public static float LipCornerCoefficient(Vector3[] landmarks, ARCoreFaceMeshLandmark lipCornerLandmark, float min, float max)
{
var upperLip = (landmarks[(int)ARCoreFaceMeshLandmark.UpperLipLeft] + landmarks[(int)ARCoreFaceMeshLandmark.UpperLipRight]) * 0.5f;
var corner = landmarks[(int)lipCornerLandmark];
var chin = landmarks[(int)ARCoreFaceMeshLandmark.ChinMiddle];
// when you open your mouth wide, the distance from a lip corner to chin increases,
// and the distance from your upper lip to your chin also increases. This allows
// us to account for the first difference in a pretty stable way.
var halfUpperLipToChinDistance = Vector3.Distance(upperLip, chin) * 0.5f;
var distance = Vector3.Distance(corner, chin) - halfUpperLipToChinDistance;
return(CoefficientUtils.FromDistance(distance, min, max));
}
public static float EyebrowRaiseCoefficient(Vector3[] landmarks, ARCoreFaceMeshLandmark outer, ARCoreFaceMeshLandmark inner,
ARCoreFaceMeshLandmark outerEye, float min, float max)
{
var innerBrow = landmarks[(int)inner];
var outerBrow = landmarks[(int)outer];
var eyeOuter = landmarks[(int)outerEye];
var noseBridge = landmarks[(int)ARCoreFaceMeshLandmark.NoseBridge];
var bridgeToInnerBrow = Vector3.Distance(innerBrow, noseBridge);
var outerBrowToOuterEye = Vector3.Distance(outerBrow, eyeOuter);
// we mostly base this on the distance from outer brow to outer eye, which works ok on its own
// introducing a bit of weight from the distance between nose bridge and inner eyebrow
// makes this more accurate across all possible brow raises and across different faces
const float innerBrowWeight = 0.25f;
const float outerBrowWeight = 0.75f;
var distance = outerBrowToOuterEye * outerBrowWeight + bridgeToInnerBrow * innerBrowWeight;
return(CoefficientUtils.FromDistance(distance, min, max));
}