Can relative velocity be calculated from relative direction vector

Questions & Answers
1

Let’s say i got direction vectors for an object relative to the camera looking at it as explained here

Is it possible for me to derive the relative velocity in those directions using the relative direction vectors and some other information like magnitude or something?

Or do i have to find the relative velocity vectors separately the same way id find the directions themselves.

2

Did you see my comment? Project the rigidbodies velocity vector onto the .right and .up of the camera and take the magnitude…

4

OK, that makes a little more sense now. And, if I understand you correctly, you want the forward velocity relative to the camera’s “forward horizontal direction”, as if the camera wasn’t tilted down looking at the object?

I believe the following might do something like you need, using what @whydoidoit suggested with Vector3.Project.

Vector3 cameraForwardHorizontalVector = Vector3.Cross(transform.right, Vector3.up).normalized;
		
Vector3 velocityCameraForward = Vector3.Project(velocity, cameraForwardHorizontalVector);
Vector3 velocityCameraBackward = velocityCameraForward * -1;
Vector3 velocityCameraRight = Vector3.Project(velocity, transform.right);
Vector3 velocityCameraLeft = velocityCameraRight * -1;
3

What whydoidoit said