GazeStabilizer.cs

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See LICENSE in the project root for license information.

using UnityEngine;

namespace HoloToolkit.Unity.InputModule
{
    public class GazeStabilizer : BaseRayStabilizer
    {
        [Tooltip("Number of samples that you want to iterate on.")]
        [Range(40, 120)]
        public int StoredStabilitySamples = 60;

        private Vector3 stablePosition;
        public override Vector3 StablePosition
        {
            get { return stablePosition; }
        }

        private Quaternion stableRotation;
        public override Quaternion StableRotation
        {
            get { return stableRotation; }
        }

        private Ray stableRay;
        public override Ray StableRay
        {
            get { return stableRay; }
        }

        private readonly VectorRollingStatistics positionRollingStats = new VectorRollingStatistics();

        private readonly VectorRollingStatistics directionRollingStats = new VectorRollingStatistics();

        private const float PositionStandardDeviationReset = 0.2f;

        private const float DirectionStandardDeviationReset = 0.1f;

        private const int MinimumSamplesRequiredToStabalize = 30;

        private const float UnstabalizedLerpFactor = 0.3f;

        private const float StabalizedLerpBoost = 10.0f;

        private void Awake()
        {
            directionRollingStats.Init(StoredStabilitySamples);
            positionRollingStats.Init(StoredStabilitySamples);
        }

        public override void UpdateStability(Vector3 gazePosition, Vector3 gazeDirection)
        {
            positionRollingStats.AddSample(gazePosition);
            directionRollingStats.AddSample(gazeDirection);

            float lerpPower = UnstabalizedLerpFactor;
            if (positionRollingStats.ActualSampleCount > MinimumSamplesRequiredToStabalize && // we have enough samples and...
                (positionRollingStats.CurrentStandardDeviation > PositionStandardDeviationReset || // the standard deviation of positions is high or...
                 directionRollingStats.CurrentStandardDeviation > DirectionStandardDeviationReset)) // the standard deviation of directions is high
            {
                // We've detected that the user's gaze is no longer fixed, so stop stabilizing so that gaze is responsive.
                //Debug.LogFormat("Reset {0} {1} {2} {3}", positionRollingStats.standardDeviation, positionRollingStats.standardDeviationsAway, directionRollignStats.standardDeviation, directionRollignStats.standardDeviationsAway);
                positionRollingStats.Reset();
                directionRollingStats.Reset();
            }
            else if (positionRollingStats.ActualSampleCount > MinimumSamplesRequiredToStabalize)
            {
                // We've detected that the user's gaze is fairly fixed, so start stabilizing.  The more fixed the gaze the less the cursor will move.
                lerpPower = StabalizedLerpBoost * (positionRollingStats.CurrentStandardDeviation + directionRollingStats.CurrentStandardDeviation);
            }

            stablePosition = Vector3.Lerp(stablePosition, gazePosition, lerpPower);
            stableRotation = Quaternion.LookRotation(Vector3.Lerp(stableRotation * Vector3.forward, gazeDirection, lerpPower));
            stableRay = new Ray(stablePosition, stableRotation * Vector3.forward);
        }
    }
}