diff --git a/trimesh/interval.py b/trimesh/interval.py
index 2c5aba7ec..73782d5bf 100644
--- a/trimesh/interval.py
+++ b/trimesh/interval.py
@@ -13,8 +13,8 @@
 
 def intersection(a: NDArray[float64], b: NDArray[float64]) -> NDArray[float64]:
     """
-    Given a pair of ranges, merge them in to
-    one range if they overlap at all
+    Given pairs of ranges merge them in to
+    one range if they overlap.
 
     Parameters
     --------------
@@ -27,7 +27,7 @@ def intersection(a: NDArray[float64], b: NDArray[float64]) -> NDArray[float64]:
     --------------
     inter : (2, ) or (2, 2) float
       The unioned range from the two inputs,
-      if not overlapping ptp will be zero.
+      if not `inter.ptp(axis=1)` will be zero.
     """
     a = np.array(a, dtype=np.float64)
     b = np.array(b, dtype=np.float64)
diff --git a/trimesh/path/segments.py b/trimesh/path/segments.py
index 960a89bf7..566be34ab 100644
--- a/trimesh/path/segments.py
+++ b/trimesh/path/segments.py
@@ -177,9 +177,11 @@ def clean(segments: NDArray[float64], digits: int = 10) -> NDArray[float64]:
     # collect new unified paramameters
     p, o, v = [], [], []
     for g in group_rows(np.column_stack((origins, vectors)), digits=digits):
+        # union the intervals sorting ourselves to skip the `sort(axis=1)` we did above
         group = param[g]
         u = interval.union(group[group[:, 0].argsort()], sort=False)
         p.extend(u)
+        # use the origins for the subsetted union
         o.extend(origins[g[: len(u)]])
         v.extend(vectors[g[: len(u)]])