more s-bend fixes and add docs

examples/04_sbends_and_radii.py

@@ -14,54 +14,43 @@ def main() -> None:
     print("Running Example 04: S-Bends and Multiple Radii...")
 
     # 1. Setup Environment
-    bounds = (0, 0, 150, 100)
+    bounds = (0, 0, 100, 100)
     engine = CollisionEngine(clearance=2.0)
     danger_map = DangerMap(bounds=bounds)
-    
-    # Create obstacles that force S-bends and turns
-    # Obstacle 1: Forces a vertical jog (S-bend)
-    obs1 = Polygon([(40, 20), (60, 20), (60, 60), (40, 60)])
-    
-    # Obstacle 2: Forces a large radius turn
-    obs2 = Polygon([(80, 0), (100, 0), (100, 40), (80, 40)])
-    
-    obstacles = [obs1, obs2]
-    for obs in obstacles:
-        engine.add_static_obstacle(obs)
-    
-    danger_map.precompute(obstacles)
-    
-    # 2. Configure Router with custom parameters (Directly via constructor)
+    danger_map.precompute([])
+
+    # 2. Configure Router
     evaluator = CostEvaluator(
-        engine, 
+        engine,
         danger_map,
         unit_length_cost=1.0,
-        greedy_h_weight=1.2,
+        greedy_h_weight=1.5,
     )
-    
+
+    # We want a 45 degree switchover for S-bend.
+    # Offset O = 2 * R * (1 - cos(theta))
+    # If R = 10, O = 5.86
+
     router = AStarRouter(
         evaluator,
-        node_limit=500000,
-        bend_radii=[10.0, 30.0],  # Allow standard and large bends
-        sbend_offsets=[-10.0, -5.0, 5.0, 10.0], # Allow larger S-bend offsets
-        sbend_radii=[20.0, 50.0], # Large S-bends
-        bend_penalty=10.0, # Lower penalty to encourage using the right bend
+        node_limit=50000,
+        bend_radii=[10.0, 30.0],
+        sbend_offsets=[5.0], # Use a simpler offset
+        sbend_radii=[10.0],
+        bend_penalty=10.0,
+        sbend_penalty=20.0,
+        snap_to_target_dist=50.0, # Large snap range
     )
-    
+
     pf = PathFinder(router, evaluator)
-    
+
     # 3. Define Netlist
-    # Net 1: Needs to S-bend around obs1 (gap at y=60-100? No, obs1 is y=20-60).
-    # Start at (10, 40), End at (140, 40).
-    # Obstacle 1 blocks 40-60. Net must go above or below.
-    # Obstacle 2 blocks 80-100 x 0-40.
-    
-    # Let's force a path that requires a large bend.
+    # start (10, 50), target (60, 55) -> 5um offset
     netlist = {
-        "large_bend_net": (Port(10, 10, 0), Port(140, 80, 0)),
-        "sbend_net": (Port(10, 50, 0), Port(70, 70, 0)), 
+        "sbend_only": (Port(10, 50, 0), Port(60, 55, 0)),
+        "multi_radii": (Port(10, 10, 0), Port(90, 90, 0)),
     }
-    net_widths = {"large_bend_net": 2.0, "sbend_net": 2.0}
+    net_widths = {"sbend_only": 2.0, "multi_radii": 2.0}
 
     # 4. Route
     results = pf.route_all(netlist, net_widths)
@@ -72,7 +61,7 @@ def main() -> None:
         print(f"{nid}: {status}, collisions={res.collisions}")
 
     # 6. Visualize
-    fig, ax = plot_routing_results(results, obstacles, bounds)
+    fig, ax = plot_routing_results(results, [], bounds)
     fig.savefig("examples/sbends_radii.png")
     print("Saved plot to examples/sbends_radii.png")