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Silvercloak

Mastering Surfaces - Using Breaklines

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Silvercloak

Hi folks,

 

Not sure if this has been addressed before. I can't find any information anywhere using google so...

 

I've created a surface using a points file, however I don't know how to use breaklines effectively. I suppose I should be using them for curbs, sidewalks and houses, right?

 

If I use them - do I choose standard? Wall? Non-Destructible, etc. etc.? How high? Do I use 0? Nothing I google really gives me any clarity on this. Can someone with more experience with this help at all?

 

Travis Penner

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CyberAngel

Put simply, you put a breakline wherever you need to interrupt or transition a surface. Think of the standard breakline as a hard-coded contour. Any triangle that would normally pass through that line is broken, and the line becomes a side of each of those triangles. A standard breakline is good for indicating a feature that might not otherwise show up, such as the bottom of a ditch.

 

The wall breakline actually has two lines, one low, one high. If you have a curb, for instance, you provide the lower line (the bottom of the curb) and a height, and you get a second line representing the top. Make sure you provide a tiny offset, because a zero offset forces the system to divide by zero, and that gives you weirdness.

 

The height of the "wall" depends on your needs. If you're calculating cut and fill, you need an accurate number for the volume dug out for a house. If you're only interested in contours on a plan, the height isn't important.

 

A destructive breakline, as the name indicates, cuts off any continuity in the surface. The area inside is treated as flat (if it's closed). That's the default, and that's usually what you want. A non-destructive breakline creates a border but doesn't affect the surface itself, just breaks up the triangles through which it passes.

 

The best advice I can give you is to experiment. This is one of those topics where you have to see it for yourself. Add a breakline, see what happens and whether it's what you expected, close the drawing without saving, repeat. Vary the options and the parameters.

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Silvercloak

The best advice I can give you is to experiment. This is one of those topics where you have to see it for yourself. Add a breakline, see what happens and whether it's what you expected, close the drawing without saving, repeat. Vary the options and the parameters.

 

Thanks - that helps a bit... I'll tinker when I have time and see what I can figure out.

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Silvercloak

Oh - that reminds me. I WAS tinkering a little yesterday using lines that had Z values to them from the survey. However when I turned them into breaklines, the breaklines dropped to an elevation of 0 which totally BORKED my surface. I don't know what I did wrong.

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BIGAL

It is a bit of a idiosyncrasy with CIV3d is its brealines and how difficult they made it, having been invloved in an alternative world wide Civil package it just had a simple option declare a line as a break line or not, you can turn them on or off also if you need to.

 

Anyway the way our guys got around it was by using specific field coding that was known as a breakline, Str-B-Kerb is different to Str-Kerb, isolate all the correct layers -B and they are breaklines. I dont do this part of the process but if others want more details just ask here and I will ask our guys to explain.

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CyberAngel
Oh - that reminds me. I WAS tinkering a little yesterday using lines that had Z values to them from the survey. However when I turned them into breaklines, the breaklines dropped to an elevation of 0 which totally BORKED my surface. I don't know what I did wrong.

 

Were they lines or polylines? IIRC, a polyline doesn't lose its elevation when it becomes a breakline.

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tombu
Oh - that reminds me. I WAS tinkering a little yesterday using lines that had Z values to them from the survey. However when I turned them into breaklines, the breaklines dropped to an elevation of 0 which totally BORKED my surface. I don't know what I did wrong.

 

Assuming Process Linework was checked and those "lines that had Z values to them from the survey" are Survey Figures go into your Figure Prefix Database Manager and make sure under Breakline all the figure prefixes that should be breaklines are checked. Now if you right-click Figures and click "Create breaklines…" a box pops up allowing you to Select a surface and add all those breaklines to it. After clicking OK and naming them they will be in that surfaces definition.

 

Survey figures have many advantages as they're drawn in the field by someone looking at what they're drawing. They're like a lwpolyline except they carry elevation along their path prorated between the elevation of the shots in the field making them perfect for breaklines. You simply cannot create a curved breakline with simple autocad objects.

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BIGAL
You simply cannot create a curved breakline with simple autocad objects

 

Only way is to create 3Dlines and add to surface.

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tombu
Only way is to create 3Dlines and add to surface.

 

Only works for line segments though, you simply cannot create a curved breakline with a simple AutoCAD object. A curb with three lines including the gutter for example.

 

I'm fortunate to have surveyors in the field who provide the linework for me. They also provide photos and are accessible if I have questions. I know that's not true at a lot of other offices. Qualified folk in the field are a good investment many places cheap out on. I'd be using 3Dlines if that was what I had to do as well.

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