add Human3.6M support for deep_mimic env

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

@@ -0,0 +1,26 @@
+import numpy as np 
+
+from quaternion import qrot, qinverse
+
+
+def normalize_screen_coordinates(X, w, h): 
+    assert X.shape[-1] == 2
+    # Normalize so that [0, w] is mapped to [-1, 1], while preserving the aspect ratio
+    return X/w*2 - [1, h/w]
+
+def image_coordinates(X, w, h):
+    assert X.shape[-1] == 2
+    # Reverse camera frame normalization
+    return (X + [1, h/w])*w/2
+
+def world_to_camera(X, R, t):
+    Rt = qinverse(R)
+    Q = np.tile(Rt, (*X.shape[:-1], 1))
+    V = X - t
+    return qrot(Q, V)
+    
+def camera_to_world(X, R, t):
+    Q = np.tile(R, (*X.shape[:-1], 1))
+    V = X
+    return qrot(Q, V) + t
+