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How can this topology be improved? Multiple attempts and several hours later, I have failed to create a successful all-quad mesh again. I keep trying to visualize face loops that define the edges I need on this object (a screw), but it is very difficult to join these dissimilar sections of geometry together. I have been watching tutorials/speed modelling sessions in an attempt to gain some further insight.

I am guessing that the round part needs to be spherical-ish, because if the verts are not distributed evenly, then it will appear lumpy instead of round/smooth...though clearly, the perimeter loop where the plus shaped area meets the round part has not-evenly-distributed verts all along that edge...

I tried to join the two edges and redistribute the verts to make them spherical, but it looks terrible. Here was that attempt (notice that the ridge is wavy and uneven...), I abandoned this approach after it seemed to be a lost cause:

topology travesty 1, horrible wavy edge

And here is a later attempt, the round part is a bit lumpy/not-smooth...I also realized that there was a triangle here later on too (how would someone fix that? start completely over, since adding geometry would change the number of verts at the joining edge between the two surfaces?):

topology travesty 2, lumpy surface with overlooked triangle

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  • $\begingroup$ you can select in edit mode and scale x to 0 $\endgroup$
    – ruckus
    Commented Jun 9, 2015 at 2:57
  • $\begingroup$ The joining edge is intended to not be flat. It should be in the shape of a plus sign/cross, but shrink wrapped in the z direction to the surface of the spherical/dome shaped part. $\endgroup$
    – Qutorial
    Commented Jun 9, 2015 at 3:09
  • $\begingroup$ Can you post the .blend file? Also, a paintover image indicate the surfaces/profile you DO want would be helpful as well. $\endgroup$
    – Todd McIntosh
    Commented Jun 9, 2015 at 3:28
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    $\begingroup$ Of course you can choose to devote time to minimize triangles and maximize quads. May I ask why that is a concern here? Will the object be highly animated with close up views? The UV sphere and Cone have triangles. $\endgroup$
    – atomicbezierslinger
    Commented Jun 9, 2015 at 6:27
  • $\begingroup$ The restriction to not allow triangles might be unfounded, if the Screw isn't being deformed and has nice smoothing then it's not likely to matter -- but you might have that one edge case when it does (if so elaborate..) $\endgroup$
    – zeffii
    Commented Jun 9, 2015 at 7:08

2 Answers 2

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In Blender most of us would not model a screw by joining two separate meshes, one for the curvature and the other for the groove.

Other 3d packages such as AutoCAD / SolidWorks (and free alternatives) have a different internal representation of shapes. That's why boolean 'carving' is great for those kinds of programs. In those packages geometry remains a mathematical entity until converted to mesh-geometry for export.

In Blender we use mesh geometry (verts, edges, faces) all the way, and that means a different approach is worth considering. You've noticed that trying to match up two very different sections of mesh can be quite a hassle.

Proportional Editing to the rescue!

I'd go for geometry roughly similar to this.

enter image description here

And the use Proportional Edition, move, to push the upper verts into that nice curve. Getting a dome curvature is the smaller problem with this kind of geometry. The biggest issue is thinking ahead about where you want sharp corners and you can do that as a flat surface first and extrude parts down later.

Enable proportional editing and press G to start moving, and Z to exclude the XY movement. Use Shift+Mouse wheel to adjust the sphere of influence. See the manual for more information about proportional editing enter image description here.

The outcome: (with some corrections to the base)

enter image description here

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enter image description here

  • Above and below all quads with a shrink wrap.

enter image description here

enter image description here

  • Please beware of impure and unchaste images below.

  • Consider a boolean modifier A difference B. Sphere minus Cross Sign. You may have already done this. The cross sign has a bevel modifier.

enter image description here

  • Press Apply. You may use a higher resolution sphere (more vertices) for a sharper result.
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    $\begingroup$ OP wants clean topology, in this case I think your answer is a bit off. $\endgroup$
    – p2or
    Commented Jun 9, 2015 at 6:50
  • $\begingroup$ Boolean modifiers generate extra geometry, which is hard to control and especially not clean. To undestand what I mean, see: forums.newtek.com/…. Maybe mention that this is an alternative (fast) way of creating a screw. In addition, I would suggest using the boolean model as base for retopology, which makes sense in many cases to be more flexible in the design process. $\endgroup$
    – p2or
    Commented Jun 9, 2015 at 8:22

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