add DeepMimic helper utils

examples/pybullet/gym/pybullet_utils/math_util.py

@@ -0,0 +1,18 @@
+import numpy as np
+
+RAD_TO_DEG = 57.2957795
+DEG_TO_RAD = 1.0 / RAD_TO_DEG
+INVALID_IDX = -1
+
+def lerp(x, y, t):
+    return (1 - t) * x + t * y
+
+def log_lerp(x, y, t):
+    return np.exp(lerp(np.log(x), np.log(y), t))
+
+def flatten(arr_list):
+    return np.concatenate([np.reshape(a, [-1]) for a in arr_list], axis=0)
+
+def flip_coin(p):
+    rand_num = np.random.binomial(1, p, 1)
+    return rand_num[0] == 1