Three.js CSG Geometry Issue in r148

I understand you're experiencing visual artifacts (gaps/splits) in your CSG (Constructive Solid Geometry) operations after upgrading from Three.js r147 to r148 when using the three-bvh-csg library.

While the provided context doesn't specifically address this issue, I can offer some insights based on the information you've shared:

Potential Causes

Your suspicion about changes to vertex merging in BufferGeometryUtils or other internal Three.js updates is reasonable. These types of visual artifacts (gaps that appear at certain zoom levels) often indicate:

1. Precision issues in geometry calculations
2. Changes to vertex merging thresholds
3. Modifications to how normals are calculated at geometry intersections

Possible Solutions

Here are some approaches you might try:

1. Check for library compatibility: Ensure the three-bvh-csg library is compatible with Three.js r148. The library might need an update to accommodate changes in the core Three.js code.

2. Adjust merging parameters: If the library exposes any parameters for controlling vertex merging tolerance, try adjusting these values.

3. Apply post-processing: After the CSG operation, you could try:

   • Merging vertices with a custom tolerance
   • Recalculating normals
   • Using a smoothing pass on the resulting geometry

4. Temporary downgrade: If this functionality is critical, consider temporarily reverting to r147 until a solution is found.

5. Contact the library author: Since this appears to be a compatibility issue with a specific library, reaching out to @gkjohnson directly might be the most efficient approach.

Since this issue appears to be related to a specific third-party library's interaction with Three.js rather than a core Three.js feature, you might want to check the library's issue tracker or create a new issue there with your findings.