Subdivision smoothing at the poles. If you are trying to create a sphere-like top from a low-poly cylinder, the algorithm reaches a singularity (a pole) where dozens of edges meet. SketchUp hates poles. It will crack every time.
SketchUp will force a new triangular face to form, closing the crack.
Is the object a , or raw, loose geometry? sketchup round corner crack top
Is the top face a or a complex, curved shape ? Share public link
, which is a more advanced version of the tool designed to handle complex corners and non-planar faces more robustly. SketchUp Community Subdivision smoothing at the poles
The original RoundCorner is older; Fredo6 released FredoCorner specifically to handle more complex geometry with a better algorithm that reduces face-cracking. Alternative Manual Method
This article is your complete guide to diagnosing, fixing, and permanently preventing the "crack top" issue when using the Round Corner plugin. We'll move beyond simple troubleshooting and explore the core principles of SketchUp's geometry engine, giving you the knowledge to master rounding corners, whether you're using Round Corner, the more advanced FredoCorner, or a mix of native tools. It will crack every time
In the RoundCorner dialog box, ensure you are only selecting the outer edges and not the corner vertices themselves if they are causing issues. Use the selection modes to select only "plain edges". Pro-Tips to Prevent Top-Surface Cracking
Exit the group and scale it back down by 0.01 (or 0.001 ) to return it to its original, real-world size. The tiny faces will remain intact because SketchUp can maintain small geometry better than it can create it. Method 2: Flatten and Clean the Top Face
