result is a much improved 3D experience.
(take a look at the screenshots to see the difference)