Trim 3D polyline on a surface

[berny1504]

Hi,

I need help with this problem:

I have a big XYZ file (3D points) imported in autocad. I have to draw some simple 3D object on the surface generated by these points. The points descrive a regular non planar surface. 

I have to cut the 3D object in such a way that it stops in correspondance of the surface and then export the modified surface again in points like file (the XYZ is the imput file of another program). 

I have tried to draw the 3D object with 3Dpoly and to build the surface under it with loft function, but i don't know how to trim it. 

I'm not confident with Autocad3D, can you please give me some suggestion?

Thank you

[TomBeauford]

Calculating volumes from surfaces like that is fairly simple with Civil 3D. I'd question the accuracy doing it any other way.

[berny1504]

Con you please give me an idea of the command I should use to interpolate the surface in civil 3D, trim them and extract XYZ points so I can study and try them. Maybe I can download civil 3d with the

university license, but I have never used it and have no idea on how to work with it.

Thank you

[TomBeauford]

Online search for civil 3d volume calculation returns many options but Calculating Volumes With the Volumes Dashboard is what I would use for what you described.

For capacity of a stormwater area I'd determine the overflow elevation and add a contour at that elevation, then extract it to the drawing as a boundary to use with the Volumes Dashboard to get a quick accurate volume.