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Selecting a polygon in the 3D view highlights the polygon/pile in the 3D view and allows you to see any base points that were used to analyze volumetrics on the pile.
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There are three methods for selecting a polygon a viewing it in the 3D view.
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You now can extrude piles from the base surface to get a better understanding of the material that is being included in your volumetrics calculations. To extrude a pile from the base simply Shift+Click the polygon and the pile will be extracted from the surface and displayed above the original pile. To remove the extruded pile, simply Shift+Click the same pile again.
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