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I'm trying to learn subdiv modelling, but now I'm facing with some issues. That is clear, when I want to sharpen an edge or a corner I have to use support loops. My issue is: when I do that, support loops also running over areas where I would like to have smooth surface. Tried to even out edges, but the distortions are still visible on the smooth surface.

Is there a way to fix this without using edge creasing or bevel? (producing unnatural results or too sharp edges,but maybe I'm doing it wrong)

Thank you!

enter image description here

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EDIT: Tried to crease, it does not work :< enter image description here enter image description here

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  • $\begingroup$ Creasing should work. If the edge is too sharp, maybe try a lower amount? Sometimes a 0.01 difference in the setting just make everything too sharp. $\endgroup$
    – Paul
    Dec 31, 2019 at 12:22

2 Answers 2

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You have to be careful about adding edge loops on curved surfaces. As you've already discovered, Subdivision Surface modifiers average out the vertices, so those additional edge loops pull the local faces towards itself. Thus, you should try to only add in support edges around the edges that need support.

Desired Result

Here's the topology I used to get that result:

Geometry

When you're adding support edges/loops, here's are a few things to keep in mind:

  • Try to isolate the supporting edges. Have the topology of the model surround the protruding mesh and its supporting edges. In this case, notice how none of the supporting edges go beyond the original mesh from the subdivided cube. Using the Knife tool instead of Edge Loops can help here.

  • Avoid triangles, n-gons, and impossible faces (Ex: imagine a flat square, then you pull one of the corners upwards along the face's normal. IRL, this would end up as two triangles with an edge across the square's diagonal, but that edge is not added in 3D modelling). These often cause shading issues.

  • Avoid excessively or unnecessarily close vertices. This isn't always a problem. but if possible, merge them together, making sure you aren't messing up your support loops. This can be done by selecting a vertex and double pressing G to slide the vertex along its connected edges into an adjacent vertex. If you have auto-merge vertices enabled (shown below), the two will be merged together. Alternatively, you can enter Edit Mode and select Mesh > Clean Up > Merge by Distance in the top left corner of the 3D Editor.

Automerge vertices

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    $\begingroup$ Thank you for the detailed answer! Yes, the problem begins there, when I'm trying to avoid ngons and triangles. Your attached example also conatains some n-gons, if I try to eleminate those, the situation is the same as in my first post. I was not aware of automerge, good to know, thanks! (used alt+m) Did some additional reading in the topic, and there is no perfect solution (except nurbs modelling but thats another world), but there are tricks for edge loop reduction, moving poles, etc. A really nice article about the possible solutions of subd modelling: topologyguides.com $\endgroup$
    – Grey
    Jan 1, 2020 at 20:50
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There is no perfect solution, but found two really good articles in the topic of subd modelling.

https://topologyguides.com/

https://www.artstation.com/andrewhodgson/blog/4aZN/modeling-blog-03-approaching-the-asset

Let me quote the author, Andrew Hodgson:

"Modeling on Curved Surfaces

This is something that comes up quite a lot and people are always searching for a magical topology flow to prevent pinching on curved surfaces. The reality is there isn't one and you will always get a pinch. What it comes down to though is how much you can hide the pinch depending on how close you can see it. If your curved surface is very hero, you simply just need more topology on the curved surface to make the pinch smaller. That is it. If the shape is much further away the pinch wont matter so much. You might not even have to model out of the curved surface and can simply penetrate 2 shapes. I would do this if you can."

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