// https://stackoverflow.com/questions/1171849/finding-quaternion-representing-the-rotation-from-one-vector-to-another
public static Rot3f HalfWayVec(V3f from, V3f into)
{
if (from.Dot(into).ApproximateEquals(-1))
{
return(new Rot3f(0, from.AxisAlignedNormal()));
}
else
{
V3f half = Vec.Normalized(from + into);
QuaternionF q = new QuaternionF(Vec.Dot(from, half), Vec.Cross(from, half));
return(new Rot3f(q.Normalized));
}
}
public static Rot3f HalfWayQuat(V3f from, V3f into)
{
var d = Vec.Dot(from, into);
if (d.ApproximateEquals(-1))
{
return(new Rot3f(0, from.AxisAlignedNormal()));
}
else
{
QuaternionF q = new QuaternionF(d + 1, Vec.Cross(from, into));
return(new Rot3f(q.Normalized));
}
}
public static Rot3f Original(V3f from, V3f into)
{
var angle = from.AngleBetween(into);
if (angle < 1e-6f)
{
return(Rot3f.Identity);
}
else if (Constant.PiF - angle < 1e-6f)
{
return(new Rot3f(0, from.AxisAlignedNormal()));
}
else
{
V3f axis = Vec.Cross(from, into).Normalized;
return(Rot3f.Rotation(axis, angle));
}
}