examples: (fixes #1146) Fix three-gpp-v2v-channel-example and plotting script

Pass tx params copy to ComputeSnr, to prevent pathloss to be incorrectly accumulated over time

examples/channel-models/three-gpp-v2v-channel-example.cc

@@ -151,13 +151,10 @@ PrintGnuplottableBuildingListToFile(std::string filename)
         NS_LOG_ERROR("Can't open file " << filename);
         return;
     }
-    uint32_t index = 0;
     for (auto it = BuildingList::Begin(); it != BuildingList::End(); ++it)
     {
-        ++index;
         Box box = (*it)->GetBoundaries();
-        outFile << "set object " << index << " rect from " << box.xMin << "," << box.yMin << " to "
-                << box.xMax << "," << box.yMax << std::endl;
+        outFile << box.xMin << " " << box.yMin << " " << box.xMax << " " << box.yMax << std::endl;
     }
 }
 
@@ -359,7 +356,7 @@ main(int argc, char* argv[])
 
     for (int i = 0; i < simTime / timeRes; i++)
     {
-        ComputeSnrParams params{txMob, rxMob, txParams, noiseFigure, txAntenna, rxAntenna};
+        ComputeSnrParams params{txMob, rxMob, txParams->Copy(), noiseFigure, txAntenna, rxAntenna};
         Simulator::Schedule(timeRes * i, &ComputeSnr, params);
     }
 

examples/channel-models/three-gpp-v2v-channel-example.py

@@ -0,0 +1,86 @@
+#!/bin/python3
+
+# Copyright (c) 2020, University of Padova, Dep. of Information Engineering, SIGNET lab
+# Copyright (c) 2025, Centre Tecnologic de Telecomunicacions de Catalunya (CTTC)
+#
+# SPDX-License-Identifier: GPL-2.0-only
+
+import matplotlib.animation as animation
+import matplotlib.patches as patches
+import matplotlib.pyplot as plt
+
+#
+#  Plot the traces generated by three-gpp-v2v-channel-example
+#
+import pandas as pd
+
+# Load the data
+df = pd.read_csv("example-output.txt", sep=r"\s+", comment="#")
+df = df.iloc[::10, :]
+
+# Column indices (adjust if needed)
+TIME = 0
+TX_X = 1
+TX_Y = 2
+RX_X = 3
+RX_Y = 4
+SNR = 6
+
+# Create the figure and subplots
+fig, (ax_map, ax_snr) = plt.subplots(1, 2, figsize=(12, 6))
+
+# Map plot config
+ax_map.set_xlim(-25, 600)
+ax_map.set_ylim(-25, 1000)
+ax_map.set_xlabel("X [m]")
+ax_map.set_ylabel("Y [m]")
+ax_map.set_aspect("equal")
+tx_circle = patches.Circle((0, 0), 5, color="blue", alpha=0.35)
+rx_circle = patches.Circle((0, 0), 5, color="red", alpha=0.35)
+ax_map.add_patch(tx_circle)
+ax_map.add_patch(rx_circle)
+
+# SNR plot config
+ax_snr.set_xlim(0, 40)
+ax_snr.set_ylim(-20, 100)
+ax_snr.set_xlabel("Time [s]")
+ax_snr.set_ylabel("SNR [dB]")
+ax_snr.grid(True)
+(snr_line,) = ax_snr.plot([], [], "k-")
+
+buildings = pd.read_csv("buildings.txt", sep=r"\s+", comment="#", header=None)
+building_patches = []
+for idx, row in buildings.iterrows():
+    x0, y0, x1, y1 = row
+    width = x1 - x0
+    height = y1 - y0
+    rect = patches.Rectangle((x0, y0), width, height, color="gray", alpha=0.5)
+    ax_map.add_patch(rect)
+    building_patches.append(rect)
+
+
+# Animation update function
+def update(frame):
+    row = df.iloc[frame]
+    tx_circle.set_center((row.iloc[TX_X], row.iloc[TX_Y]))
+    rx_circle.set_center((row.iloc[RX_X], row.iloc[RX_Y]))
+    snr_line.set_data(df.iloc[: frame + 1, TIME], df.iloc[: frame + 1, SNR])
+    ax_map.set_title(f"Time = {row.iloc[TIME]:.1f} s")
+    return tx_circle, rx_circle, snr_line
+
+
+# Run animation
+ani = animation.FuncAnimation(fig, update, frames=len(df), interval=0.001, blit=False)
+
+# Save animation
+ani.save("map.gif", writer="pillow")
+
+# Save final SNR plot separately
+plt.figure()
+plt.plot(df.iloc[:, TIME], df.iloc[:, SNR], "k-")
+plt.xlabel("Time [s]")
+plt.ylabel("SNR [dB]")
+plt.grid(True)
+plt.xlim(0, 40)
+plt.ylim(-20, 100)
+plt.savefig("snr.png")

examples/channel-models/three-gpp-v2v-channel-example.sh

@@ -1,57 +0,0 @@
-#!/bin/bash
-
-# Copyright (c) 2020, University of Padova, Dep. of Information Engineering, SIGNET lab
-#
-# SPDX-License-Identifier: GPL-2.0-only
-
-#
-#  Plot the traces generated by three-gpp-vehicular-channel-condition-model-example
-#
-
-cat >aa <<EOL
-set terminal gif animate delay 100
-set output 'map.gif'
-set view map
-set style fill transparent solid 0.5
-unset key
-set style fill  transparent solid 0.35 noborder
-set style circle radius 5
-
-do for [i=0:299] {
-  set multiplot layout 1,2
-    set zrange [i-1:i]
-    set xrange [-25:600]
-    set yrange [-25:1000]
-    set xlabel 'X [m]'
-    set ylabel 'Y [m]'
-    set xtics
-    set ytics
-    load 'buildings.txt'
-    splot 'example-output.txt' u 2:3:1 with circles lc rgb "blue", 'example-output.txt' u 4:5:1 with circles lc rgb "red"
-    set object 101 rect from -25,-25 to 1400,1000 fc rgb "white"
-    set xrange [i-0.001:i+0.001]
-    set yrange [i-0.001:i+0.001]
-    unset xlabel
-    unset ylabel
-    unset xtics
-    unset ytics
-    plot 'example-output.txt' using 1:1:1 with labels offset -10, 0, 'example-output.txt' using 1:1:6 with labels offset 10, 0
-    unset object 101
-  unset multiplot
-}
-
-reset
-set terminal png
-set output 'snr.png'
-set xlabel 'Time [s]'
-set ylabel 'SNR [dB]'
-set xtics
-set ytics
-set grid
-set xrange [0:40]
-set yrange [-20:100]
-plot 'example-output.txt' u 1:7 w l
-EOL
-gnuplot aa
-rm aa
-# rm out.txt