Hello!
We are a company that makes canopys and upholstery based in Norway and we just started using Rhino 7 instead of an outdated program. So we could use some tips and tricks with the workflow, and if we are doing something wrong. To get the pins and dots-placement from the boat we use a program called Photomodeler.
We would appriciate if someone could take a look at this file and tell us if we are doing something wrong? Any tips is appriciated. testfile.3dm (1.0 MB)
Hello Lasse,
Photomodeler is nice and I guess you take additional manual measurements for the critical stuff.
I’d use smooth curves instead of polylines to create the surfaces. In your sample you can simply _ChangeDegree from 1 to 3 with the deformable option. Alternative ways would be _CurveThroughPolyline, _Rebuild or _FitCrv…
I don’t know how you created the surfaces but I use the _DevLoft command for these things to get surfaces with Gaussian curvature close to zero, which means that it should be developable without too much deviation. Use the _CurvatureAnalysis command to check your surfaces and always compare the area of the unrolled shape.
Developable surfaces in Rhino have to be strictly straight along one of the surface’s directions. But of course such a canvas in real world will always have some negative curvature. I guess you have the experience to correct the unrolled cutting shape accordingly and avoid wriggles and get nice tension everywhere.
You can also simulate the membrane with Grasshopper/Kangaroo and _Squish the shape, but this is a bit more complicated…
Hope this helps and does not confuse too much.
Jess
Hello Jess!
Thank you so much for your reply.
I used Surface from network of Curves, didn’t work all the time tho, so I may have used Loft also.
So by using “_ChangeDegree from 1 to 3” on my imported lines I smooth them out?
May I ask how “_CurvatureAnalysis” works?
I also sent you an email regarding exporting unrolled surfaces. Because I cant seem to get the points with the xport- The points tell me where the drilled holes are supposed to be…
I am also wondering what is the best way to draw windows on the surfaces? So I can show the 3D-model to my customers? 
Again, thank you.
Developable surfaces always are strictly straight in one direction, not just in Rhino. Fabric under tension will usually not be exactly a developable surface but will have negative Gaussian curvature. Unless there is an air pressure difference between the sides of the fabric (such as in a balloon) the Gaussian curvature will never be positive.
First step is draw a curve on the surface of the outline of the window. There are several methods to do this:
a) Draw the curve directly on the surface using InterpCrvOnSrf
b) Draw the curve directly on the surface using CurveOnSurface For this command you need to download and install a free plug-in: https://www.food4rhino.com/en/app/curveonsurface-0
c) Draw the curve on the Cplane in a view. Then Project the curve onto the surface.
After the outline of the window is drawn on the surface, Split the surface using the outline curve.
Change the material properties of the window so it is transparent or semi-transparent.
Hello Lasse,
NetworkSrf is possible but not helpful with developable surfaces. Use the -DevLoft command with a hyphen to get more options. Note: The Loft command with the developable option is something different!
Well this was just a quick hack to get a smooth curve to start with. I guess what you really want are rationalized curves which can be fabricated easily (usually arc and lines in a plane). See attached file…
This is a pretty complex topic. I’d recommend to start with the Rhino help. If you have further questions feel free to ask: https://docs.mcneel.com/rhino/7/help/en-us/index.htm#commands/curvatureanalysis.htm#(null)
MarineCanvas_jM.3dm (787.9 KB)