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Offset a surface

35 REPLIES 35
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Message 1 of 36
Kyle-Evans
1907 Views, 35 Replies

Offset a surface

Hey guys,
I have a interesting question here, I know there is a way to raise/lower a surface, but is there a way to offset a surface basically 1m (to make it easy) perpindicular to all grades? Because when you raise/lower a surface, if you have a 3:1 slope, it will raise/lower it verticall 1m or so, but then the perpindicular distance between the 2 surfaces is less then 1m.

If anyone has any ideas or any insight, that would be great.

Thanks
35 REPLIES 35
Message 2 of 36
Anonymous
in reply to: Kyle-Evans

Hi,

Fact of life. The perpendicular distance between the surfaces will only
be 1m when the surface is horizontal. Everywhere else it will vary. It
can also vary depending on which surface you start at and then go
perpendicular to the other.



On 8/04/2010 12:11 PM, Sindarin wrote:
> Hey guys,
> I have a interesting question here, I know there is a way to raise/lower
> a surface, but is there a way to offset a surface basically 1m (to make
> it easy) perpindicular to all grades? Because when you raise/lower a
> surface, if you have a 3:1 slope, it will raise/lower it verticall 1m or
> so, but then the perpindicular distance between the 2 surfaces is less
> then 1m.
>
> If anyone has any ideas or any insight, that would be great.
>
> Thanks

--

Regards

Laurie Comerford
Message 3 of 36
Kyle-Evans
in reply to: Kyle-Evans

Hey Laurie,

I was asking if there was a way to offset the whole surface so everything is 1m perpindicular distance
Message 4 of 36
corboto
in reply to: Kyle-Evans

I had this same question a while ago. The consensus was it can't be done in Civil 3d. I'm not that familiar with other Autodesk software but it seems to me that somehow this should be possible. I tried making my surface a solid using the triangles and thought I could import that into another piece of software and offset (or extrude?) it, but I never found anything that could do this. I called our local Autodesk salesman and he didn't have any ideas either.

To make a long story short, I ended up offsetting my surface manually; which, in my case, wasn't too hard, it was just time-consuming.

Here's the old thread just in case it helps you some. I'd love to know if you find out anything. Good luck.
http://discussion.autodesk.com/forums/thread.jspa?messageID=6227142ӆ
Message 5 of 36
wouterb2
in reply to: Kyle-Evans

I was researching the same question...
it seems they have done it in civil3d 2011 with the command SURFOFFSET

i don't have 2011 yet so still looking...
Message 6 of 36
Anonymous
in reply to: Kyle-Evans

Hi Sindarin,

Whoops, I did misread your post.

The discussion referred to by corbittshoffer and in particular the post
by Allan Jessup do describe how you can do it.

Allan's lisp program to offset the 3D faces is a start and you could
just build a model from the offset faces accepting that there would be
linear interpolations between triangle edges of the offset triangles.

Where the offsets are convex this would be an acceptable model.
Where the offsets are concave (ie at a valley or ridge line depending on
which way you are offsetting) you would have errors and you would have
to know your site and the level of error acceptability to determine what
extra steps to take to reduce the errors.


A viable manual method to improve the model would be to:
Use a display of the watershed boundaries to guide you as to ridge line
locations, or mirror image the surface and display watershed boundaries
of the mirrored surface to see the valleys as needed depending on
whether you are offsetting upwards or downwards.

In the concave situation, you could transform the crossing triangles to
regions and explode them back to 3D lines. Then trim the lines back to
the watershed lines and delete the 3D lines which are on the wrong side
of the watershed boundary. Finally build the new surface from the
trimmed 3D lines and the other triangles.

Alternatively you would need to follow the theory in the PDF file Allan
referenced and program the required result.

Regards

Laurie Comerford

On 8/04/2010 11:53 PM, Sindarin wrote:
> Hey Laurie,
>
> I was asking if there was a way to offset the whole surface so
> everything is 1m perpindicular distance
Message 7 of 36
AllenJessup
in reply to: Kyle-Evans

Unfortunately that looks like it's basic AutoCAD command and will work on AutoCAD 3D surfaces not Civil 3D Surfaces.
Allen


Allen Jessup
Engineering Specialist / CAD Manager

Message 8 of 36
corboto
in reply to: Kyle-Evans

So you would have to take the C3D surface triangles and convert them to an autocad surface and then use the surfoffset command? Is that the easiest way to do this?
Message 9 of 36
AllenJessup
in reply to: Kyle-Evans

Sounds right and I don't know any other way to do it. But I don't have 2011 installed yet so I can't say for sure how well it will work. If you try it, let us know.
Allen


Allen Jessup
Engineering Specialist / CAD Manager

Message 10 of 36
Kyle-Evans
in reply to: Kyle-Evans

The way that I ended up accomplishing this was to take the feature lines used to make the surface and do a stepped offset of them. I am looking for a more automated way though.
Message 11 of 36
ArchD
in reply to: Kyle-Evans

I searched for the solution to this, but I found this thread, and sadly, there wasn't much in the way of a solution.

 

After playing around with a few things, I ended up taking the existing surface and displayed nothing but triangles, and extracted them.

 

I copied the triangles into a new drawing, and extruded them 2 feet. This gave me a 3D solid with the top face 2 feet offest from the orginal triangles normals.

 

I switched to conceptual view style and exploded the 3D solids giving me regions.

 

I then selected all the upper regions (this was the most tedious part), then hid them using object isolation. What was left was the bottom regions (the triangles I originally started out with), and the sides. I deleted them and ended object isolation mode so that all I was left with was the top regions.

 

I then switched back to 2D mode and exploded the regions, and converted the lines to polylines. I then created a surface and added these polylines as contours. Once the surface was created with the polylines as its definition, I showed nothing but points in the surface style and extracted them.

 

After the points were extracted, I was left with a number of point clusters very close together due to the triangles being extracted perpenducular to their normals. I used MAPCLEAN to snap clustered nodes, and used a tolerance value big enough to cover a cluster. This left me with one point per cluster.

 

Once I had the points, I converted those into COGO points, then exported them to a point data file (so I didn't have to go through the headache of recreating this again).

 

In a new drawing I created a surface out of this point file and saved it as a data shortcut.

 

Once it was all done and over, I cut cross sections showing the original surface and the new surface, and they came out nearly perfect. You may need to swap alot of edges to make it correct. When swapping the edges, it may be easier to create a reference to the original surface so that you can make sure the contours match up (of course they will be a bit staggered along slopes).

 

I know this is an old thread, but if someone Googles it like I did, hopefully this will help out a bit.

Archie Dodge
Applications Expert - Infrastructure Solutions Division
IMAGINiT Technologies
Message 12 of 36
neilyj666
in reply to: ArchD

Good solution - but you must have far too much time on your hands....Smiley Wink

neilyj (No connection with Autodesk other than using the products in the real world)
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Message 13 of 36
ArchD
in reply to: Kyle-Evans

Thanks, it's not a perfect solution, but it's really close!

Like my signature says, I'm still a junior CAD technician. They pay me by the hour. 😉
Archie Dodge
Applications Expert - Infrastructure Solutions Division
IMAGINiT Technologies
Message 14 of 36
neilyj666
in reply to: ArchD


@ArchD wrote:
They pay me by the hour. 😉


You've earned your money for this then.....

neilyj (No connection with Autodesk other than using the products in the real world)
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Win 11 Pro x64, 1Tb Primary SSD, 1Tb Secondary SSD
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Message 15 of 36
AllenJessup
in reply to: ArchD

Very nice solution. Using Mapclean was the way to clean up the clustered points. If I'd thought of that I could have done it with my original lisp. It created the points so all that was needed was to clean them up.

 

Allen



Allen Jessup
Engineering Specialist / CAD Manager

Message 16 of 36
ArchD
in reply to: ArchD

Allen, If you update your lisp, I would be very interested in it. Anything to automate this, especially the region selecting would be extremely valueble.

Archie Dodge
Applications Expert - Infrastructure Solutions Division
IMAGINiT Technologies
Message 17 of 36
AllenJessup
in reply to: ArchD

I'll see what I can do. As I've said in the other threads, offsetting surfaces isn't something I've had to do. It was just an exercise in using lisp and the Geometry Calculator. I haven't done any lisp programming in years. I've never tried my lisp in Civil 3D or in any recent version of Autocad.

 

What the original lisp would do is to take 3DFaces and create points at a normal vector to the vertices. So if I can get it to run in C3D I might get you to the step where you have points. Then you could use Mapclean. I'll see if I can get to it later in the week.

 

For anyone who does a lot of surface offsetting. I know that QuickSurf used to be able to do this. I haven't use this software in over 20 years. So I'm not up on it's current capabilities.

 

Allen



Allen Jessup
Engineering Specialist / CAD Manager

Message 18 of 36
neilyj666
in reply to: AllenJessup

This really begs the question - why does this functionality not exist in the basic C3D product?? Lack of demand, too difficult to program??

 

The main application would be for the design of landfill cells, dams, flood barriers etc all of which are viable markets for C3D. Someone will no doubt chime in and say the Sub Assembly Composer could do this but not everything lends iself to corridor modeling...!!

neilyj (No connection with Autodesk other than using the products in the real world)
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Message 19 of 36
ArchD
in reply to: AllenJessup

What the original lisp does sounds like it saves a ton of work. Basically cutting out the extruding, selecting regions, converting them to poly lines, adding those to a surface and then extracting points could all be skipped. So basically most of the work. 🙂

 

Sounds like no changes are needed to the orginal. Can't wait to try it. Is there a download link or the code I can get from you?

 

Thanks for your help on something you don't even have a use for. Much appreciated.

 

 

Neilyj

Everything you said is accurate to my situation. I create very complex grading designs for fertilizer companys waste, as well as power plants ash piles. When you need to build a ramp up the side of a gypsum stack, corridors just don't work as you would like them to. Most of my work ends up being feature lines with grading and infills.

 

On this particular project, I'm working on a pond that was built about 10 years back and we need to take what is existing and add a 2 foot cover to it. No easy way to do that accurately.

Archie Dodge
Applications Expert - Infrastructure Solutions Division
IMAGINiT Technologies
Message 20 of 36
AllenJessup
in reply to: ArchD

I'll attach the original files. I just did a quick test and it does not work in C3D 2012. If you want to go ahead with this right away. You might want to ask if anyone in the customization group could help. I'm very rusty at this.

 

Allen



Allen Jessup
Engineering Specialist / CAD Manager

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