KinematicBody won't move along z-axis (Godot) - godot

Question

I'm beginning a new project and just started coding the movement script. I'm using the same old method I use every time but for some reason I cant move forward and backwards(z-axis). This is odd because left and right (x-axis) uses functionally identical code and works fine. Here's my code:
func _physics_process(delta):
velocity += gravity * delta
_get_input()
velocity = move_and_slide(velocity, Vector3.UP)
func _get_input():
var vy = velocity.y
var dir = Vector3()
velocity = Vector3()
if Input.is_action_pressed("forward"):
dir += -transform.basis.z * speed
if Input.is_action_pressed("back"):
dir += transform.basis.z * speed
if Input.is_action_pressed("left"):
dir += -transform.basis.x * speed
if Input.is_action_pressed("right"):
dir += transform.basis.x * speed
velocity.y = vy
velocity.x = dir.x
velocity.z = dir.z
What is wrong?

Answer 1

Here is an alternative approach based on the following assumptions:
Gravity direction is global.
The KinematicBody can be oriented freely.
The controls follow that orientation.
The speed is global (this would only matter if the physics body is scaled, and you should avoid scaling physic bodies anyway).
We start by building a local direction vector:
var local_direction:Vector3
if Input.is_action_pressed("forward"):
local_direction += Vector3.FORWARD
if Input.is_action_pressed("back"):
local_direction += Vector3.BACK
if Input.is_action_pressed("left"):
local_direction += Vector3.LEFT
if Input.is_action_pressed("right"):
local_direction += Vector3.RIGHT
In fact, we can do that better than that:
var local_direction := Vector3(
Input.get_action_strength("right") - Input.get_action_strength("left"),
0.0,
Input.get_action_strength("back") - Input.get_action_strength("forward")
)
Then we transform it with the global basis:
var direction := global_transform.basis.xform(local_direction).normalize()
Then we can get rid of the y component:
direction.y = 0.0
And scale it, so it is a velocity:
velocity = direction * speed
And, of course, you would set the y component of the velocity we have, because the gravity computation handles care of that:
var v_velocity := velocity.y
velocity = direction * speed
velocity.y = v_velocity
All toghether:
var local_direction := Vector3(
Input.get_action_strength("right") - Input.get_action_strength("left"),
0.0,
Input.get_action_strength("back") - Input.get_action_strength("forward")
)
var direction := global_transform.basis.xform(local_direction)
direction.y = 0.0
var v_velocity := velocity.y
velocity = direction * speed
velocity.y = v_velocity