Subtract 3D solids from Civil 3D surface

[jonessp]

The task I've been given, is to calculate the cut that would be created by various structures embeded in a surface (e.g. concrete slabs). Grading isn't an option, due to the 3D shapes of some of the structures.

I've created the existing surface in Civil 3D and was about to create all the structures as 3D solids, but before I do, I need to be sure that there is a method for subtracting one from the other!

I would then create a volume surface from the existing and the proposed.

Basically, how do you subtract 3D solids from a Civil 3D surface?

[brainman1000]

I dont believe you can do that because they are 2 different entities. You will probably need to take the volume of the 3d object and manually subtract it from the surface volume.

[sinc]

In general, 3D Solids are not used in Civil 3D in any way. (I hear this has caused some frustration among people who are trying to use C3D with Revit, because by contrast, Revit uses solids for many things.)

[brian.hailey933139]

I wrote this up when I was working for a different company:
http://cadcafe.blogspot.com/2007/04/you-want-solid-from-your-surface.html
Perhaps it could help.