Create a cylinder surface

[TONY7873]

I am developing a surface for a hydraulic model and need to include vertical objects. I have a topo surface and need to add bollards and tree trunks (ie cylinders) to the topo surface. Ive already added walls and a building using feature lines. 

Any suggestions on how to do this using C3D 2015? Thanks!
Tony

[Joe-Bouza]

You want that to be part of your TIN? >> circular FL at base FL offset to cylinder height with a slight offset

Don't know why you would want that other than rendering. >> 3d modeling Work space >> circle push pull, then set elevation

[TONY7873]

Thanks Joe, I was just working through this. Yes as part of the TIN. We are developing a 2-d hydraulic model for sediment transport and the cone screen, trees, bollards etc are flow obstructions....

Just had success with this approach: Create polygon with 250 sides to approximate circle, set elevation. Slight offset, new elevation. Add as breaklines. I would rather use a FL but I have not seen a way to make a circular FL, Ive used 2 arcs but they do not give enough vertices.

I was under the impression that you cannot merge solid objects from the 3-d modelling workspace with TINs... maybe I need to reveisit this.

Thanks for the input, Im still working on this.... 

Tony

[Joe-Bouza]

I think you are correct Tony; I don't think you can merge acad solids. that suggestion was for rendering only.

Glad you had success. Sounds like an impressive drainage model.

[Joe-Bouza]

Cool! I think I'll use that scene on my model railroad 😉

[BrianHailey]

No need to create polygons, just use the donut command, convert them to featurelines, stepped offset to the inside and up to the top.

The donut command creates a polyline with two half circles. When you convert them to featurelines, they lose their width.

[ksorsby · Accepted solution]

Not sure if it's the same as what you want but I used this for developing complex ground models for overland flow modelling, where there are circular structures as obstructions.

1. Create a donut at the rightlocation/diameter as your desired base outline, width doesn't matter
2. Convert to feature line
3. Offset feature line inside by 10mm (say) and vertically to whatever height you need
4. Drape original feature line in 1) on the underlying ground model TIN to generate Level Points but still using circle geometry. IP's will ruin the geometry
5. Create new surface called 'Structure1' or whatever
6. Add inside/top and outside/bottom featurelines to create a TIN 'cylinder'
7. In a new surface called 'Modified Topo', paste your Survey/Existing Ground surface
8. Add in the feature line outside/bottom in 4) as a breakline
9. Paste 'Structure1' into 'Modified Topo'
10. Add outside/bottom as in 4) as boundary as necessary

Worked every time here.

Hope this is ok,

Kevin

[Pointdump]

Tony,

When I saw this:

The first thing that came to me was the Geotechnical Module:

Dave

[troma]

Also, if you already had circles, mapclean can convert them to polylines.

[TONY7873]

Yep that works, Thanks. The donut commmand is a new one and useful. Once I realized that Level Points are "Elevation Points" I added those and it made a nice smooth cylinder. Thanks for the input!

[TONY7873]

Mapclean is a new command for me, also useful. Thanks!

[ksorsby]

Yes, I know them as Level Points as that's what they used to be in the UK packs. For some reason they are now Elevation Points in the 2016 UK pack.

They are really powerful for forcing triangulations on feature lines, particularly curves.

Kevin

[TONY7873]

Thanks or the help everyone. Image attached of roughed surface. Here was my workflow for this task (units are feet):

1) Build the surface as per usual. The point at the base of the tree is at the ground and is used to build the surface.

2) Locate trees. Use donut command defined by the tree diamter

3) Create Feature line from donut

4) Add Elevation Points along circular FL at increment of 0.3 

5) Assign elevations to FL from the surface

6) Offset FL by 0.1 and add 10 feet to the elevation to make the "top circle".

7) For the top circle adjust elevations so they are all the same (to make it clean)

😎 Add both Feature Lines to the surface.

Steps 4 and 5  are important and help it blend into the surface, especially when the trees are on a slope. This minimizes surface clean up after its added as a breakline.

Now I need to look into better 3-D visualization of the surface!

[troma]

Normally I would say you didn't nee to add extra Elevation Points, just use the Insert intermediate grade break points option when you do the elevations from surface. (This option automatically adds an elevation point anywhere where the featureline crosses a surface TIN line.) However, if your circle didn't cross any TIN lines, it would end up with just two elevations, and it really needs at least 3 elevation points to define the plane that it sits on.


If I were you, I'd attack it this way:

4) Add Elevation Points at two midpoints of the featureline. (You now have four points: two PIs and two Elevation Points)

5) Assign elevations to FL from the surface, using the Insert intermediate grade break points option

6) Use 'Stepped Offset' command to offset FL by 0.1 horizontally and 10 feet vertically to make the "top circle".

7) For the top circle delete all elevation points (to make it clean)

😎 Add both Feature Lines to the surface, assigning a low Mid-ordinate distance.

A mid-ordinate distance that is small enough will make the surface triangulate nicely around the circle. You'd have to play with it a little to find the right distance. Maybe 0.05'?

[troma]

Hmm, little rethink. You need at least three points to define each plane. So for every triangle that the circle crosses onto, it will have a point at both TIN lines, but it will need one more in the middle to properly sit the featureline on the surface.