Why does C3D create non-destructive points?

[srousey74V5X]

It's my first time on here, so please excuse me if I don't do things correctly.

When I create surfaces, C3D adds it's own points in certain locations. These are crosses with squares around them. I have seen where they are referred to as "non-destructive points". I work for a survey company, and I ONLY want it to interpolate between the points that the crew shoots. Often times the elevation of these square points don't make sense in comparison to the rest of the points, and thus the surface is incorrect. I have seen where they get created along boundary lines. That certainly seems to be the case for me. In my current project I have moved these boundaries to the bottom of the list under "definition" in the surface, and the points still show. WHY does C3D create points on it's own and can I stop it from doing this? How do I remove them from current surface?

I'm using Windows 10 and Civil 3d 2015

[BrianHailey]

Hi and welcome to the forums!

I'm not exactly sure which points you are referring to. Civil 3D shouldn't be adding any additional points to your surface unless you tell it to (via breakline supplementing, border as non-destructive breakline, smoothing surface, etc.). Can you share your surface here for us to look at? Zooming in on a point that you don't think should be there (perhaps draw a circle around it) will help us identify the issue.

[tcorey]

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@srousey74V5X wrote:

It's my first time on here, so please excuse me if I don't do things correctly.

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No one gets flamed on this forum. We're civil ized.  😉

Take a look at your Surface Properties, Definition tab, in the bottom section. Do you see Minimize Flat Areas? That function will add points as it tries to find area where contours/polyline have interpolated to themselves, causing flat spots. You can just uncheck that option, rebuild, see if that works for you. If it doesn't, and you want to put the setting back, just go to the dialog and turn it back on.

[AllenJessup]

They're most likely the result of non-destructive breaklines or boundaries. I don't know how to stop their creation other than not to use that type of breakline/boundary.

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@srousey74V5X wrote:

It's my first time on here, so please excuse me if I don't do things correctly.

I'm using Windows 10 and Civil 3d 2015

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Very good first post including your version and OS. If you have performance or display issues. Please include computer and graphics card specs. The [Mac]ro dropdown makes it easy to add this info without typing it our each time.

[srousey74V5X]

Attached is the drawing file.

[srousey74V5X]

I see "Use minimize flat faces". Is that what you are referring to? The value is currently set to yes. How will changing that setting affect my surface?

[srousey74V5X]

The surface had 2 different areas that were shot. I separated the 2 using an overall "Hide" boundary and 2 separate "show" boundaries to keep from interpolating from 1 area to the other. I have seen this method suggested in other forums. I don't know if that matters some how. The square points I'm asking about are occurring pretty far away from the smaller area, so I don't see that being a factor. What determines WHERE it creates these mysterious points???

[BrianHailey]

When you added the boundaries to your surface, you used the option, "Non-destructive breakline" (or something along those lines). When using that option, if a boundary line crosses a triangle, it will place a point in the surface at that spot so it has something to triangulate to. If you don't want it to triangulate to that point, don't use the non-destructive option. Not choosing non-destructive, if the boundary crosses a triangle edge, it will completely remove that triangle. In other words, the only triangles that will be displayed in your surface are the ones that are completely within the boundary. If you want the surface to go to the boundary, it needs additional point along the boundary to triangulate to.

Hope this makes sense.

[srousey74V5X]

I apologize. I notice I had turned the surface off and points off. I have attached the drawing showing the TIN and the points. When you open the drawing you should be looking at the area with the created points.

[srousey74V5X]

If you look at the recent drawing I attached, why can't it simply interpolate between the survey points that are used. The longest leg is 194'. I don't mind it interpolating that long in this example. Just let points 462 & 463 interpolate directly to point 313? Why can it not simply do that?? I went back and did the boundary deselecting the "non-destructive breakline". Then It just stopped the surface at point 461, completely ignoring points 462-464???

[AllenJessup]

I turned off your Overall Hide boundary and traced the lines in red shown below. Then I turned it back on and created the screenshot. It shows why the non-destructive points are created where they are. This is what Autodesk calls "expected behavior" The second screenshot shows how I've use the Add Line and Delete Point commands to create the interpolation you want to see.

z

One problem is that once the non-destructive points are created. They don't disappear if you uncheck the boundary.

The surface creation algorithm can only go so far. That's why we need the Surface editing tools.  

[srousey74V5X]

Thank all of you for the responses.

I attempted the "add line" after changing the boundary. It didn't add the lines for some reason? I've had problems with this feature before and works fine other times???

[AllenJessup]

As you can see. I managed it in C3D 2017. Sometimes you just have to try adding and deleting in a different order. I started by adding a line between 313 and the closest point, #461, and then worked outward. After creating each line. I deleted a couple of the non-destructive points closest to the midpoint of the line.. When I added the last line. It interpolated to a point below the gap. I just deleted those lines and left the result I showed.

[BrianHailey]

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@srousey74V5X wrote:

If you look at the recent drawing I attached, why can't it simply interpolate between the survey points that are used. The longest leg is 194'. I don't mind it interpolating that long in this example. Just let points 462 & 463 interpolate directly to point 313? Why can it not simply do that?? I went back and did the boundary deselecting the "non-destructive breakline". Then It just stopped the surface at point 461, completely ignoring points 462-464???

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Civil 3D (and every other civil design program that I know of) uses the Delaunay Triangulation algorithm. It triangulates between the points provided in a certain consistent manner. When you add a boundary to the surface, it does it's best to maintain the triangles created from the data but removes the data in the area outside (or inside for a hide boundary) the boundary. If you draw breaklines from points 462 & 463 to point 313, you will likely get the results you want.

This is the purpose of breaklines. C3D doesn't just know what you want. In the areas that it triangulates incorrectly (according to how you want it to be), supplement the point data with breakline data.

[srousey74V5X]

Thank you all for your responses and trying to help me.

[ngerszewski]

Thank you so much. 

Civil3d 2020 kept throwing in all these random points at zero elevation.

This worked for me.