How to make a function like this from UE4(RotationFromXVector)

Question

Here it says what it does
https://docs.unrealengine.com/4.27/en-US/BlueprintAPI/Math/Conversions/RotationFromXVector/

Answer 1

You don't need to. Godot uses transform. If you have two nodes A and B and and you want to face A's forward direction to B then just do:

B.transform.basis.z = A.transform.basis.z

Remember In Godot, Z axis is forward, X axis is right and Y axis is up. More info here :
https://docs.godotengine.org/en/stable/tutorials/3d/using_transforms.html#obtaining-information

Comments

for example I want to get the forward of velocity (Vector3) and apply it to the player

as I understand from what you said is that I have to only set the z axis of the player to the value of z axis in the velocity

like

Player.transform.basis.z = velocity.z

---

I'm sorry for late reply but yes, that should work.

---

And yes one more thing; there are also global transforms in Godot. So if by chance its not working maybe you need to swap between global to local or vise versa based on your scenario.