solving_ik.md

Solving IK without the dataset

You can solve IK for any arbitrary pose by setting the desired transforms manually. First you have to initialize the WBIKConfig object and set the following parameters:

1. mjcf_path - Path to the MJCF model of the robot
2. body_to_model_map - Map of body aliases to mjcf names. For details on how to define this mapping see Adding new datasets

wbik_params = WBIKConfig()
wbik_params.mjcf_path = "path/to/your/model.xml"
wbik_params.body_to_model_map = {
        "root": "",
        "left_hip": "",
        "right_hip": "",
        "left_knee": "",
        "right_knee": "",
        "left_foot": "",
        "right_foot": "",
        "left_hand": "",
        "right_hand": "",
        "left_elbow": "",
        "right_elbow": "",
        "left_shoulder": "",
        "right_shoulder": "",
    }
# .... You can edit task weights here
    
wbik = WBIKSolver(wbik_params=wbik_params)
wbik.set_target_transform("root", root_position, root_rotation)
wbik.set_target_transform("right_foot", right_foot_position, right_foot_rotation)
wbik.set_target_transform("left_foot", left_foot_position, left_foot_rotation)
wbik.set_target_transform("left_knee", left_knee_position)
wbik.set_target_transform("right_knee", right_knee_position)
wbik.set_target_transform("left_elbow", left_elbow_position)
wbik.set_target_transform("right_elbow", right_elbow_position)
wbik.set_target_transform("left_hand", left_hand_position)
wbik.set_target_transform("right_hand", right_hand_position)

No you can solve the IK. wbik.solve() will return a PoseData object

pose_data = wbik.solve() 
pose_data.transforms # list of BodyTransform objects
pose_data.q # np.ndarray of the minimal coordinates of the robot model
pose_data.body_aliases # map of body names to mjcf names
pose_data.model_root # name of the root body in mjcf model
pose_data.contacts # Contact states are update on every consecutive solve call
pose_data.position_error # absolute position error of all links wrt to the reference
pose_data.dt # integration step duration in seconds
pose_data.joint_order # order of the joints in the q vector

Solving IK with the dataset

Check out the CMU and AMASS examples for more details on how to use the dataset to solve IK.