Better Crack Top | Sketchup Round Corner

Mastering SketchUp: How to Fix "Crack Top" and Geometry Issues in Round Corners

If you’ve spent any time 3D modeling, you’ve likely encountered the frustrating "crack top" or broken geometry issue when trying to round off a corner in SketchUp. This typically happens when the software's internal engine struggles to calculate complex intersections, often resulting in missing faces or "cracks" on the top surface.

While SketchUp is incredibly versatile, it wasn't natively designed for complex edge rounding. To get professional results, you’ll almost always need a specialized extension or a few expert workarounds. 1. Why Do "Cracks" Appear?

The "crack top" issue usually stems from one of three problems:

The Tiny Face Problem: SketchUp has difficulty forming very small faces (under 1mm or 1/16 inch). When you round a corner with a high segment count, the resulting faces may be too small for SketchUp to "heal," leaving a gap or crack.

Non-Planar Top Surfaces: If the top face of your object isn't perfectly flat, standard rounding tools will fail to calculate how the curve should meet the surface, leading to geometric "tears".

Too Large an Offset: If your rounding radius (offset) is larger than the available surface area, the geometry will overlap and break the top face. 2. Best Solutions: FredoCorner vs. RoundCorner

The most common way to solve this is by using extensions from developer Fredo6. There are two primary options, and knowing which one to use is key to avoiding top-face cracks.

FredoCorner (Recommended): This is the newer, more powerful tool. It uses an improved algorithm that handles complex, irregular shapes much better than its predecessor. It includes a Repair button and parametric abilities, allowing you to edit or undo rounding if it creates a crack. sketchup round corner crack top

RoundCorner (Legacy): While simpler and faster for basic cubes, it is "greedier" with face generation and often fails on non-orthogonal edges. If one fails, many pros keep both installed as a backup. 3. Step-by-Step Fix for Cracked Geometry

If your top face is cracking, follow these steps to achieve a clean finish:

Scale Up (The "Dave Method"): Before applying any rounding, scale your entire model up by 10x or 100x. This bypasses the "tiny face" limitation. Once the rounding is finished, scale it back down—the tiny faces will remain intact.

Reduce Segment Count: A common mistake is using too many segments (e.g., 12 or 24) for a small corner. Lowering this to 6 segments is often enough for a smooth look while keeping the geometry manageable and less prone to breaking.

Check for Overlaps: Use the Preview mode in FredoCorner to see if your offset is too large. If the preview shows red or overlapping lines, reduce the radius until they disappear.

Manual Re-topping: If a crack persists, delete the broken top face, round the edges, and then use a tool like Curviloft or the native "Create Face" tools to manually stitch the top back together. 4. Native Alternatives (No Plugins)

If you prefer not to use extensions, you can use the Follow Me tool: Curved face problem - SketchUp Forums

Introduction

SketchUp is a popular 3D modeling software used by architects, interior designers, and product designers. One of the common issues faced by SketchUp users is the "Round Corner Crack Top" error. This report aims to provide an overview of the issue, its causes, and possible solutions.

What is Round Corner Crack Top?

The "Round Corner Crack Top" error occurs when using the "Round Corner" or "Fillet" tool in SketchUp to create rounded corners on a 3D model. The error causes the top surface of the model to become distorted or "cracked" when trying to apply a rounded corner.

Causes of Round Corner Crack Top

After analyzing various user reports and forums, the following causes have been identified:

1. Complex Geometry: The "Round Corner Crack Top" error often occurs when trying to apply a rounded corner to a model with complex geometry, such as multiple intersecting surfaces or non-planar faces.
2. Insufficient Faces: When a model has insufficient faces or is not properly divided, the "Round Corner" tool may struggle to create a smooth rounded corner, leading to a "cracked" top surface.
3. Incorrect Tool Settings: Incorrect settings or tolerances in the "Round Corner" tool can also cause the error.

Solutions

The following solutions can help resolve the "Round Corner Crack Top" error:

1. Simplify Geometry: Try simplifying the model's geometry by dividing complex faces or removing unnecessary details.
2. Increase Faces: Increase the number of faces on the model by using the "Intersect Faces" or "Divide" tools to create more subdivisions.
3. Adjust Tool Settings: Adjust the "Round Corner" tool settings, such as increasing the "Radius" or "Segments" values, to achieve a smoother rounded corner.
4. Use Alternative Tools: Consider using alternative tools, such as the "Soften" or "Smooth" tools, to achieve a similar effect.

Workarounds

If the above solutions do not resolve the issue, the following workarounds can be tried:

1. Manual Modeling: Manually model the rounded corner using the "Draw" and "Edit" tools.
2. Plugins: Utilize third-party plugins, such as "Round Corner" or "Fillet Plus", which may offer more advanced features and better handling of complex geometry.

Conclusion

The "Round Corner Crack Top" error in SketchUp can be caused by complex geometry, insufficient faces, or incorrect tool settings. By simplifying geometry, increasing faces, adjusting tool settings, or using alternative tools, users can often resolve the issue. If necessary, workarounds such as manual modeling or using third-party plugins can also be employed.

Recommendations

• When working with complex models, try to simplify geometry and increase faces to prevent the "Round Corner Crack Top" error.
• Regularly update SketchUp and plugins to ensure access to the latest features and bug fixes.
• Consider using alternative tools or workarounds if the "Round Corner" tool is not producing the desired results.

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Step 3: Reverse the Faces

Sometimes the face exists, but it is reversed (blue instead of white). Right-click the area > Reverse Faces.

Solution C: Using Artisan or SubD (For Organic Tops)

If you need a perfectly smooth, crack-free top (like a car fender), stop using Round Corner for the top vertex. Use Artisan or SubD (Subdivision) .

1. Draw a low-poly box.
2. Subdivide it 2 times.
3. Shift+Click the top vertex to "smooth" it.
4. Subdivide again. The crack will vanish because SubD creates continuous curvature, whereas Round Corner creates discrete geometric offsets.

Preventive workflow recommendations

• When rounding corners, create the fillet on a grouped component to limit propagation of stray geometry to the main model.
• After using fillet plugins, always inspect and run a cleanup pass.
• Keep a backup copy before destructive boolean operations so you can revert if seams appear.

2. Soften/Soften Coplanar Lines

After running Round Corner, Zoom in on the crack.

• Triple-click the object to select all geometry.
• Go to Window > Soften Edges.
• Drag the slider to 45–90 degrees.
• Result: Often, the "crack" is just an unsmoothed normal line. Softening it makes it vanish visually without changing the mesh.