// Load the rigs and their animations on to this screen.
	public void LoadRigs (int[] characterIndices, HandlePositionPairSet[][] animations) {
		Transform container = transform.Find ("Stage");
		container.DestroyAllChildren ();
		rigs = new Dictionary<int, PosingController> ();
		for (int i = 0; i < characterIndices.Length; i++) {
			int characterIndex = characterIndices [i];

			// Display the bird and its animation.
			Bird bird = GameController.GetBird (characterIndex);
			PosingController rig = Instantiate (bird.rig);
			rig.transform.SetParent (container);
			rig.transform.localScale = Vector3.one;
			rig.transform.position = new Vector3 (i * characterSpacing, 0, 0);
			rig.PlayAnimation (animations [i]);
			rigs.Add (characterIndex, rig);

			// Display the select mate button.
			Button selectButton = Instantiate (selectMateButtonPrefab);
			selectButton.transform.SetParent (container);
			selectButton.transform.localScale = Vector3.one;
			selectButton.transform.position = new Vector3 (i * characterSpacing, selectMateButtonPrefab.transform.position.y, 0);
			selectButton.onClick.AddListener (() => OnSelectMate (characterIndex));
		}
		cameraEndBound = characterSpacing * (characterIndices.Length - 1);
	}
	// Collect the set of handle position pairs.
	public HandlePositionPairSet CollectHandlePositions () {
		HandlePositionPairSet pairs = new HandlePositionPairSet ();
		for (int i = 0; i < handles.Length; i++) {
			HandleController handle = handles [i];
			pairs.handlePositionPairs.Add (
				new HandlePositionPair {
					handleID = handle.id,
					position = handle.transform.position,
				}
			);
		}
		return pairs;
	}
	// Play an animation given a bunch of handle-position pairs and frames.
	public void PlayAnimation (HandlePositionPairSet[] pairs) {

		// Can't see handles while playing.
		SetAllHandlesVisible (false);

		// Check if there are actually pairs to work with.
		if (pairs == null || pairs.Length <= 0) {
			return;
		}

		// Copy pairs and start playing.
		playingKeyframes = pairs;
		playing = true;
	}