If creating a U3D PDF file from a dgn file containing shadows the shadows will preview but will not show in the U3D PDF file in Adobe Acrobat.
Adobe Acrobat does not support shadows in a U3D PDF. The preview is only somewhat accurate because it is a MicroStation rendering, not what Acrobat will truly display. The shadows do appear in Adobe Acrobat in a 2D PDF. Tested SELECTSeries 1 and using printer.pltcfg and hpglrtl.pltcfg and the shadows do plot to paper.