PyBullet: added preliminary DART and MuJoCo backend files, MuJoCo can loadMJCF, stepSimulation and getBasePositionAndOrientation, DART is empty.

PyBullet: add 2d biped example.,

examples/pybullet/examples/biped2d_pybullet.py

@@ -0,0 +1,40 @@
+import pybullet as p
+import pybullet_data
+import os
+import time
+GRAVITY = -9.8
+dt = 1e-3
+iters=2000
+
+physicsClient = p.connect(p.GUI)
+p.setAdditionalSearchPath(pybullet_data.getDataPath())
+p.resetSimulation()
+#p.setRealTimeSimulation(True)
+p.setGravity(0,0,GRAVITY)
+p.setTimeStep(dt)
+planeId = p.loadURDF("plane.urdf")
+cubeStartPos = [0,0,1.13]
+cubeStartOrientation = p.getQuaternionFromEuler([0.,0,0])
+botId = p.loadURDF("biped/biped2d_pybullet.urdf",
+        cubeStartPos,
+        cubeStartOrientation) 
+ 
+#disable the default velocity motors 
+#and set some position control with small force to emulate joint friction/return to a rest pose
+jointFrictionForce=1
+for joint in range (p.getNumJoints(botId)):
+	p.setJointMotorControl2(botId,joint,p.POSITION_CONTROL,force=jointFrictionForce)
+
+#for i in range(10000):     
+#     p.setJointMotorControl2(botId, 1, p.TORQUE_CONTROL, force=1098.0)
+#     p.stepSimulation()
+#import ipdb
+#ipdb.set_trace()
+import time
+p.setRealTimeSimulation(1)
+while (1):
+    #p.stepSimulation()
+    #p.setJointMotorControl2(botId, 1, p.TORQUE_CONTROL, force=1098.0)
+    p.setGravity(0,0,GRAVITY)
+    time.sleep(1/240.)
+time.sleep(1000)