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Delete Triangles vs adding Outer Boundary to eliminate them. Pros/Cons?

35 REPLIES 35
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Message 1 of 36
doni49
2008 Views, 35 Replies

Delete Triangles vs adding Outer Boundary to eliminate them. Pros/Cons?

When cleaning up a surface, I've always created an Outer Boundary to define the surface limits so that the triangles wouldn't go where I didn't want them.

 

I'm trying prepping in hopes of sitting for my Autodesk Civil 3d Certification exam at AU.  The chapter I'm currently reading through talks about deleting triangles from the surface.

 

So now I'm wondering about the pros and cons of both methods.

 

Any advice would be greatly appreciated.

 

TIA!



Don Ireland
Engineering Design Technician




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35 REPLIES 35
Message 21 of 36
troma
in reply to: doni49

Good catch. I skimmed over that too fast. I guess the blog is just wrong.

Mark Green

Working on Civil 3D in Canada

Message 22 of 36
Jeff_M
in reply to: doni49

The help file says that the max angle is only applied to exterior triangles:

Specifies whether the triangles on the exterior border of the TIN will be assessed to see if they exceed the Maximum Angle Between Adjacent TIN Lines (CreateSurface andVolumesDashboard command settings only). If Use Maximum Angle is set to Yes, triangles on the exterior border of the TIN are assessed. A triangle is removed from the TIN if the angle which faces to the border edge exceeds the maximum angle specified.

 

So perhaps the person who commented on the blog post was mistaken?

Jeff_M, also a frequent Swamper
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Message 23 of 36
doni49
in reply to: troma


@troma wrote:
I skimmed over that too fast.

I've done that more often than I care to admit.Smiley Frustrated



Don Ireland
Engineering Design Technician




If a reply solves your issue, please remember to click on "Accept as Solution". This will help other users looking to solve a similar issue. Thank you.


Please do not send a PM asking for assistance. That's what the forums are for. This allows everyone to benefit from the question asked and the answers given.

Message 24 of 36
doni49
in reply to: Jeff_M


@Jeff_M wrote:

The help file says that the max angle is only applied to exterior triangles:

Specifies whether the triangles on the exterior border of the TIN will be assessed to see if they exceed the Maximum Angle Between Adjacent TIN Lines (CreateSurface andVolumesDashboard command settings only). If Use Maximum Angle is set to Yes, triangles on the exterior border of the TIN are assessed. A triangle is removed from the TIN if the angle which faces to the border edge exceeds the maximum angle specified.

 

So perhaps the person who commented on the blog post was mistaken?


And that assumes that the help file is correct AND that there's not some kind of bug that's causing interior triangles to get removed.  I guess you're right Autodesk's Help files are ALWAYS correct and the software is completely bug free.

 

Ok - now I'll take my tongue out of my cheek.  Smiley Wink

 

EDIT:  Jeff, after re-reading this post, I wanted to make it clear:  I have nothing but the utmost of respect for you and your posts.  The above was completely tongue-in-cheek and meant as sarcasm about the poor help files and the level of bugs we seem to experience.



Don Ireland
Engineering Design Technician




If a reply solves your issue, please remember to click on "Accept as Solution". This will help other users looking to solve a similar issue. Thank you.


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Message 25 of 36
troma
in reply to: Jeff_M

Perhaps.  There could have been something else causing the hole in his surface.

 

But Peter seemed to agree with that poster:

 


@peterfunkautodesk wrote:

...

This can remove interior and exterior triangles.

...



Mark Green

Working on Civil 3D in Canada

Message 26 of 36
cbaildon001
in reply to: troma

I was the commenter in that blog and at the time I was using 2013 (no service packs). I also sent off a support request to Autodesk to resolve the issue, they did respond to me and from memory they said that the maximum triangle angle option was designed for use with corridor or grading surfaces (which don't suffer from skinny interior triangles like topographical survey can). Don't quote me on this as don't have any emails or forum posts to support this.

 

I have just retested this in 2013 and in 2014 and Civil3D appears to be doing a pretty good job of not removing interior triangles.

 

So either I was wrong in my initial assesment of this function in 2013 or it was improved in one of the service packs. If they did change it they never told me. I'm very sure it wasn't working as I would have liked for surveying but now it appears to be.

 

As far as this thread goes. I use (1) maximum triangle length (check for holes), (2) delete triangle lines, (3) extract boundary as polyline and apply as a boundary, (4) delete my delete line edits.

 

Regards

Caleb Baildon
Senior Surveyor
Opus International Consultants Ltd
Wellington, New Zealand
Civil3D 2015 - Windows10
Message 27 of 36
neilyj666
in reply to: cbaildon001

this is my typical workflow and it works well for me

neilyj (No connection with Autodesk other than using the products in the real world)
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Message 28 of 36
cbaildon001
in reply to: cbaildon001

I have been trying Maximum triangle angle out some more and one more thing I would like it to do, is to respect breaklines. When I include a survey figure as a breakline I don't want this option to remove triangles past any breaklines. See attatched image - surface gets trimmed inside the fenceline I surveyed.

Caleb Baildon
Senior Surveyor
Opus International Consultants Ltd
Wellington, New Zealand
Civil3D 2015 - Windows10
Message 29 of 36
neilyj666
in reply to: cbaildon001

Don't believe the Max triangle method differentiates between breaklines and non breaklines - it works purely on triangle length; try reducing the max length value. As mentioned in other posts, you can get the trianglulation almost (or exactly if you are lucky) correct, extract the boundary, convert to 2d Poly and edit/add vertices along the boundary as required. Remove all triangle edits from surface definition and then add the 2D poly as an outer boundary.

The definitive guide to this process is demonstrated by the late Sinc (one of the original Civil 3D gurus) in the following video http://www.quuxsoft.com/videos/AddBoundaryToSurface.aspx

neilyj (No connection with Autodesk other than using the products in the real world)
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Message 30 of 36
Nik-D
in reply to: doni49

Here's my take on the add boundary, delete triangle line thing:

 

I have found in the past that if I use a boundary for the surface that the boundary is not always stable. What I mean is that once I have applied the boundary as an OUTER boundary, every now and then the triangles outside the boundary reappear and I have to delete the boundary and then reapply it. If I delete the triangles outside the boundary then they stay deleted and the boundary is stable.

 

These days my preference is to use the original topo survey provided by the surveyor and boundary from the architects and create my surface (deleting any spurious points with 0.00 elevation). I then DREF or XML the surface into the drawing I want to use. The drawing is more stable and runs quicker.

 

I also normally set up 2 separate drawings with a 2D boundary and a 3D boundary in them so I can import as required.

Message 31 of 36
ian_mcgregor
in reply to: troma

Hi

 

Good discussion!

 

I'd like to confirm a couple of points.

 

1) the max angle feature was designed to and should only be removing EXTERIOR triangles. If you have a data set that shows otherwise please submit it on a service ticket.

 

2) this feature should be respecting exterior breaklines/feature lines/ survey features and is the subject of a defect I recently submitted.



Ian McGregor
BIM Technical Consulting Manager
Autodesk Customer Success EMEA
Autodesk, Inc.

Message 32 of 36
dgordon
in reply to: Nik-D

in 2011 you can just move the boundary down on the list to the bottom and it will fix the boundary stability problem you mention. no need to remove and re-add anymore.
Dan

Civil 3D 2013
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Dell T5500
www.preinnewhof.com
Message 33 of 36
rendarin
in reply to: doni49

Everything seems pretty wrapped up, however I would like to add that I find just adding an outer boundary is the simplest way of making sure the generated surface stays within the available data set, and doesn't triangulate between points where it shouldn't.  As mentioned above, when when adding additional data, the boundary can be moved down in the build list so it's added last.

 

Whereas when deleting lines, after a lot of deletions and manipulations its quite hard to keep track as to which line was where; this became a problem for me before when I deleted lines and then had to add additional data to the surface because some of the triangulation wasn't working out correctly because of the deleted lines.

Message 34 of 36
cbaildon001
in reply to: ian_mcgregor

Hi Ian

Here is a post that I started, where a comment from El_nath seems to indicate that the Maximum angle option was introduced for the purpose of being able to add the boundary of one surface to be hide boundary on another surface. This was disigned to work with corridor surfaces so you could hide the portion of the EG surface where the corridor is - I don't believe it was originally designed to work with survey surfaces.

 

http://forums.autodesk.com/t5/AutoCAD-Civil-3D-Wishes/Shrinkwrap-boundary-for-survey-surfaces/td-p/3...

 

I have recently tried out the maximum triagle option and it is still not perfect. As the attachements show there are still a couple of holes in the surface and it ignores some breakline segments. But I still beleive it is a big improvement on where it was when first introduced, and if it does not work perfectly it can still be used to create a boundary that is almost there and then just needs a couple of edits.

 

Regards

Caleb Baildon
Senior Surveyor
Opus International Consultants Ltd
Wellington, New Zealand
Civil3D 2015 - Windows10
Message 35 of 36

The max angle option was added to clean up the triangles at the edge of any surface. For the corridor surfaces, typically those are pretty clean already because feature lines are used to generate the boundary.

 

Regards,

 

Peter Funk

Autodesk, Inc.



Peter Funk
Autodesk, Inc.

Message 36 of 36
ksorsby
in reply to: peterfunkautodesk

IMO, the only way of doing it simply and reliably is with outer or dataclip boundaries, as either polylines or feature lines, and then be careful as to the placing of the boundary in the definition list.

Delete lines are fine for very minor or temporary edits but you'll get plenty of triangles re-appearing later if you end up performing more functions or edits on the surface. And then good luck finding the edits you need to reinstate or delete.

 

Kevin

 

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