Non-Destructive Breaklines

[Pointdump]

Little things bother me. I can't just accept something cause it's the way it is. I like to know the reasoning behind it.

Case in point:

Why does the check box say "Non-destructive breakline?" Why doesn't it say, "Erase tin lines that cross boundary?" I doesn't seem to have anything to do with breaklines. Or am I wrong on that one?

While I'm on a roll, double negatives send me into a tailspin. Like "Disable description keys", True or False. Huh? Why not just say, "Description Keys", on or off?

Dave

[sboon · Accepted solution]

This thread might help to explain it.  For a boundary it's all about whether or not you want to use the TIN data up to the boundary, or you want to completely remove the TIN lines which cross the boundary.  Looking at your example I can see some TIN lines on the right side which I suspect are not representative of the true surface where they cross the boundary.  A non-destructive boundary across that side would be incorrect.

Steve
Please use the Accept as Solution or Kudo buttons when appropriate

[Pointdump]

Thanks for your response, Steve, and for the thread link that I will brood over in the still watches of the night.
I still don't understand how the boundary becomes a breakline, or what is spared destruction by a non-destructive breakline, or what is destroyed by a destructive breakline?

My PNG above is from a lesson I'm working on in Rick Ellis's book "A Practical Guide to AutoCAD Civil 3D 2014." An excellent book, by the way.

He writes:
"Enabling the Non-destructive breaklines option trims the surface at the boundary while disabling it erases any surface lines that cross the boundary. This option is useful when you have good surface data on both sides of the boundary and are using the boundary to limit the extents of the surface. It is typically not used for outer boundaries."

Oh, and Steve, your post says "Edited". How do you do that? I've got a typo in my top post that I'd like to correct.

Dave

[neilyj666 · Accepted solution]

you can, for example, sling a rough 2d poly around the boundary in the screenshot, add as destructive and remove the incorrect triangles. there are of course other (better?) ways to do this, I only cite this as an example of use.

[sboon]

Rick's description is accurate.  The decision about what type of boundary to use depends on what data you have and how you want to use it.

For example I have a surface built from a Lidar data tile.  My area of interest is relatively small but the Lidar covers much more area and I know that all of it is good quality.  I can run a polyline that encloses what I need and use a non-destructive boundary because I trust that the TIN lines crossing it are all good.

On another site I have data from a topographical survey of a winding creek channel.  I know that the limits of the field work are at the treelines on either side of the channel.  In that case I have no faith in any TIN lines outside of those treelines so I am going to draw a polyline running from point to point along the actual limits of the work.  I'm going to offset that polyline slightly outside of the survey and then make it my destructive boundary. 

Steve
Please use the Accept as Solution or Kudo buttons when appropriate

PS: If you check the options dropdown at the top right of your post then Edit may be listed.  Please note however that there is a time limit for this option.

[Pointdump]

Neilyj and Steve,

OK, I get it now. A Destructive Breakline, or Polyline, or Feature Line, will erase (Destroy) any Tin Lines that try to cross, and a Non-Destructive Breakline will just trim (Not Destroy) the Tin Lines.

Thanks for helping me to understand.

Steve, that Edit time limit must be pretty short. After I hit the gas on this, I'll check to see if "Edit" is in the options.

Update: Yes, Edit works but for a short time.

Dave

[neilyj666]

The edit time is 30 mins I believe, after which time the post is locked

[troma]

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@Pointdump wrote:

Little things bother me. I can't just accept something cause it's the way it is. I like to know the reasoning behind it....

Dave

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A good way to be in my opinion.  Always better to ask questions.

Personally I hate the terms 'destructive' and 'non-destructive'.  After the boundary is added, it is termed "Trim"—Yes or No.  Why the inconsistency?

Totally with you on the double negatives too.

PS. I belive a post is also locked for editing if someone replies to it.

[Pointdump]

Thanks Troma. 

Confucius put it well:

"If concepts are not clear, words do not fit. If words do not fit, the day's work cannot be accomplished."

Analects of Confucius, XIII, 3

Dave