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Methods for saving/restoring simulation snapshots and manipulating joint state.

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saveState()

Capture a snapshot of the current simulation state. 
const snapshot = api.saveState();
Returns: StateSnapshot 
interface StateSnapshot {
  time: number;
  qpos: Float64Array;
  qvel: Float64Array;
  ctrl: Float64Array;
  act: Float64Array;
  qfrc_applied: Float64Array;
}

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restoreState(snapshot)

Restore a previously saved state. 
const snapshot = api.saveState();
// ... simulation runs ...
api.restoreState(snapshot); // Back to saved state
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snapshot
StateSnapshot
required
Snapshot from a previous saveState() call.

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setQpos(values)

Set all generalized positions. 
api.setQpos(new Float64Array([0, 0, 0.5, 1, 0, 0, 0])); // Free joint
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values
Float64Array | number[]
required
Array of length model.nq.

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getQpos()

Get all generalized positions. 
const qpos = api.getQpos(); // Float64Array of length nq
Returns: Float64Array

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setQvel(values)

Set all generalized velocities. 
api.setQvel(new Float64Array(model.nv).fill(0)); // Zero all velocities
​
values
Float64Array | number[]
required
Array of length model.nv.

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getQvel()

Get all generalized velocities. 
const qvel = api.getQvel(); // Float64Array of length nv
Returns: Float64Array

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applyKeyframe(nameOrIndex)

Apply a named or indexed keyframe from the model. 
api.applyKeyframe("home");  // By name
api.applyKeyframe(0);       // By index
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nameOrIndex
string | number
required
Keyframe name or index. Keyframes are defined in MJCF with <key> elements.

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getKeyframeNames()

Get all keyframe names. 
const names = api.getKeyframeNames(); // ["home", "pose1", ...]
Returns: string[]

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getKeyframeCount()

Get the number of keyframes. 
const count = api.getKeyframeCount(); // e.g., 3
Returns: number

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Example: Checkpoint System

function CheckpointControls() {
  const { api } = useMujoco();
  const snapshots = useRef<StateSnapshot[]>([]);

  return (
    <div>
      <button onClick={() => snapshots.current.push(api.saveState())}>
        Save Checkpoint ({snapshots.current.length})
      </button>
      <button onClick={() => {
        const snap = snapshots.current.pop();
        if (snap) api.restoreState(snap);
      }}>
        Restore
      </button>
    </div>
  );
}