add Human3.6M support for deep_mimic env

examples/pybullet/gym/pybullet_envs/deep_mimic/mocap/quaternion.py

@@ -0,0 +1,30 @@
+import numpy as np
+
+def qrot(q, v):
+    """
+    Rotate vector(s) v about the rotation described by quaternion(s) q.
+    Expects a tensor of shape (*, 4) for q and a tensor of shape (*, 3) for v,
+    where * denotes any number of dimensions.
+    Returns a tensor of shape (*, 3).
+    """
+    assert q.shape[-1] == 4
+    assert v.shape[-1] == 3
+    assert q.shape[:-1] == v.shape[:-1]
+
+    qvec = q[..., 1:]
+
+    uv = np.cross(qvec, v)
+    uuv = np.cross(qvec, uv)
+    
+    return (v + 2 * (q[..., :1] * uv + uuv))
+    
+def qinverse(q, inplace=False):
+    # We assume the quaternion to be normalized
+    if inplace:
+        q[..., 1:] *= -1
+        return q
+    else:
+        w = q[..., :1]
+        xyz = q[..., 1:]
+        return np.hstack((w, -xyz))
+