Creating Complex Surface from edges and curves

Hi all,

I’m after some help to create what I think is a fairly complex surface; I’ve got the start and finish edges, and a curvature it needs to follow, but using the likes of Loft and EdgeSurface doesn’t seem to be working for this.

Attached are some images. Any tips or advances commands/tools that would help?

The first is the perspective view, second is side view showing the x-axis curve the surface needs to follow and the third is the actual thing I’m trying to achieve.

Screenshot 2023-07-29 155730

Thanks in advance,

Help is more likely if you post a .3dm file with the applicable geometry.

Thanks David, See below file.

The surface needs to align with the perimeter curves so it can form a closed surface on the model. I’ve tried Loft, Edge Surface and a few others with no luck. The closest I’ve come resembles the shape of the roof, but the edges don’t align and joint.

Lines.3dm (42.9 KB)

Any help would be appreciated, and if possible, step by step advice.


That shape looks deceptively simple but is actually complex. Accurately modeling it will require several surfaces with appropriate matching between the surfaces. It will be a week or so before I will have time to work on it.

Hey Mitch,

What object is this? I’m having a go right now and I’d like to Google it to see it from diff angles/get a better understanding of it.

Hi Mitch -it looks to me like the general construction can be something like this:


where my colored curves are tangent arcs and the two inner surfaces EdgeSrf, the intersecting corner ones are ExtgrudeCrv (the straight one) ExtrudeCrvAlongCrv for the curved one. The corner transition must be something like what I have there but that is not quite rigjht.


I think there is no one click solution for this. You will need several surface patches for the roof (…of a train carriage?).

I would model this from the beginning like this:

  1. Extrude the basic shape
  2. Fillet the edges (red with little bigger radius than green)
  3. Shape the top surface by control point editing
  4. Rematch the fillets back to the top surface

Hi Vince,

Here’s some more photos of it. Correct; it’s the end of a train carriage which is rather unique.



Thanks for the pictures; which train model is it?

Hi Vince,

It’s a 65’ long carriage that was built in Australia; the terminal cars had this unique roof layout.

I’ve not had a chance to try out the above advice, but if anyone else has had a go/success that’d be brilliant.

Hi. I think using Networkrsf can help you. It’s good for complex surfaces and you have guide curve too.