Quick Glance - Stability/Smoothing Methods

Question

What is the difference between Method 1, Method 2, and Method 3 in Quick Glance?

How does it relate to the settings in QuickACCESS?

Answer 1

End Users and Resellers

Method 1 is a Heuristic, Time based filter.
Method 2 is a Weighted Previous Frame filter. In QuickACCESS this is Smart Stability. The description in the QuickACCESS documentation is as follows:

Uses an advanced filtering algorithm to move the cursor responsively but without jitter.

Method 3 is a Median Time based filter. In QuickACCESS this is Classic Stability. The description in the QuickACCESS documentation is as follows:

Uses the legacy smoothing algorithm as used previously in EyeTech's Quick Glance Application.

New users typically prefer the Smart Stability (Method 2). The default stability value is 60.

Users that have used Quick Glance since before 2012, have the most use with the Classic Stability, or Method 3.

Developers

Quick Glance to API name and number

 "No Filtering" // None                    = API 0
 "Method 1"     // Heuristic-Time          = API 4
 "Method 2";    // Weighted Previous Frame = API 5  - AKA "Smart" in QA
 "Method 3"     // Median-Time             = API 2  - AKA "Classic" in QA
 "not listed"   // Heuristic-Frames        = API 3
 "not listed"   // Median-Frames           = API 1

As documented in QuickLink 2 API Documentation

 QL_DEVICE_GAZE_POINT_FILTER_NONE                    = 0,
 QL_DEVICE_GAZE_POINT_FILTER_MEDIAN_FRAMES           = 1,
 QL_DEVICE_GAZE_POINT_FILTER_MEDIAN_TIME             = 2,
 QL_DEVICE_GAZE_POINT_FILTER_HEURISTIC_FRAMES        = 3,
 QL_DEVICE_GAZE_POINT_FILTER_HEURISTIC_TIME          = 4,
 QL_DEVICE_GAZE_POINT_FILTER_WEIGHTED_PREVIOUS_FRAME = 5

QL_DEVICE_GAZE_POINT_FILTER_NONE

No gaze point filtering will be done.

QL_DEVICE_GAZE_POINT_FILTER_MEDIAN_FRAMES

The median gaze point value over the last X number of frames, where X equals the value represented by the setting QL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE. This will produce a gaze point latency time of about (X / fps / 2) seconds.

QL_DEVICE_GAZE_POINT_FILTER_MEDIAN_TIME

The median gaze point value over the last X number of frames, where X is the number of frames gathered over twice the amount of milliseconds represented by the setting QL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE. This will produce a latency of about QL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE milliseconds.

QL_DEVICE_GAZE_POINT_FILTER_HEURISTIC_FRAMES

The heuristic filter uses different filtering strengths when the eye is moving and when it is fixating. When the eye is moving, very little filtering is done which results in very low latency. When the eye is fixating, large amounts of filtering are being done which greatly reduce the amount of jitter. During fixation, filtering is done over the last X number of frames where X equals the value represented by the settingQL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE.

QL_DEVICE_GAZE_POINT_FILTER_HEURISTIC_TIME

The heuristic filter uses different filtering strengths when the eye is moving and when it is fixating. When the eye is moving, very little filtering is done which results in very low latency. When the eye is fixating, large amounts of filtering are being done which greatly reduce the amount of jitter. During fixation, filtering is done over the last X number of frames where X equals the number of frames gathered over twice the amount of milliseconds represented by the setting QL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE. This produces approximately the same amount of latency during fixation for all frame rates.

QL_DEVICE_GAZE_POINT_FILTER_WEIGHTED_PREVIOUS_FRAME

The weighted previous frame mode filters the gaze point by summing the current weighted gaze point location and the previous weighted gazepoint location. The weights are based on the distance the current gaze point is away from the previous gaze point. The larger the distance, the greater the weight on the current gaze point. The smaller the distance, the greater the weight on the previous gaze point. This results in very low latency when the eye is moving and very low jitter when the eye is fixating. The value represented by the setting QL_SETTING_DEVICE_GAZE_POINT_FILTER_VALUE affects the rate at which the weighting changes from the previous gaze point to the current gaze point. Possible values range between 0 and 200.