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I hope it's OK to ask this question here. I'm asking for my son who has been playing with Blender for a school project. I'm sure I won't be using the correct terminology to describe what he is doing or what the problem is.

He's made a Christmas light bulbed-shaped object which looks pretty good, but he's noticed some imperfections with the shape when rotating.

When we bring up the object in Blender and rotate it appears to wobble which I guess means imperfections.

What we're looking for is help in how to fine-tune this shape. The Blender file should be attached.

We were first trying to modify a sphere by dragging vertices individually but we quickly realized this probably isn't the easiest way to do things. He then discovered that by highlighting a horizontal line of vertices and relocating up and down by use of a pin type image that can be clicked to move the line was a better approach or got him closer to what he wanted.

Would appreciate instructions on how to perfect this shape/object!

Any early guidance is appreciated!!

Superfreak3
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    You can upload your file here - https://blend-exchange.com/ - copy the link they give you then edit this question and paste the link in. – Christopher Bennett Feb 27 '23 at 02:10
  • There are also a myriad of things he can do to fix this - the first that comes to mind is to select and delete all the faces on the "bad" half, and then use a Mirror Modifier to complete the object. – Christopher Bennett Feb 27 '23 at 02:12
  • Also, if he is just learning blender, I would highly recommend this series - https://www.youtube.com/watch?v=nIoXOplUvAw&list=PLjEaoINr3zgFX8ZsChQVQsuDSjEqdWMAD - it's probably the best starting point for many users to learn the "functional in's-and-out's" of blender, and almost all users here will know what you're talking about if you have questions throughout. It's a bit like an achievement award - "Have you done the donut?" – Christopher Bennett Feb 27 '23 at 02:16
  • Hello, you can also show a screenshot? – moonboots Feb 27 '23 at 08:33
  • Thanks for all of the tips. I've uploaded the file and will definitely check out that instructional youtube series! – Superfreak3 Feb 28 '23 at 00:51
  • Hi @Superfreak3, and welcome! .. apart from a slight pinching at the poles of your UV Sphere, and maybe a tiny discontinuity in curvature, the model looks OK. Do you mean it doesn't match your reference image? If so, we can't tell, because the image isn't packed in the .blend file. You can make a screen-grab, and add images to your question. (Maybe the reference itself, so we can use it, and maybe an illustration of the mismatch, or your meaning of imperfection) – Robin Betts Feb 28 '23 at 07:32
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    Thanks @RobinBetts. The shape really doesn't match our reference image, but the difference is so small and inconsequential. We were just trying to see how we can clean up the model/refine it to clean up such things like tht pinching and discontinuity in curvature. The goal is to get things printed in the end so wondering if any of those things would show up in the print. – Superfreak3 Feb 28 '23 at 17:38
  • Thanks @RobinBetts, I'll be watching for suggestion(s). – Superfreak3 Mar 01 '23 at 00:04

1 Answers1

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It's hard to answer this one in a very definite way. I'm not picking up the 'wobble' you're referring to, unless it's the very slight consequence of the pinch-poles of the UV sphere. The pinching is chiefly a shading anomaly, to do with the way normals are interpolated by the renderer, not a geometric anomaly, so shouldn't make any difference to a print. To be honest, the model looks fine.

In general, if you needed to fine-tune the curvature of a surface like this,some of these moves/features might be typical:

  • Generally working under large-diameter Proportional Editing
  • In any tool or any numeric field, Shift-dragging to gear down mouse-movement
  • Working under Smooth and Subdivision Surface modifiers until happy, and then applying, at least Smooth
  • SShiftZ .. (shift-drag) to scale latitudes in XY only
  • G G to slide latitudes up and down longitudes, while trying to keep intervals changing smoothly.

However, if you're fanatical about continuity in curvature, in the same way as a CAD-designer of highly reflective objects might be, any manual adjustments of elements are almost bound to mess it up.. I think you have to automate it, somehow. An obvious route is to rely on the inherent continuity of a spline with aligned control-points. Blender curve-editing is not the friendliest, but it's improving....

  • Create a Curve > Bezier Curve. I've declared mine to be 2D in its Data tab > Shape panel, to guarantee it stays flat in its own object-XY. not strictly necessary. (You can just ensure it's always scaled to 0 in the appropriate direction in Edit Mode, instead)
  • In Edit Mode, ensure the end-points are at exactly 0 in global X and Y. You can enter that numerically in the 3D View N panel , Item > Transform fields
  • Subdivide the curve once, and set all control-points to 'Aligned'...

enter image description here

(Left, Object Mode, displaying object axes, in my case. Mid, Edit Mode.)

  • Scaling the end-points to 0 in Z about a Median Transform-Pivot will ensure the tangents at top and bottom will be horizontal.

Now you have only three control-points with handles to adjust, in an orthographic front-view (Numpad 1), to get any smooth profile you want.

The profile can be given Screw and Weld modifiers, to create the surface of revolution. Smooth and Subdivision modifiers might be appropriate. When happy, a copy of the object can be converted to a mesh.

The difference between your mesh-edited surface, and this curve-edited surface is tiny, but shows up under a stripe-matcap:

enter image description here

Front and top-views, curve-model in green, with better continuity in curvature.

For your print, IMO, all this post is way over the top. But maybe it suggests an alternative route.

Robin Betts
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