Quaternion.LookRotation() What does it do?

Unity Engine
1

Hi I have an embarrassingly simple problem that I just can’t solve.

I am using Unity3D as a client and I have a server that uses an External 3D Math Library that includes Quaternions but does not included the method “Quaternion.LookRotation()” or anything that I can find like it.

So what does Quaternion.LookRotation() do exactly?
The best I could come up with after searching around the interwebs was…

Vector3 dir = (Target.position - transform.position);
Vector3 axis = Vector3.Cross(Vector3.up, dir.normalized);
float angle = Vector3.Dot(Vector3.right, dir.normalized);

rotationToTarget = Quaternion.AngleAxis(angle, axis);
//rotationToTarget = Quaternion.LookRotation(dir);

//transform.rotation *= rotationToTarget
transform.rotation = Quaternion.Slerp(transform.rotation, rotationToTarget, Time.deltaTime);

But this just rotates to ‘identity’?
I am missing something obvious and simple I know I am…

Not ‘strictly’ a Unity3D question exactly I know, but currently I have spent 3 days trying to work this out and it seems like it should be so simple.

2

I’m not sure what the code you posted is supposed to do, but it doesn’t make any sense to me (and I think it’s safe to say it’s not what LookRotation() does).

LookRotation() basically does the same thing as a typical ‘look-at’ view transform function, except that there’s no translation involved (since we’re just dealing with a quaternion), and the transform is not inverted.

The code might look something like this (untested):

vector3 z = direction.normalize();
vector3 x = cross(up, z).normalize();
vector3 y = cross(z, x);
return quaternion_from_basis_vectors(x, y, z);

The ‘quaternion from basis vectors’ part is basically a matrix-to-quaternion conversion, which is a little less straightforward than converting the other way, but is nevertheless fairly well documented online and elsewhere.