topic Re: Varying offset from Feature in Civil 3D Forum

Varying offset from Feature

654work — Fri, 02 Aug 2024 19:36:03 GMT

We need to grade from top of bank to the flowline of a ditch at a 3:1 slope. The flowline will very in slope and we know the elevations at specific intervals along the flowline. I thought C3D had a grading tool that would grade down to user input elevations along the feature line. Hopefully the attached will clarify what we are looking for. The goal is to have a feature line at the flowline.

C3D 2022

Re: Varying offset from Feature

brian.strandberg — Fri, 02 Aug 2024 19:40:03 GMT

I would start with the grading tools. You can create a grading criteria very easily to grade to surface at 3:1

Re: Varying offset from Feature

654work — Fri, 02 Aug 2024 19:54:58 GMT

@brian.strandberg, thank you for the reply. we do not want to grade to a surface, but create a second feature line. The distance the new feature line is away form the original feature line will vary, based on the elevation target. I can calc this by hand, but thought civil 3d had a way do automate this.

Re: Varying offset from Feature

Joe-Bouza — Fri, 02 Aug 2024 19:57:18 GMT

If the top of bank is known and the the flow line is known there is no grading to be done, just add the two FL to the surface.

Re: Varying offset from Feature

Joe-Bouza — Fri, 02 Aug 2024 20:00:26 GMT

Are you looking to locate the Flow line?

Re: Varying offset from Feature

Joe-Bouza — Fri, 02 Aug 2024 20:09:47 GMT

If the line are fixed the project 3:1 a distance beyond the Flow line the extract the 3:1 surface elevations to the flow line.

This may differ then your Known elevations.

Maybe you are trying to locate the flow line ? if this is the case

grade to each known elevation AT 3: 1 , Then add transition in between, since they are 3: 1 the transition will and your FL will be located

Almost forgot. to do this you answer NO when asked to apply to entire FL

Re: Varying offset from Feature

654work — Fri, 02 Aug 2024 20:19:10 GMT

@Joe-Bouza, I don't think I have explained this well. Hopefully this will clear it up some. The top of bank is known and specific elevations along the flow line are known, the slope of the the channel varies. We can calc the location of the flow line through curves down from the bank, but hoped C3D would generate this for us instead. If the top of bank was a straight line, projecting to the flow line could be quickly done, but the channel is several miles long and meanders back and forth. Also as the hydraulic model is updated, the elevations may change.

Re: Varying offset from Feature

654work — Fri, 02 Aug 2024 20:21:20 GMT

How do you add the transitions? That is the part I'm missing.

Re: Varying offset from Feature

Joe-Bouza — Fri, 02 Aug 2024 21:40:23 GMT

this is the part I dont get. If you know the elevation of the channel and the top of bank is fixed, the slope is what it is

anyway, the green lines are the known channel ele at 3:1, the yellow is the fixed top of bank FL. after you place the grading slivers, then in the grading tool bar drop down pick transition and pick the top of bank FL between the slivers

Re: Varying offset from Feature

Joe-Bouza — Fri, 02 Aug 2024 21:44:47 GMT

Is the flow line in a constant position?

Re: Varying offset from Feature

brian.strandberg — Fri, 02 Aug 2024 21:58:00 GMT

If you can share the drawing that will probably help a ton. Thanks.

Re: Varying offset from Feature

Jeew-m — Sat, 03 Aug 2024 10:58:37 GMT

Hi,

If I understand you correctly this is what I do.

1. Import your flow line points through a point file and add it to a point group. (If you can use dynamo that would be great)

2. Offsett your flow line polyline either side (say 1m)

3. Convert the two lines to feature lines at an elevation you like. These are dummy feature for our work.

4. Create a surface and add the two FL as breaklines

5. Then add the point group to the surface. Now you will have the flowline elevations on the surface

6. Convert the flow line polyline to a feature line. Get the elevations from the surface but avoid adding elevation points at intermediate break points and set relative elevation to 0.

7. Now when the elevations of the flow line change as a result of hydrological reasons, remove old points and add the new points to the same point group. If the changes are minimal you can manually update the points.

8. This will update the surface and ultimately the flow line feature line because it has relative elevations to the surface.

Re: Varying offset from Feature

chriscowgill7373 — Sat, 10 Aug 2024 20:23:30 GMT

Based on your description, you want to grade to a feature that has a varying offset and elevation. This, unfortunately, (or fortunately, depending on how you feel about grading objects) cannot be done with a grading object. You can do it with a corridor, using an assembly that uses the link slope to elevation generic link.

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 15:06:52 GMT

@chriscowgill7373, please correct me if I'm wrong, but the linkslopetoelevation subassembly will not create the flowline. We would need to hand calculate the flowline and create a featureline, the set the target for the subassembly.

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 15:57:20 GMT

@Jeew-m, I may be missing something from your suggestion. The flowlines horizontal location is not know, without doing hand calculations through the bends. The flowline horizontal location is what we are trying to automate creation of. With the horizontal location, the surface would be quick to create. The way I understand your suggestion is I would need to start with the flowline, then create the surface based on the points and the horizontal location of the flowline. If I'm missing something from your suggestion, please let me know.

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 15:59:14 GMT

@Joe-Bouza, no the flowline bends horizontally in several places. The top of bank varies in elevation too.

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 16:03:23 GMT

@brian.strandberg, I will try to remove certain information from the file and share, but not certain I will be able to. This is not my project, someone else in the office is working on it and we are trying to come up with a solution.

Re: Varying offset from Feature

Joe-Bouza — Mon, 12 Aug 2024 16:24:02 GMT

Pardon, that wasn't what I meant.

If you are looking to locate it, then there is a bit more to do.

Make a temp grading and surface from the top of bank., set the tessellation to something reasonable, and grade at slope for arbitrary length beyond where the flow line is expected.

the feature line for the flowline is initially placed with the known elevation snapped to the the tessellation ray. have a Feature line label style that displays vertex and slope. each vertex coincides with a ray. anywhere along the ray is 3:1 , grip edit the unknowns to a ray until the flowline slope is satisfied.

Not perfect but you will get what you need in relatively short order

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 18:18:11 GMT

@Joe-Bouza, I tried the transition with two elevations and 3:1 slope, but it does not produce the grading object.

Re: Varying offset from Feature

654work — Mon, 12 Aug 2024 18:20:18 GMT

@Joe-Bouza, ok, I get what you are saying