Drawing 3d polygon element on Arcobject axSceneControl?

Question

I have standalone application (ArcObjects C# 10.1) uses axSceneControl. How to display on the scene 3d polygon elements? I have implemented drawing 3D line elements using ISimpleLIne3DSymbol. I tried to use PolygonElement to add to AxSceneControl, but the element has no elevation.

long pColor = Vsur.GIS.Element.ColorConvert.ConvertColor(System.Drawing.Color.Blue);
IElement pElement = ElementOperate.CreatePolygonElement(geo, pColor, esriSimpleFillStyle.esriSFSDiagonalCross, pColor, esriSimpleLineStyle.esriSLSNull, 0.5, false, "OPERA");
IGraphicsContainer3D pGCon3D = pSceneControl.Scene.BasicGraphicsLayer as IGraphicsContainer3D;
pGCon3D.AddElement(pElement);