Now you see it now you don't

I was importing an AutoCAD dwg file into Revit 2009 for some project for my client. It looks OK on floor plan.


However, in 3D view, the screen just go blank with no Revit entities nor AutoCAD entities on sight. No amount of setting changes will make the drawing appear.

The mystery was finally revealed when I open up the AutoCAD file in AutoCAD. It appears that some part of the CAD drawing are having unusually high and low points. Even in AutoCAD the iso view does not display the drawing entities as well. After I edit the elevation of all the lines and blocks, then the drawing appear as per normal.

This apparently is only a problem in AutoCAD and Revit 2009. Seems that the display would not work properly when there are irregular Z points in version 2009 but other version will display the drawing with the irregular points. So, if your 3D view in Revit suddenly goes blank, please check your imported CAD drawing for a ny irregular points.