add s-bend example and surface config

examples/04_sbends_and_radii.py

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+from shapely.geometry import Polygon
+
+from inire.geometry.collision import CollisionEngine
+from inire.geometry.primitives import Port
+from inire.router.astar import AStarRouter
+from inire.router.config import CostConfig, RouterConfig
+from inire.router.cost import CostEvaluator
+from inire.router.danger_map import DangerMap
+from inire.router.pathfinder import PathFinder
+from inire.utils.visualization import plot_routing_results
+
+
+def main() -> None:
+    print("Running Example 04: S-Bends and Multiple Radii...")
+
+    # 1. Setup Environment
+    bounds = (0, 0, 150, 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)
+    evaluator = CostEvaluator(
+        engine, 
+        danger_map,
+        unit_length_cost=1.0,
+        greedy_h_weight=1.2,
+    )
+    
+    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
+    )
+    
+    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.
+    netlist = {
+        "large_bend_net": (Port(10, 10, 0), Port(140, 80, 0)),
+        "sbend_net": (Port(10, 50, 0), Port(70, 70, 0)), 
+    }
+    net_widths = {"large_bend_net": 2.0, "sbend_net": 2.0}
+
+    # 4. Route
+    results = pf.route_all(netlist, net_widths)
+
+    # 5. Check Results
+    for nid, res in results.items():
+        status = "Success" if res.is_valid else "Failed"
+        print(f"{nid}: {status}, collisions={res.collisions}")
+
+    # 6. Visualize
+    fig, ax = plot_routing_results(results, obstacles, bounds)
+    fig.savefig("examples/sbends_radii.png")
+    print("Saved plot to examples/sbends_radii.png")
+
+
+if __name__ == "__main__":
+    main()