Minor tweaks to starfield example

lordmauve · Apr 16, 2019 · 258946c · 258946c
1 parent f94e44c
commit 258946c
Showing 1 changed file with 10 additions and 4 deletions.
diff --git a/examples/basic/stars.py b/examples/basic/stars.py
@@ -6,6 +6,7 @@
 HEIGHT = 1000 * 9 // 16
 ACCEL = 1.0  # Warp factor per second
 DRAG = 0.71  # Fraction of speed per second
+TRAIL_LENGTH = 3
 MIN_WARP_FACTOR = 0.1
 BOUNDS = Rect(0, 0, WIDTH, HEIGHT)
 
@@ -17,12 +18,17 @@
 
 
 class Star:
+    __slots__ = (
+        'pos', 'vel', 'brightness',
+        'speed', 'prev_pos'
+    )
+
     def __init__(self, pos, vel):
         self.pos = pos
         self.vel = vel
         self.brightness = 10
         self.speed = math.hypot(*vel)
-        self.prev_pos = deque(maxlen=3)
+        self.prev_pos = deque(maxlen=TRAIL_LENGTH)
         self.prev_pos.append(self.pos)
 
     def set_pos(self, pos):
@@ -60,13 +66,13 @@ def update(dt):
         (warp_factor - MIN_WARP_FACTOR) * DRAG ** dt
     )
 
-    for _ in range(int(dt * 200)):
+    while len(stars) < 300:
         angle = random.uniform(-math.pi, math.pi)
         dx = math.cos(angle)
         dy = math.sin(angle)
         speed = 255 * random.uniform(0.3, 1.0) ** 2
 
-        d = random.uniform(0, 100)
+        d = random.uniform(25, 100)
         pos = centerx + dx * d, centery + dy * d
 
         v = speed * dx, speed * dy
@@ -85,7 +91,7 @@ def update(dt):
 
 
 # Jump-start the star field
-for _ in range(10):
+for _ in range(30):
     update(0.5)
 for _ in range(5):
     update(1 / 60)