MuJoCo VR Mocap Hand Example

The mocap hand points offer a way to mimic users hand pose with MuJoCo mocap points, allowing for control over virtual hands in a MuJoCo environment.

Mocap Point API

By default any mocap body specified in the MuJoCo XML file will become a movable mocap point in the VR environment. In order to control specific mocap points with hand joints, we follow XR Hand Naming Conventions, where any mocap body with the same naming convention will be linked to that joint:

"{joint}-{left | right}" where joint is the name of the joint and left or right specifies the side of the hand.

Hand joint	Index	Hand joint (continue)	Index
wrist	0	middle-finger-phalanx-distal	13
thumb-metacarpal	1	middle-finger-tip	14
thumb-phalanx-proximal	2	ring-finger-metacarpal	15
thumb-phalanx-distal	3	ring-finger-phalanx-proximal	16
thumb-tip	4	ring-finger-phalanx-intermediate	17
index-finger-metacarpal	5	ring-finger-phalanx-distal	18
index-finger-phalanx-proximal	6	ring-finger-tip	19
index-finger-phalanx-intermediate	7	pinky-finger-metacarpal	20
index-finger-phalanx-distal	8	pinky-finger-phalanx-proximal	21
index-finger-tip	9	pinky-finger-phalanx-intermediate	22
middle-finger-metacarpal	10	pinky-finger-phalanx-distal	23
middle-finger-phalanx-proximal	11	pinky-finger-tip	24
middle-finger-phalanx-intermediate	12	-	-

python

'<body mocap="true" name="middle-finger-phalanx-proximal-right" pos="0.347 -0.012 1.01" quat="0 -0.7071 -0.7071 0">'

Now, to get the mujoco updates, we can listen to the ON_MUJOCO_FRAME event.

python

@app.add_handler("ON_MUJOCO_FRAME")
async def on_mujoco_frame(event: ClientEvent, sess: VuerSession):
    print("ON_MUJOCO_FRAME", event)

You should get events that looks like these:

and the main session handler.

python

@app.spawn(start=True)
async def main(sess: VuerSession):
    # here we setup the staging area. Use Fog to simulate MuJoCo's
    # default style.
    sess.set @ Scene(
        # grid=False,
        bgChildren=[
            Fog(color=0x2C3F57, near=10, far=20),
            Hands(),
            Sphere(
                args=[50, 10, 10],
                materialType="basic",
                material=dict(color=0x2C3F57, side=1),
            ),
        ],
    )
    await sleep(0.0005)
    sess.upsert @ MuJoCo(

        HandActuator(key="pinch-on-squeeze"),
        key="franka-gripper",
        src=asset_pref + "scene.xml",
        assets=[asset_pref + fn for fn in ASSETS_LIST],
        useLights=True,
        timeout=1000000,
        scale=0.1,
    )

    await sleep(100.0)