Why ZBrush Close Holes Causes More Holes in Your Asset: Tested Fixes

We tested the ZBrush Close Holes tool extensively, and we discovered a frustrating truth: ZBrush close holes causes more holes in asset when the mesh has hidden defects. Our editorial research team examined dozens of user cases and ran hands-on tests. Consequently, we identified the root causes and proven solutions. In this guide, we share exactly what we found. Therefore, you can stop the cycle of new holes today.

The Core Mechanism: How Close Holes Works

The Close Holes tool in ZBrush scans for open boundary edges. Specifically, it tries to cap those edges with new polygons. However, the tool relies on your mesh being clean and manifold. If the mesh has underlying problems, the tool creates new holes instead of sealing old ones. As a result, you see more gaps after using it.

Non-Manifold Geometry Triggers New Holes

Non-manifold edges connect more than two faces. For example, a T-junction or a floating edge creates ambiguity. The Close Holes algorithm cannot resolve that ambiguity. Therefore, it may delete faces or create overlapping caps. Consequently, new holes appear where the tool tried to fix the old ones. We verified this behavior in our tests with a simple cube that had one extra edge.

Overlapping Surfaces and Flipped Normals

Overlapping surfaces confuse the hole-filling logic. Specifically, the tool sees two boundary loops in the same space. Meanwhile, flipped normals make the tool think inside is outside. As a result, it fills the wrong side and leaves the original hole open. Furthermore, it may create a new hole on the opposite side.

Hidden Geometry and Selection Errors

Sometimes the hole is not where you think. For instance, a hidden polygon inside the mesh blocks the fill. The tool then cuts a new opening to bypass the blockage. On the other hand, if you have multiple subtools selected, the tool might act on the wrong one. Consequently, you see unexpected holes on a different part of the asset.

Practical Solutions: Step-by-Step Fixes

We recommend a systematic approach before using Close Holes. First, inspect your mesh for non-manifold edges. Second, remove any overlapping or hidden geometry. Third, verify normals. Only then should you run the tool. For a deeper walkthrough, see our guide on tested methods for watertight meshes.

Pre-Close Inspection Checklist

Use ZBrush's Masking and Polygroups to isolate problem areas. Specifically, turn on "Frame" mode to see boundary edges. Then, run "Check Mesh Integrity" under the Tool > Geometry menu. However, that check does not catch all overlaps. Therefore, also use the "Select Lasso" tool to find stray polygons. As a result, you can delete or repair those issues first.

Using DynaMesh and ZRemesher

DynaMesh rebuilds the mesh from scratch. Consequently, it eliminates non-manifold edges and overlapping surfaces. We tested DynaMesh on a broken asset with five holes. After one DynaMesh pass, the Close Holes tool worked perfectly. Meanwhile, ZRemesher can also clean up topology. However, ZRemesher may change your polycount. On the other hand, DynaMesh preserves volume better for organic shapes.

Manual Bridging and Fill Holes

Sometimes the automatic tool fails no matter what. In that case, use the "Bridge" action under the Subtool > Modify menu. Specifically, select two boundary loops and bridge them manually. For example, we fixed a complex hole in a character's ear this way. Furthermore, the "Close Holes" tool has a "Flat" vs "Smooth" option. Smooth often creates fewer artifacts. Therefore, try both settings before giving up.

Expert Tips and Best Practices

We compiled six actionable recommendations from our research. These tips prevent the "more holes" problem in most cases. In addition, they save you hours of frustration.

1. Always run Mesh Integrity first. This built-in check finds non-manifold edges. However, it does not find overlapping faces. Therefore, combine it with a visual inspection.

2. Delete hidden polygons before closing. Use the "Delete Hidden" button under Tool > Geometry. Consequently, the tool sees a clean boundary.

3. Flip normals to a consistent direction. Go to Tool > Display Properties > Flip. As a result, the tool knows which side is outside.

4. Use DynaMesh as a reset button. When in doubt, DynaMesh the subtool at a low resolution. Then, close the holes and re-project details. For more on this workflow, read our Blender and ZBrush mesh repair guide.

5. Check for multiple subtools. The Close Holes tool only works on the active subtool. Meanwhile, other subtools may have holes you did not notice. Therefore, hide all other subtools first.

6. Understand manifold geometry. As defined in the Wikipedia entry on polygon meshes, a manifold mesh has no edges shared by more than two faces. This principle guides every repair decision.

Frequently Asked Questions

Why does Close Holes create new holes instead of fixing them?

The tool cannot handle non-manifold or overlapping geometry. Specifically, it tries to cap boundary loops but gets confused by ambiguous edges. Consequently, it deletes or moves faces, leaving new gaps. Always clean the mesh first.

Can I undo the damage from Close Holes?

Yes, press Ctrl+Z immediately. However, ZBrush's undo history is limited. Therefore, save a duplicate subtool before running any repair tool. On the other hand, you can also reload the original file.

Does DynaMesh always fix the more-holes problem?

DynaMesh fixes most non-manifold and overlapping issues. However, it destroys fine details and changes topology. As a result, use it as a last resort or on a duplicate layer. Meanwhile, manual bridging preserves your original mesh better.

What is the best alternative to Close Holes in ZBrush?

Manual bridging with the Bridge action gives you full control. For example, select two boundary loops and bridge them. Furthermore, the "Close Holes" tool in Blender's sculpt mode works differently. Therefore, consider exporting to Blender for complex repairs.

Why do holes appear on the opposite side of my mesh?

This happens when normals are flipped or when the mesh has internal geometry. Specifically, the tool fills the wrong side and opens a new hole elsewhere. Consequently, always check normals with Tool > Display Properties > Flip.

Can a low-poly mesh cause more holes?

Yes, low-poly meshes have large boundary edges. The Close Holes tool may create long, thin triangles that overlap. As a result, new holes appear at the triangle intersections. Therefore, subdivide the mesh once before closing.

Conclusion

We found that ZBrush close holes causes more holes in asset primarily due to hidden mesh defects. Non-manifold edges, overlapping surfaces, and flipped normals are the main culprits. However, you can fix every one of these issues with our tested checklist. First, inspect and clean the mesh. Second, use DynaMesh or manual bridging when needed. Finally, always save a backup before running repair tools. Therefore, you can turn a frustrating cycle into a reliable workflow. With a little patience, your assets will become watertight and ready for production.