WorldGen: smoother TSDF

docs/VALIDATION.md

@@ -81,15 +81,15 @@ Default mesh is now a **voxel signed-distance field + marching cubes**
 (`worldgen_mesh.py --method voxel`):
 
 ```text
-voxel-res 0.25, voxel-stride 4, median 5, trim-poles 0.02
-52k verts / 103k tris
+voxel-res 0.25, voxel-stride 4, median 5, trim-poles 0.02, voxel-smooth 2.5
+50k verts / 98k tris
 ~3.3 s at 1024x512
 i2s end-to-end 20 steps: ~70 s (vs 61.5 s shell)
 ```
 
-The median filter + pole trim removes the small top tab; the left depth
-discontinuity still folds into a second surface. This is a large improvement
-over the needle-like shell but not a fully clean reconstruction.
+Median filtering, pole trimming and a 2.5-voxel Gaussian smoothing remove the
+top tab and reduce the left fold. The left crescent is still visible, so this
+is a large improvement over the needle shell but not a perfect reconstruction.
 
 Poisson/Ball/Alpha are available but were not better: