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I am working on creating an ISO enter keycap in Blender. Everything was going fine, until at the end where I applied a Subsurface modifier. Once I put the modifier on the mesh, it causes extreme pinching in the L-shaped corner of the mesh, where it looks like the mesh is overlapping each other and looks almost like a surf wave. I think it might be caused by the interior corner bevel but I'm not sure, does anyone know why this is happening?

Below are images of the model. Note: I have turned on Cavity in the Viewport Shading menu in order to make the issue more visible.

Top: Top

Bottom: Bottom

The model is also curved as you gave see from the front profile: Curved Top

This is the mesh without a Subsurface modifier: without subsurf

This is the mesh with a Subsurface modifier: with subsurf

A closer look with a Subsurface modifier: with subsurf zoomed in

This is the mesh topology with the Subsurface modifier applied: topology with subsurf applied

A closer look at the topology with the Subsurface modifier enabled: topology with subsurf applied zoomed in

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    $\begingroup$ The problem is that the faces where you have the corner bevels are n-gons (faces with more than 4 verts). Blender favors quad based topology, especially when it comes to shading and subdivisions and even more especially when on "rounded" corners or edges. To fix the problem, you must re-topologize to convert the n-gons to quads, or at least move them to a flat surface (may not be possible with your object). $\endgroup$
    – Christopher Bennett
    Mar 5, 2021 at 1:09

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You have ngons in your mesh.

enter image description here

As I only now see that Christopher explains in his comment above, your pinching is a consequence of using Subdivision Surfaces with non-quad based topology. SubDs only want quads.

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  • $\begingroup$ Hey, Thanks to you and @christopher I was able to convert it into 2 quads and a tri using the knife tool and there is no more pinching now! $\endgroup$
    – Dwo
    Mar 5, 2021 at 3:40
  • $\begingroup$ Glad to hear it. Just realize that the ngon/SubD problem is not limited to polygons with more than four sides. The problem arises with triangles, also. When we say that SudDs want only quads, we really mean they don't want anything but quads. That includes triangles. If you are hard surface modeling, you can often get good results despite having ngons, but only by foregoing the SubD modifier altogether. To make your mesh looks smooth without SubDs takes extra modeling effort. If you aren't hard surface modeling, and need lifelike deformations, ngons must go, or else you'll get trouble. $\endgroup$
    – R-800
    Mar 5, 2021 at 5:59
  • $\begingroup$ Ok, I understand. Thanks for the info! $\endgroup$
    – Dwo
    Mar 5, 2021 at 13:58

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