Export Pix4d Volume - Import to autocad...How to create the solid

Does anyone export a volume from Pix4d, then import the volume mesh (3d polyline) Into Autocad?

I want a 3rd party who does not have Pix4d, to be able to verify  volumes. 

But converting an enormous amount of 3D Polylines into an actual 3d mesh seems to be very time consuming. Of course we can use the 3D textured mesh into a surface from tagging it. But really all i want to work with is the volume of a stockpile. 

How are others doing this?

I give my engineers contours and they are able to calculate volume in autocad with that information .

you can export the DSM and measure volumes in ArcGIS or QGIS 

 

Thanks guys. I use the contours as well. I have never worked with ArcGIS or QGIS. Is it fairly easy to pick up or is it going to be like learning autocad all over again?