How do I specify the position of one object relative to another object?

Questions & Answers
1

Let’s say, I have a position variable

private Vector3 leaderPosition;

I want to specify another vector

private Vector3 followerPosition;

I want this followerPosition to be 5 meters away from leaderPosition and at an angle of 45 degrees behind him (diagonally behind him like a V formation).

How do I do that? How do I manually set “followerPosition” to something like

followerPosition = leaderPosition + (something);

2

To find the position you would create a vector pointing behind the leader (negative forward):

Vector3 offset = -leader.transform.forward; //1m behind

Multiply that vector with the distance

offset *= 5; //5m behind

Rotate the offset

offset = Quaternion.AngleAxis(45, leader.transform.up) * offset; //45 degrees around the leaders up vector

All together

Vector3 offset = Quaternion.AngleAxis(45, leader.transform.up) * -leader.transform.forward * distance;
transform.position = leader.transform.position + offset;

Note: The order of multiplication is important here.

3

If you use

followerPosition = leaderPosition + (something);

your follower will be in the same world direction in relation to your leader; the follower may always be south-east of the leader, for example. That is unless you take the leader orientation into your calculations.

The easier way would be to use Transform.TransformPoint. That should take care of it for you.