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I'm trying to recreate some geometry for a lighthouse model. A particular feature of this goal mesh is that it has spiral loops going around the cylindrical lighthouse. (ignoring the boolean cutout holes in this example)

Goal shape for mesh

I've tried a few different things, notably trying to use a screw modifer which causes the faces of the cylinder to loose flatness/smoothness. And I've tried using "poke, and convert to quads" to generate this shape. Both of these attempts cause the mesh to be less smooth, and looses the vertical loops. screw example

poked faces turned into quads example

How on earth might this shape be made? Hugely struggling to wrap my head around this mesh. Thank you for any suggestions!

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  • $\begingroup$ That's funny, I was just thinking about shapes like this.. It tapers as it goes up? And how many blue stripes are there? $\endgroup$
    – Ron Jensen
    Aug 31, 2021 at 19:08
  • $\begingroup$ 5 stripes for each of the 2 colors. $\endgroup$ Aug 31, 2021 at 20:10
  • $\begingroup$ and yes it has a very gradual taper, but I figured I could just cheat on that and proportional edit scale down the very top loop after the fact. $\endgroup$ Aug 31, 2021 at 20:11
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    $\begingroup$ Doing the spirals with a material might be easier. Here is a tutorial for doing it procedurally. $\endgroup$ Aug 31, 2021 at 23:56
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    $\begingroup$ @MartyFouts Hmm. A procedural spiral can be much easier than in that toot. See my edit. $\endgroup$
    – Robin Betts
    Sep 1, 2021 at 6:20

2 Answers 2

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Here is my technique, such as it is:

  • Enable Add Curves: Extra Objects add-on in preference if you haven't already.
  • Create an Archemedian Spiral and give it 3 turns and a height of 1. Set Steps to a value that will give you a reasonable smoothness. I selected 32.

Last Operation Panel showing curve settings

  • In Object mode, select the spiral, navigate to the Object->Convert submenu and select Mesh
  • In Edit mode, select all and extrude along the Z axis until the extrusion just touches the existing curve:

Extrude until the points touch

  • Select all and Merge by Distance
  • Loop Cut and Slide to add 9 loop cuts. This will give you the 10 bands you want.
  • It's easiest to add materials at this point. Add a new material. That will make the object that material. Add a second new material. Select every other band and apply the material to those bands.
  • In Object mode, Shade Smooth

All that's left is to trim the top and bottom. Probably the easiest way to do this is with a knife project.

  • In Object mode, add a plane.
  • Rotate it 90 degrees on the X axis.
  • scale it up on the X axis.
  • Apply the scale and rotation.
  • Move it -2 on the Y axis.
  • Select the plane and then the spiral thing.
  • In front view, enter Edit mode and select Mesh->Knife Project
  • Make sure Cut Through is set
  • Go to Vertex Select mode, invert the selection, and delete vertices.

For a final touch, in object mode, set origin to geometry and set the location to the origin.

final spiral image

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You must be assigning the Screw modifier to an unsuitable original mesh? Half the point of using Screw, as opposed to twisting a cylinder, is that you can preserve the verticals, and wind up with near-planar quads.

Start with a simple vertical edge, away from its object origin on one axis..

enter image description here

You can even use further modifiers (Displace, or maybe Simple Deform > Taper) aimed at a Vertex Weight Proximity weighted vertex-group, to do the tapering for you...

enter image description here

..but you probably want to level the top and bottom of the spiral by hand, which means applying the Screw, anyway, so that would be too involved. Happy to help, though, if you want to go that way.

EDIT:

@Marty Fouts made a comment, while I was editing this answer: I agree with him, it would be much easier to do this with a little procedural shader, taking advantage of the default UV of a cylinder, unless you need the spiral in the geometry for brickwork, or somesuch:

enter image description here

Adjust the scale of the Wave texture to vary the number of turns. Adjust the Z-rotation in the Mapping node, tilting the stripes across the UV square, marrying them at the jump from U=1 to U=0, and you have a spiral.

That would save you quite a few chores, in modelling.

enter image description here

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  • $\begingroup$ I think this would produce a single spiral, no? But I believe the OP wants 10 adjacent spirals so they can have alternating stripes, five in one color, five in another. $\endgroup$ Sep 1, 2021 at 1:05
  • $\begingroup$ Hi, @Marty! What is fixed, is the number of turns. If you want 2 or more alternating stripes, just subdivide the edge? $\endgroup$
    – Robin Betts
    Sep 1, 2021 at 5:36
  • $\begingroup$ Indeed! I should have figured that out on my own, given that I do exactly that in my answer. Ooops. $\endgroup$ Sep 1, 2021 at 13:49

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