'Spherical Billboarding' in Unity - unity3d

Question

I am making a 3D Planet roaming game. The Planet itself is 3D, but every object in the scene will be 2D. As the player walks around the planet, their rotation relative north changes, and thus, if objects are placed statically in the scene, sometimes objects will appear upside down. I basically want every object to be tangential to the sphere, while still maintaining its "uprightness".
Vector3 pos = transform.position;
Vector3 planetPos = Planet.transform.position;
Vector3 direction = (planetPos - pos).normalized; // Calculate Tangent
transform.rotation = Quaternion.Euler(direction);
transform.Rotate(new Vector3(90, 0, 0));
This code here rotates the object relative to the planet, but it doesnt maintain is orientation relative to the player.
How can I get the other objects to not appear upside down?
Spherical Billboarding

Answer 1

You could find the direction that the object was relative to the world, and make the object look at that.
public GameObject[] objs;
public Vector3 worldPos;
void Update()
{
foreach (GameObject obj in objs)
{
obj.transform.rotation = Quaternion.LookRotation(obj.transform.position - worldPos);
}
}
This disables physics, so you could add more:
public GameObject[] objs;
public Vector3 worldPos;
public gravityForce;
Vector3 gravity;
Quaternion look;
void Update()
{
foreach (GameObject obj in objs)
{
look = Quaternion.LookRotation(obj.transform.position - worldPos);
ChangeGravity(look, obj);
}
}
Rigidbody rb;
void ChangeGravity(Quaternion looking, GameObject obj)
{
gravity = new Vector3(looking.x, looking.y, looking.z);
gravity.Normalize();
gravity *= -gravityForce;
rb = obj.GetComponent<Rigidbody>();
rb.useGravity = false;
rb.AddForce(gravity);
}
These were untested, but the first one is much more likely to work.