Rhino Surface help please


#1

I hope one of you can spare a minute and help me with a likely easy problem

I want to create a mobius strip surface but am having trouble getting a good surface. I have the curves drawn and have tried almost everything from lofting, surface from 2 splines etc but not having luck with a clean surface. Hope you can help me out. I have attached the file if one of you can take a look and help me out. thanks

http://fs581.uploading.com/thumb/72/4321fbb0.jpg

mobius strips curve rhino 4.3dm (83.8 KB)


Flow and twist 2
Mobius Geometry Help Please!
(Pascal Golay) #2

Try lofting (Loft command) all your lines- don’t use Closed sweep because it wants to flip the lines at the end. Make a BlendSrf to span the last bit and then if needed, MergeSrf to make it all one surface. ''Any luck?

-Pascal


#3

Granted, I’m not actually contributing much to the OP’s query. I’m just posting this geometry as an example of a periodic (0 to 4Pi) Mobius strip.

I’m not sure what would be a good way of recreating this in Rhino - other than manually realigning CVs of a round curve extrusion. This was created programmatically in AutoCAD.

Just thought that some may find it interesting.
MobStrip.3dm (41.3 KB)


#4

I tried lofting but there is a slight curvature to it… The sections don’t come out straight like the red profile lines. Maybe that is the limit for a mobius strip xD


#5

i think pascal was saying to select all the red lines (and the green one) then loft those…
there will be one section which doesn’t fill in… use blendSrf then mergeSrf to fill the gap.


#6

there’s always this little trick…

that said, i’m not sure if this is a ‘real’ mobius – or, i have no clue what 0 to 4Pi is supposed to mean… you could of written 跆拳道 instead and it would of meant the same to me :wink:


#7

ah thanks for clearing that up… Pascal’s method work totally fine :slight_smile:

Nice mobius trick btw, although it wouldn’t help me i think as I need the curves to be similar to ones I have


#9

The idea behind my geometry was to create a surface the behaved more like a true Moebius. By that I mean that the surface can be evaluated through the U direction to a position on both sides. See the script.

I chose 4Pi to resemble a circle. With a circle, advancing 2Pi will return you to the start point. With a Mobius, you are at the start point, but on the underside of the surface. 4Pi returns you to the true start point.

Option Explicit

Sub SurfNormAtParam
	Dim srf
	Dim domU, domV
	Dim domInput(1)
	Dim tanVec
	Dim arrdata



	With Rhino
		srf = .GetObject("Pick a surface", 8)
    
		If (VarType(srf) <> vbString) Then Exit Sub
    
		
		domU = .SurfaceDomain(srf, 0)
		domInput(0) = .GetReal("U Param, input Real Number between " & CStr(DomU(0)) & " and " & CStr(DomU(1)), DomU(0), DomU(0), DomU(1))
		
		
		domV = .SurfaceDomain(srf, 1)
		domInput(1) = .GetReal("V Param, input Real Number between " & CStr(DomV(0)) & " and " & CStr(DomV(1)), DomV(0), DomV(0), DomV(1))
		
		arrdata = .SurfaceCurvature(srf, domInput)
		     
		tanVec = .AddLine(arrdata(0), .PointAdd(arrdata(0), arrdata(1)))
		
      
	End With
End Sub
SurfNormAtParam

Rhino.SurfaceCurvature oddity