/*
* Returns true if:
* The speed of eye movement does not exceed (radiusMM / ConfigManager.fixationMinDurationMs) millimeters/seconds
* measured over a total duration of minMs.
*
* This function should be called when it's acceptable for the eyes to continue moving slowly and still count it as fixation.
*/
public static bool IsMovingFixation(int minMs, int radiusMm)
{
if (warpPointer == null)
{
return(false);
}
List <Point> rawGazePoints = warpPointer.GetGazeHistory();
if (rawGazePoints == null || rawGazePoints.Count == 0)
{
return(false);
}
int sampleRate = warpPointer.GetSampleRate();
//total number of samples that should be meet the fixation width criteria
int lookbackSampleCount = (int)Math.Max(1, sampleRate * minMs / 1000);
if (lookbackSampleCount > rawGazePoints.Count)
{
return(false);
}
//moving window samples amount
int windowSampleCount = Math.Max(sampleRate * ConfigManager.fixationMinDurationMs / 1000, 1);
int stopIndex = Math.Max(0, rawGazePoints.Count - windowSampleCount);
//Get average of the first window
//We start at the most recent point in history
Point runningSum = new Point(0, 0);
Point runningAvg = new Point(0, 0);
for (int i = rawGazePoints.Count - 1; i >= stopIndex; i--)
{
runningSum.X += rawGazePoints[i].X;
runningSum.Y += rawGazePoints[i].Y;
}
runningAvg.X = runningSum.X / windowSampleCount;
runningAvg.Y = runningSum.Y / windowSampleCount;
//Check that each point in the current window meets the fixation width criteria
for (int i = rawGazePoints.Count - 1; i >= stopIndex; i--)
{
if (PointHelper.GetPointDistance(runningAvg, rawGazePoints[i]) > ScreenPixelHelper.ConvertMmToPixels(radiusMm))
{
return(false); //this point is too far from the avg
}
}
//slide window until we complete lookbackSampleCount many
stopIndex = Math.Max(0, rawGazePoints.Count - lookbackSampleCount);
int lowerIndex = rawGazePoints.Count - 1 - windowSampleCount;
while (lowerIndex >= stopIndex)
{
int upperIndex = lowerIndex + windowSampleCount;
//Remove one point from window
runningSum.X -= rawGazePoints[upperIndex].X;
runningSum.Y -= rawGazePoints[upperIndex].Y;
//Add another point to the window
runningSum.X += rawGazePoints[lowerIndex].X;
runningSum.Y += rawGazePoints[lowerIndex].Y;
//Recalculate avg
runningAvg.X = runningSum.X / windowSampleCount;
runningAvg.Y = runningSum.Y / windowSampleCount;
//See if newest point is within the average
if (PointHelper.GetPointDistance(runningAvg, rawGazePoints[lowerIndex]) > ScreenPixelHelper.ConvertMmToPixels(radiusMm))
{
return(false); //this point is too far from the avg
}
lowerIndex--;
}
//Been through lookbackSampleCount and all of them according to the moving window are within fixation width requirement
return(true);
}
