AutoCAD Civil 3D General Discussion

AutoCAD Civil 3D General Discussion

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nickpascoe
Posts: 1
Registered: ‎10-13-2011
Message 1 of 8 (239 Views)

Creating a true surface, gaps and all

239 Views, 7 Replies
12-11-2012 02:53 AM

Good Morning,

 

I was hoping that someone could help.

 

I have received some sendimentary data of a seabed. I also have other geological layers the sit beneath (all in XYZ format). I have created point clouds using this data and would like to create a surface in order to use the elevational banding to represent thickness. Here lies the problem.

 

When creating a surface from the point cloud (whole extent), C3D seems to fill in gaps in the data. Is there a way that C3D can create a true representation without all the lines joining parts up? I know that I can edit the surface by deleting lines but this is very time consuming and I'm wondering if there is an easier way to do this. This problem isn't exclusive to point clouds either, as it does the same when adding points to a new surface.

 

I have attached a couple of screenshots. The first shows a Point Cloud with colours showing the desired effect. Unfortunately C3D doesn't allow me to print this. The second image shows how the surface looks when created.

 

Any help would be greatly appreciated!

pc.jpgsf.jpg

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neilyj
Posts: 3,789
Registered: ‎08-01-2008
Message 2 of 8 (229 Views)

Re: Creating a true surface, gaps and all

12-11-2012 04:22 AM in reply to: nickpascoe

This behaviour is exactly as intended and you must add boundaries to restrict the triangulation formation.

 

If you have 2013 you could force a maximum triangle side length constraint which would go some way to solving the problem

neilyj
(No connection with Autodesk other than using the products in the real world)


IDSP Premium 2015 (mainly Civil 3D 2015 UKIE & Infraworks with some limited 3ds Max Design)
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Joe-Bouza
Posts: 4,966
Registered: ‎12-15-2008
Message 3 of 8 (226 Views)

Re: Creating a true surface, gaps and all

12-11-2012 04:30 AM in reply to: neilyj

Ditto, and max triangle is in lower versions as well.

 

Boundaries and breaklines are a very imprtant step to modeling a surface. I've been banging my head against the wall trying to convince our users that you cannot only use points to get the correct model.

 

I'm not big on ruminating about LDD commands but it used to have a command to draw boundary around points. something like that would be helpful

 

Thank you

Joseph D. Bouza, P.E. (one of 'THOSE' People) Civil 3D 2012 & 2013
HP Z210 Workstation
Intel Xeon CPU E31240 @ 3.30 Hz
12 GB Ram


Note: Its all Resistentialism, so keep calm and carry on

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neilyj
Posts: 3,789
Registered: ‎08-01-2008
Message 4 of 8 (206 Views)

Re: Creating a true surface, gaps and all

12-11-2012 05:22 AM in reply to: nickpascoe

Joe is correct - I meant to say the maximum TIN angle rather the length:smileyembarrassed: I've not tried it but may work.

 

Some other discussion on this topic http://forums.autodesk.com/t5/AutoCAD-Civil-3D/Shrinkwrap-Cogo-Points/td-p/3189870/page/2#.UMcy4nckT...

neilyj
(No connection with Autodesk other than using the products in the real world)


IDSP Premium 2015 (mainly Civil 3D 2015 UKIE & Infraworks with some limited 3ds Max Design)
Win 7 Pro x64, 240Gb SSD, 1Tb HDD
32Gb Ram Intel Xeon CPU E5-2650 v2 @ 2.6GHz (32 CPUs), ~2.6GHz
NVIDIA Quadro K4000, Dual 27" Monitor, Dell T5610
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Joe-Bouza
Posts: 4,966
Registered: ‎12-15-2008
Message 5 of 8 (199 Views)

Re: Creating a true surface, gaps and all

12-11-2012 05:35 AM in reply to: nickpascoe

Although the max triangle works you should use it with caution and scrutiny. Setting a max length my take out unexpected data. Review the finished triangles, thats all. Displaying 2d solids can quickly determine if you have unwanted holes

Thank you

Joseph D. Bouza, P.E. (one of 'THOSE' People) Civil 3D 2012 & 2013
HP Z210 Workstation
Intel Xeon CPU E31240 @ 3.30 Hz
12 GB Ram


Note: Its all Resistentialism, so keep calm and carry on

64 Bit Win7 OS
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neilyj
Posts: 3,789
Registered: ‎08-01-2008
Message 6 of 8 (195 Views)

Re: Creating a true surface, gaps and all

12-11-2012 05:41 AM in reply to: Joe-Bouza

Absolutely - you will in all probability have to Pan and Zoom around the boundaries to ensure that the DTM is correctly formed however if the area is very large and dpending on the accuracy you require you may be able to afford to be a little less diligent in tweaking the boundary.

 

I'd probably use the max triangle length method and extract the boundary(s), flatten and add back as a boundary, then add vertices as required to fix any errors.

 

There isn't a magic cure all for this one unfortunately

neilyj
(No connection with Autodesk other than using the products in the real world)


IDSP Premium 2015 (mainly Civil 3D 2015 UKIE & Infraworks with some limited 3ds Max Design)
Win 7 Pro x64, 240Gb SSD, 1Tb HDD
32Gb Ram Intel Xeon CPU E5-2650 v2 @ 2.6GHz (32 CPUs), ~2.6GHz
NVIDIA Quadro K4000, Dual 27" Monitor, Dell T5610
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jmayo
Posts: 2,872
Registered: ‎11-13-2006
Message 7 of 8 (183 Views)

Re: Creating a true surface, gaps and all

12-11-2012 06:53 AM in reply to: nickpascoe

If the max triangle length doesn't get what you need or it creates more work with surface edits try boundaries.

 

Add the points to a single surface. Draw a large rectangle around the entire data set. Add this rectangle to the surface as a 'hide' boundary. Create and select the inner pline boundaries for the areas to be shown. Add these to the surface as 'show' boundaries. Now take plines for the holes and add them to the surface as hidden boundaries. Note that if you select multiple plines before issuing the Add Boundaries command, you can define multiple boundaries in one shot.

 

Also note that your surafce definition requires that these boundaries remain at the bottom of the surface definition and must maintain the order they were defined in. 1 hides the entire site, 2 shows the areas in question and the 3rd set will hide the holes.

John Mayo, PE
IDSP 2014
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64 GB RAM, Quadro K4000 (x2)
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jmayo
Posts: 2,872
Registered: ‎11-13-2006
Message 8 of 8 (180 Views)

Re: Creating a true surface, gaps and all

12-11-2012 06:59 AM in reply to: jmayo

Here's an example of that method used for flooplain (light blue) calcs. I use surfaces for the woods (green) and banks (dark blue) to delineate these areas in section and/or profile.

John Mayo, PE
IDSP 2014
Win 7 64, Xeon ES165@3.2Ghz,
64 GB RAM, Quadro K4000 (x2)
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