updated parameters and updated visualization function to better display the flow

visualization.py

@@ -1,4 +1,5 @@
 import sys
+import numpy as np
 import pandas as pd
 import matplotlib.pyplot as plt
 from matplotlib.animation import FuncAnimation
@@ -9,6 +10,20 @@ if len(sys.argv) < 2:
 df = pd.read_csv(sys.argv[1])
 frames = sorted(df["time"].unique())
 
+# Replace p.e with direction-of-next-hop: where the ped actually moves to next frame.
+# Falls back to p.e for the last frame and for teleport jumps.
+df = df.sort_values(["id", "time"]).reset_index(drop=True)
+df["dx"] = df.groupby("id")["x"].shift(-1) - df["x"]
+df["dy"] = df.groupby("id")["y"].shift(-1) - df["y"]
+mag = np.sqrt(df["dx"]**2 + df["dy"]**2)
+TELEPORT_THRESHOLD = 5.0  # any per-step jump larger than this is the teleport, not motion
+fallback = (mag > TELEPORT_THRESHOLD) | mag.isna() | (mag < 1e-9)
+df.loc[fallback, "dx"] = df.loc[fallback, "p.e.x"]
+df.loc[fallback, "dy"] = df.loc[fallback, "p.e.y"]
+mag = np.sqrt(df["dx"]**2 + df["dy"]**2).replace(0, 1.0)
+df["dx"] = df["dx"] / mag
+df["dy"] = df["dy"] / mag
+
 fig, ax = plt.subplots(figsize=(10, 2.2))
 ax.set_xlim(0, 50); ax.set_ylim(0, 10)
 ax.set_aspect("equal"); ax.set_facecolor("white")
@@ -39,13 +54,13 @@ def update(t):
     # Draw fresh arrows each frame
     arrow_scale = 1.5  # Tune this to change arrow length visually
     if len(w):
-        q_white = ax.quiver(w["x"], w["y"], w["p.e.x"], w["p.e.y"],
+        q_white = ax.quiver(w["x"], w["y"], w["dx"], w["dy"],
                             color="black", angles="xy", scale_units="xy",
                             scale=1/arrow_scale, width=0.003,
                             headwidth=4, headlength=5, zorder=3)
         quivers.append(q_white)
     if len(b):
-        q_black = ax.quiver(b["x"], b["y"], b["p.e.x"], b["p.e.y"],
+        q_black = ax.quiver(b["x"], b["y"], b["dx"], b["dy"],
                             color="gray", angles="xy", scale_units="xy",
                             scale=1/arrow_scale, width=0.003,
                             headwidth=4, headlength=5, zorder=3)
@@ -57,7 +72,7 @@ def update(t):
 anim = FuncAnimation(fig, update, frames=frames, interval=50, blit=False)
 
 if len(sys.argv) >= 3:
-    anim.save(sys.argv[2], writer="ffmpeg", fps=20)
+    anim.save(sys.argv[2], writer="ffmpeg", fps=5)
     print(f"Saved {sys.argv[2]}")
 else:
     plt.show()