Try to debug out-of-range index

Seems to be in the `color` tuple in set_light_hsv, but doesn't
show up in debugging.

interactions.py

@@ -74,18 +74,16 @@ fullsat = 254
 
 # --- control methods
 
-def set_light_hsv(edge, color):
-  if b != None:
-    b.set_light(
-      edges[edge].light_id,
-      {
-        'hue' : color[0]*lasthue,
-        'bri' : color[2]*fullbright,
-        'sat' : color[1]*fullsat
-      }
-    )
+def set_light_hsv(e, color, hit_bridge):
+  command = {
+    'hue' : color[0]*lasthue,
+    'bri' : color[2]*fullbright,
+    'sat' : color[1]*fullsat
+  }
+  if hit_bridge and b != None:
+    b.set_light(edges[e].light_id, command)
   rgb_color = tuple(255*c for c in colorsys.hsv_to_rgb(*color))
-  pygame.draw.aaline(screen, rgb_color, vertices[vertex_adj[edge][0]], vertices[vertex_adj[edge][1]])
+  pygame.draw.aaline(screen, rgb_color, vertices[vertex_adj[e][0]], vertices[vertex_adj[e][1]])
 
 # === interaction parameters ===
 
@@ -103,6 +101,9 @@ drain_rate = 0.1
 charge = 12*[0]
 current = 30*[0]
 
+last_litness = 30*[float("inf")]
+change_threshold = 0.05
+
 # === main loop ===
 
 def heat_evolution():
@@ -127,6 +128,13 @@ def wave_evolution():
     for v in range(12):
       charge[v] *= 1 - drain_rate
 
+def set_wave_light(e, i):
+  litness = 1 - exp(-2*i*i)
+  hit_bridge = abs(litness - last_litness[e]) > change_threshold
+  set_light_hsv(e, (0.45 + litness*0.25, 1 - 0.5*litness*litness, litness), hit_bridge)
+  if hit_bridge:
+    last_litness[e] = litness
+
 def show_data(screen):
   energy = 0.5*(sum(q*q for q in charge) + inductance*sum(i*i for i in current))
   text = font.render('energy', True, (255, 255, 255))
@@ -175,8 +183,7 @@ if __name__ == '__main__':
     
     # show state
     for e in range(30):
-      litness = 1 - exp(-2*current[e]*current[e])
-      set_light_hsv(e, (0.45 + litness*0.25, 1 - 0.5*litness*litness, litness))
+      set_wave_light(e, current[e])
     
     # evolve state
     wave_evolution()