Slicing multiple 3D solids using multiple surfaces

[Anonymous]

Hi Autodesk Community,

This is a first time post in this forum so hopefully I’m in the right place for some advice.

I'm using AutoCAD Civil 3D from the 2015 Education Master Suite.

I am currently working with a series of 3D solids (generated from TIN surfaces, which were in turn generated from a series of sets of 3D polyline 5m contours) which represent changes in terrain for a site covering approximately 13 sq. km. The purpose of the exercise is to extract a series of ‘blocks’ which represent the excavation that has occurred between each set of survey and the next.

Since this process is relatively heavy for the computer I am working on, what I am trying to do is slice the 3D solids (beginning with just two) using the map reference grid that I have as a set of polylines extruded vertically to a set of surfaces (pretty much projecting the map grid into 3D). The idea is that I will end up with a series of columns with two instances (3D solids) of the terrain in each column / grid cell for which I can then subtract the older terrain from the newer terrain. There are also other reasons aside from this for wanting the terrain sliced up this way.

So I know what I need to do, but I want to know if there is a more efficient way to slice two (or more) 3D solids using a set of surfaces rather than executing the SLICE command for each slicing surface. I have used some simple LSP programs for other tasks but have yet to find one along these lines, not sure if this is a possible approach?

Also, does anyone have an idea of the algorithm the SUBTRACT command uses, and how it deals with intersecting solids that flip from one solid being the surface to the other? I guess you could say “positive” and “negative” volumes.

I am happy to provide more clarification to help get my questions answered.

As a new user, any advice would be greatly appreciated!

[Anonymous]

Hello Catherine,

There is the AutoCAD Civil 3D forum that I'm sure would have more Civil minded people around.

As a relative new user of AutoCAD 2015 myself (not involved in civil work) my first thought is to suggest looking into the VIEWBASE command that would allow you to easily create multiple sections. For conducting subesquent calculations by subtraction, after creating the viewbase sections you could export the layout, then convert the sections to regions and perform the subtraction.

But I'm willing to bet Civi 3D has some more effecient tools.

[Anonymous]

Hi Patrick,

Thanks for the suggestion, I have reposted the question to the AutoCAD Civil 3D forum to see what other advice I can get.

I've had a quick look into the VIEWBASE command and at the moment it doesn't really seem to be what I'm looking for, but I'll keep it in mind to come back to if I don't find anything closer to what I'm looking for.

Thanks a  bunch!!