Upload centerline_extraction.py

centerline_extraction.py

@@ -2141,28 +2141,60 @@ def _deduplicate_bifurcation_points(bif_points, threshold_mm=5.0):
 def _orient_artery_segments(segments):
     """Ensure artery (non-Aorta) segments are ordered bifurcation → endpoint.
 
-    After splitting at bifurcation points, one end of each artery segment
-    is touching an Aorta segment (the bifurcation end) and the other is
-    the branch tip.  We want the first point to be at the bifurcation
-    so that the frontend tangent (next − prev) naturally points away from
-    the aorta.
-
-    Heuristic: the bifurcation end has a larger radius (closer to the
-    trunk).  If the first point's radius is *smaller* than the last
-    point's, reverse the segment.
+    Strategy (preferred): the bifurcation end of a branch is physically
+    touching an Aorta segment endpoint (they share the same VMTK network
+    node, so the distance is ≈ 0 mm).  We check both ends of each artery
+    segment against all Aorta segment endpoints; whichever end is closest
+    to any aorta endpoint is the bifurcation end and must come first.
+
+    Fallback: if no Aorta segments exist yet (very rare), fall back to the
+    radius heuristic — the bifurcation end is typically thicker.
+
+    Why not radius alone?  After 1 mm resampling the Voronoi radius at the
+    resampled endpoints can be slightly different from the exact bifurcation
+    radius, causing the heuristic to flip segments that should stay and
+    vice-versa.  Proximity to an Aorta endpoint is exact (same VTK point ID
+    → same x,y,z coordinates) and therefore completely reliable.
     """
+    # Collect all Aorta segment endpoints (first and last point of each Aorta seg)
+    aorta_eps = []
     for seg in segments:
-        if seg['label'] == 'Aorta':
+        if seg.get('label') != 'Aorta':
             continue
-        pts = seg['points']
+        pts = seg.get('points', [])
+        if not pts:
+            continue
+        aorta_eps.append(pts[0])
+        if len(pts) > 1:
+            aorta_eps.append(pts[-1])
+
+    for seg in segments:
+        if seg.get('label') == 'Aorta':
+            continue
+        pts = seg.get('points', [])
         if len(pts) < 2:
             continue
-        # Compare radii at both ends.  Bifurcation end is thicker.
-        r_first = pts[0]['radius']
-        r_last  = pts[-1]['radius']
-        if r_first < r_last:
-            # First point is the thin (tip) end → reverse so bif comes first
-            pts.reverse()
+
+        if aorta_eps:
+            # Proximity check: which end is closest to any Aorta endpoint?
+            p0, p_last = pts[0], pts[-1]
+            min_dist_start = min(
+                (p0['x'] - ae['x']) ** 2 + (p0['y'] - ae['y']) ** 2 + (p0['z'] - ae['z']) ** 2
+                for ae in aorta_eps
+            )
+            min_dist_end = min(
+                (p_last['x'] - ae['x']) ** 2 + (p_last['y'] - ae['y']) ** 2 + (p_last['z'] - ae['z']) ** 2
+                for ae in aorta_eps
+            )
+            # If the END is closer to the aorta, the segment is backwards → reverse it
+            if min_dist_end < min_dist_start:
+                pts.reverse()
+        else:
+            # Fallback: radius heuristic (bifurcation end is thicker)
+            r_first = pts[0]['radius']
+            r_last  = pts[-1]['radius']
+            if r_first < r_last:
+                pts.reverse()
 
 
 # Build Frontend response JSON