public override FP ComputeSubmergedArea(ref FPVector2 normal, FP offset, ref Transform xf, out FPVector2 sc)
{
sc = FPVector2.zero;
FPVector2 p = MathUtils.Mul(ref xf, Position);
FP l = -(FPVector2.Dot(normal, p) - offset);
if (l < -Radius + Settings.Epsilon)
{
//Completely dry
return(0);
}
if (l > Radius)
{
//Completely wet
sc = p;
return(Settings.Pi * _2radius);
}
//Magic
FP l2 = l * l;
FP area = _2radius * (FP)((FPMath.Asin((l / Radius)) + FPMath.PiOver2) + l * FPMath.Sqrt(_2radius - l2));
// TODO - PORT
//FP com = -2.0f / 3.0f * (FP)Math.Pow(_2radius - l2, 1.5f) / area;
FP com = new FP(-2) / new FP(3) * (FP)Math.Pow((_2radius - l2).AsFloat(), 1.5f) / area;
sc.x = p.x + normal.x * com;
sc.y = p.y + normal.y * com;
return(area);
}