Flat vs. volumetric 3D symbol layers
This sample shows the visual difference between flat symbol layers and volumetric symbol layers when visualizing a 2D FeatureLayer in 3D, using IconSymbol3DLayer(flat) or ObjectSymbol3DLayer (volumetric). To visualize point symbols in 3D, you must use PointSymbol3D as the container of either an IconSymbol3DLayer or an ObjectSymbol3DLayer.
To learn more about symbol layers and the differences between flat and volumetric symbol layers, read the documentation on Symbol3DLayer. Also see the Labeling guide page for more information and known limitations.