Seeing "cracks" or gaps on the top face of your SketchUp model after using a rounding tool is a common headache. It usually happens when the geometry gets too complex for the plugin to calculate cleanly, or when SketchUp's internal "tiny face" limit is triggered. Common Causes of "Cracks"
The "Tiny Face" Problem: SketchUp has a hard time creating faces smaller than ~1/16th of an inch (1.6mm). When you round a corner with many segments, the resulting triangles at the very top can be so small that SketchUp fails to fill them, leaving a "crack" or hole. sketchup round corner crack top
Tight Corner Overlap: If your rounding radius (offset) is larger than the distance to the next edge, the plugin "overflows" and creates overlapping or broken geometry. Seeing "cracks" or gaps on the top face
Non-Planar Surfaces: If the top face isn't perfectly flat, the plugin may struggle to "stitch" the new rounded geometry to the existing face, resulting in visible seams or missing surfaces. How to Fix and Prevent Cracks Part 4: Prevention – How to Avoid the
SketchUp cracks or missing faces during rounding occur when geometry falls below the application’s 0.025 mm tolerance limit, commonly resolved by scaling up the model by 100x or 1000x before applying the RoundCorner tool. Alternative solutions include reducing the segment count or switching to the more robust FredoCorner plugin for complex intersections. To learn more about fixing these issues, see the discussion at SketchUcation. Round Corner Issues | sketchucation
The best cure is prevention. Here is your pre-flight checklist before using Round Corner on a top face.
This is the culprit 90% of the time.