common: add BounceFilter

Author: adeebshihadeh

common/filter_simple.py

@@ -15,3 +15,20 @@ def update(self, x):
       self.initialized = True
       self.x = x
     return self.x
+
+
+class BounceFilter(FirstOrderFilter):
+  def __init__(self, x0, rc, dt, initialized=True, bounce=2):
+    self.velocity = FirstOrderFilter(0.0, 0.15, dt)
+    self.bounce = bounce
+    super().__init__(x0, rc, dt, initialized)
+
+  def update(self, x):
+    super().update(x)
+    scale = self.dt / (1.0 / 60.0)  # tuned at 60 fps
+    self.velocity.x += (x - self.x) * self.bounce * scale * self.dt
+    self.velocity.update(0.0)
+    if abs(self.velocity.x) < 1e-5:
+      self.velocity.x = 0.0
+    self.x += self.velocity.x
+    return self.x