3D-object along DTM

[Anonymous]

Hello community,

I have a DTM and a landscape protection area as shape file in my project. I am using Autodesk Civil 3D Version 2021. I can import the landscape protection area as a closed polyline. I now want to extrude this to a 3D object, along the DTM. So that the object has the appropriate height.

My first attempt was to project the polyline on the DTM. However, I cannot extrude the resulting 3D polyline. Or is there a solution here?

My second attempt was to extrude the closed polyline into a 3D object. Can I  cut the created 3D object on the DTM / adapt it to the DTM?

The aim is to have a 3D object "lying" on the DTM. So the lower side of the objet is according to the DTM.

I am really very grateful for your help! Many Thanks!

Best regards Annika

[Pointdump]

Annika,
My first thought is that the free Google Earth Pro does this with ease. All day long.

In Civil 3D, as @tcorey said in your >>>Other Post<<<, turn your shapefile lines into Feature Lines and you can have them take on Surface Elevations.

Post your drawing, DTM data, and Shapefiles. Let's see what we can do.
If your data exceeds 71MB, give a link to Autodesk Drive or DropBox or WeTransfer.

Dave

[Anonymous]

Dear @Pointdump , 

thank you for your quick answer! I turned the shapefile lines into Feature Lines and took them on the Surface Elevations. The problem ist I can't extrude the 3D-polyline.. I need it as a 3D-Object on the surface. 

https://we.tl/t-lsPnOXUbcl 

The Dwg- file includes the DTM, the 2D-polyline and the 3D-polyline on the surface. Maybe there is a possibilty to create a 3D-object on the surface? 

Thank you! 

[Pointdump]

Annika,
"...can't extrude the 3D-polyline.. I need it as a 3D-Object on the surface."
Not understanding. When you first mentioned "extrude" I thought you meant buildings. Can you elaborate a little on what you want things to look like?

Dave

[Anonymous]

@Pointdump , 

I want to create a 3D-solid by extruding the closed 2D-Polyline.  I need the polyline as a 3d solid. 

So in this dwg file you see the 3d solid. It has to look like that, but I want the 3d solid on the surface. It should fix on the surface. Now it is under the surface as well. 

https://we.tl/t-xmJhVtG08Z

Thanks for your help!

[neilyj666]

You need to be sure you don't conflate 3D objects from Civil and vanilla CAD (e.g. Civil 3D surfaces and vanilla CAD surfaces are completely different and don't interract with each other)

[Pointdump]

Annika,
I'm not sure what you want to do is possible. Probably the closest you'll get is >>>Like This<<<.

Dave

[Udo_Huebner]

This is a simple task.

1. create a second surface derived from the base surface and use the 2d polyline as outer boundary.

2. increase the elevation of the new surface with the desired thickness.

3. create a volume (3DSOLID) with the command: EXPORTSURFACETOSOLID between both surfaces.

[Pointdump]

Udo,
It sounds genius, but you lost me on Step 3. Can you elaborate a little on that?
Dave

[Anonymous]

Thank you!

Can you explain the steps more in detail, what I have to do in Civil? 

That would be great!

[Udo_Huebner · Accepted solution]

I just created a short Screencast:

https://autode.sk/3qF8iOC

I prefer to simplify the surface1 before creating a volume.

[neilyj666]

I'd concur with the simplify step - civil will hang if there are too many triangles....be sure to save before you attempt the solid extraction

[ChicagoLooper]

The general workflow is this:

1. Create a TINN surface using the DTM as the surface definition. (Do not confuse a TINN surface with a 3D solid.)
2. Use MAPIMPORT command to convert the shapefile entities into a plain vanilla AutoCAD objects. The imported AutoCAD objects, e.g. points, polylines or polygons, will effectively ‘replace’ the shapefile object. MapImport command is part of the Map3D toolset. 
3. Move or ‘raise’ the newly imported points, polylines or polygons to their proper elevation so they sit on the newly created TINN surface. This step involves a Query workflow and an Alter Properties workflow. 

Notes:

Each step noted above is a separate operation. You can’t place shapefile features directly on top of a DTM. Why? Because the shapefile doesn't know how high above sea level it should be raised and Civil3D does not consider the DTM to be a ‘surface.’ 

If you simply raise the shapefile, you will raise it uniformly and all shapefile entities will be at the same elevation. Is that what you want? Or do you really want the shapefile line work to vary from point-to-point and follow the surface undulations? If you want it to vary, then you’ll need to tell each individual shapefile line how high it should be raised and that will involve ‘creating object data’ during step 2 (if they are not raised then the line work will be underneath the TINN surface instead if sitting in top of it). This operation will work, if and only if, your object data has ‘elevation data’ to begin with—although all shapefiles contain data, not all shapefiles contain ‘elevation data.’ Without elevation data, you’ll have to manually click and raise each individual line and that’s tedious, inefficient and subject to user error. 

Civil3D will create a surface using triangulation. Common methods to triangulate is using points, topographic contour lines or rasters such as a DTM. Civil3D also allows you to use a combination of those methods. Creating a 3D solid (instead if a TINN) is not a Civil3D operation, it’s a vanilla AutoCAD operation. The points, contours or raster data used to make the TINN surface is considered the ‘surface definition’ and the definition is what creates the undulations in the surface. The TINN represents natural land, manmade (or graded) land or a combination of both natural and graded land. To achieve realistic TINN surface accuracy, the definition can be fine-tuned by adding more ‘definition’ such as breaklines and boundaries, to name a few. Breaklines and boundaries affect triangulation and triangulation affects the surface undulations. 

To do what you want requires an understanding of shapefiles and the toolset in Map3D and an understanding of TINN surface creation and the toolset in Civil3D. Extrusion and 3D solids are not typically used in Civil3D. 

[Udo_Huebner]

When I simplified the surface1 at the beginning, it took less than a minute to create the volume. Without simplification it took about 15 min.

But if a constant thickness cover is needed, it will be faster to create the volume of surface2 with a thickness/depth of -50. It took less than 12 seconds.

[Anonymous]

What do you mean with simplifing the surface1 at the beginning? In which way? 

[ChicagoLooper]

Take a screen shot of your shapefile. What does it look like when the shapefile is in modelspace?

Take a screen shot of the DTM. What is the DTM source, where did you get it? What does the DTM look like in modelspace?

[Anonymous]

Screenshot 110 shows the shape file. I imported polygon as closed polylines. 

Screenshot 112 shows the dtm. I created it out of xyz-files. 

Scrrenshot 113 shows both. the shape-file as polyline (2D) and the dtm. 

[Udo_Huebner]

I already showed how to get a derived copy of a surface in the previous screencast.

To reduce the size of the volume (3D solid), you can start by using Edit > Simplify Surface to reduce the number of points in your surface.

See this Screencast: https://autode.sk/2YcDYyu

[Pointdump]

Udo,
You, sir, are a genius! I had to watch your video about a dozen times before attempting. I see the need for "Snapshot". Annika didn't include XYZ files. I'd never used that command before. Also hadn't ever done much with Simplify Surface. I used 50% Point Removal. I forgot to save, as @neilyj666 recommended, but still didn't take long to extract solid.
I've heard the term "Solid" bandied about on the Forum, but I'd never used one before and still don't quite know what it is. And I totally don't understand what "constant thickness" means in the context of Vertical Definition, and I'm at a loss trying to understand the 3 choices.

Dave

[Pointdump]

Annika,
OK, I see now you did include all your elevation data for the DTM.
Dave