Put the CoM back as the reference frame for the fragmentation movies

examples/Fragmentation/Fragmentation_Movie.py

@@ -38,7 +38,7 @@
 available_movie_styles = ["disruption_headon", "disruption_off_axis", "supercatastrophic_headon", "supercatastrophic_off_axis","hitandrun_disrupt", "hitandrun_pure", "merge"]
 movie_title_list = ["Head-on Disruption", "Off-axis Disruption", "Head-on Supercatastrophic", "Off-axis Supercatastrophic", "Hit and Run w/ Runner Disruption", "Pure Hit and Run", "Merge"]
 movie_titles = dict(zip(available_movie_styles, movie_title_list))
-num_movie_frames = 1200
+num_movie_frames = 1000
 
 # These initial conditions were generated by trial and error
 names = ["Target","Projectile"]
@@ -206,9 +206,17 @@ def update_plot(self, frame):
         def reference_frame(r_ref, v_ref, t):
             coord_pos = r_ref + v_ref * t 
             return coord_pos.values[0], coord_pos.values[1]
+
+        def center(Gmass, x, y):
+            x = x[~np.isnan(x)]
+            y = y[~np.isnan(y)]
+            Gmass = Gmass[~np.isnan(Gmass)]
+            x_com = np.sum(Gmass * x) / np.sum(Gmass)
+            y_com = np.sum(Gmass * y) / np.sum(Gmass)
+            return x_com, y_com 
 
         t, Gmass, rh, point_rad = next(self.data_stream(frame))
-        x_ref, y_ref = reference_frame(self.r_ref,self.v_ref, t)
+        x_ref, y_ref = center(Gmass, rh[:,0], rh[:,1]) 
         self.scatter_artist.set_offsets(np.c_[rh[:,0] - x_ref, rh[:,1] - y_ref])
         self.scatter_artist.set_sizes(point_rad**2)
         return self.scatter_artist,