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Subtract one surface from another.

9 REPLIES 9
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Message 1 of 10
CAD_Avatar
7768 Views, 9 Replies

Subtract one surface from another.

Hello all,

I am in need of subtracting Surface A from Surface B to display the surface intersections between the two. I have a geological top of clay surface and a bottom of clay surface where the bottom intersects with the top thus showing holes in a geological clay layer. I am wanting to know if Civil 3D supports the subtracting of two surfaces.

Thank you!
9 REPLIES 9
Message 2 of 10
Anonymous
in reply to: CAD_Avatar

brian_ranstead@urscorp.com wrote:

> I am in need of subtracting Surface A from Surface B to display the
> surface intersections between the two. I have a geological top of
> clay surface and a bottom of clay surface where the bottom intersects
> with the top thus showing holes in a geological clay layer. I am
> wanting to know if Civil 3D supports the subtracting of two surfaces.

Don't claim to be an expert, but you should be able to create a 'Volume
Surface', using care in specifying the order of base/compare surfaces.

Then contour elevation 0.0.

Terry
--
Never start any job without the right tools!
AutoCAD Add-on Tools at http://www.dotsoft.com
Message 3 of 10
BrianHailey
in reply to: CAD_Avatar

Terry, if you are just trying to get the intersection of the two surfaces, the order they are added (base vs. comparison) doesn't matter.

Brian Hailey
http://www.cad-1.com
http://www.AtYourDeskTraining.com

Brian J. Hailey, P.E.



GEI Consultants
My Civil 3D Blog

Message 4 of 10
Anonymous
in reply to: CAD_Avatar

BrianHailey wrote:

> Terry, if you are just trying to get the intersection of the two
> surfaces, the order they are added (base vs. comparison) doesn't
> matter.

True, but todays 'just' is often tomorrows 'first of many', so might as
well build it right today.

Terry
--
Never start any job without the right tools!
AutoCAD Add-on Tools at http://www.dotsoft.com
Message 5 of 10
eng_samuka
in reply to: Anonymous

Terry

When i do what you say, the result volume surface is in the wrong elevation.

Example: my surface "1" is in (+-) elevation 235.600 and my surface "2" starts from 235.850 to 235.450 (it's like a cup), when i do the volume surface, the result goes to elevation 0.0 (+-), and when i do contour elevation 0.0, it gives me the interserction but in the wrong elevation! how do i put this in the right elevation? because what i want is the (surface 1)-(surface 2)

 

thanks for your time

 

Ivo Costa

Message 6 of 10
mathewkol
in reply to: CAD_Avatar

The elevation you're seeing is the difference in elevation between the two surface; surf 1 minus surf 2. This is what it seems like you asked for. So you have your contour line representing where they intersect and all you need now is its elevation to match the surfaces?

Turn it into a feature line and use the surface from elevation tool.
Matt Kolberg
SolidCAD Professional Services
http://www.solidcad.ca /
Message 7 of 10
BrianHailey
in reply to: mathewkol

If you don't have a good understanding of how Sites work within Civil 3D, I would recommend that you don't use a featureline, just use the same tool and assign the elevations to the polyline instead. If you want more inforomation on why I recommend this, check out THIS.

Brian J. Hailey, P.E.



GEI Consultants
My Civil 3D Blog

Message 8 of 10
Gran_Visir
in reply to: eng_samuka

Hello Terry

I'm experiencing the same issue and, searching the web, I've found you post
Did you find a solution? I'm still trying to have a "real" difference-surface, that means a third surface that will be the real difference between surface 1 and surface 2 at the right elevation
A sort of bolean operation we usally apply with solids, for instance

Any help?

 

Message 9 of 10
ChrisRS
in reply to: Gran_Visir

MIMUMDISTANCEBETWEENSURFACES will create 3D polyline(s) where the two surfaces intersect.

The 3D polyline(s) will be at the shared elevation of the intersecting surfaces.

I think that this is what you are looking for.

 

The zero (0) contour of a TIN Volume surface, referencing the same two surfaces will trace the same intersection, but at elevation zero (0). This is logical if you consider that a TIN Volume surface represents the elevation difference between two surface. Where the comparison surface is higher than the base surface the value is positive, indicating fill. Where the comparison surface is lower than the base surface the value is negative, indicating cut. Where the surfaces match (intersect) the value is 0. 

 

Conceptually, it may make sense to thin of a TIN volume surface as a TIN Depth or TIN Cut/Fill surface.

Christopher Stevens
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Message 10 of 10
rl_jackson
in reply to: Gran_Visir

You should probably start a new thread.... Get better response


Rick Jackson
Survey CAD Technician VI

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