Unfortunately the current version of the Silverlight 3D Pie chart does not support interactive features like animations and tooltips and it cannot be customized to achieve the desired effect. We will research our options how to implement such features for our 3D series once Silverlight implements native hardware-accelerated 3D support in one of the future versions of the framework (as you are probably aware Silverlight does not provide support for real 3D graphics out-of-the-box at the moment and RadChart relies on our own proprietary 3D engine that has certain limitations).
For 2D Pie series you can achieve the desired effect by setting the PieSeriesDefinition.ShowItemToolTips property to true.
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