Vertical velocity incorrectly reset moving down slopes while grounded.

Help Physics
1

Godot Version

Godot 4.4.1

Question

I have a particular issue when trying to work on 2D slope physics, which seems to be a huge limitation when attempting to interact with more complicated movement physics. I would like to know if this behavior has a specific workaround.

The issue is that when setting downwards floor velocities on slopes (example here is using 45 degree slopes), move_and_slide will always completely negate the velocity.y component and reset that to 0. What happens is an incorrect velocity length, about only 0.707 of the original set velocity.

Here is a dummy script that exemplifies this issue. In theory the SPEED of the character should be 800 always when moving up and down slopes, but it is actually outputting ~565 on downward slopes, due to velocity being reset to Vector2(800, 0) every frame, then adjusting the velocity angle.

Here is the actual source code I am working with:

Setting floor_stop_on_slope and floor_constant_speed as below and floor_snap_length to 0 will occasionally fix this issue, but it isn’t consistent when it decides to work or not… meaning it’s not a viable solution.

extends CharacterBody2D


const SPEED = 800.0
const JUMP_VELOCITY = -1000.0


func _init():
	self.floor_stop_on_slope = false
	self.floor_constant_speed = true
	self.floor_snap_length = 50
	self.set_floor_stop_on_slope_enabled(false)


func _physics_process(delta: float) -> void:
	# Add the gravity.
	if not is_on_floor():
		velocity += get_gravity() * delta

	# Handle jump.
	if Input.is_action_just_pressed("ui_accept") and is_on_floor():
		velocity.y = JUMP_VELOCITY

	# Get the input direction and handle the movement/deceleration.
	var direction := Input.get_axis("ui_left", "ui_right")
	print(velocity.length())  # this is incorrectly 565 when moving down slopes
	if direction:
		if self.is_on_floor():
			velocity = direction * SPEED * self.get_floor_normal().orthogonal().normalized() * -1
		else:
			velocity.x = direction * SPEED
	else:
		if self.is_on_floor():
			velocity = Vector2(0, 0)
		else:
			velocity.x = 0
	
	move_and_slide()
2

I understand what your issue is but how does that affect how your character moves versus how it’s supposed to?

Can’t test ur game cuz im on my phone rn

3

In the case of the dummy script - it simply doesn’t move at the velocity i want it set to. It makes moving downwards clunkier because it’s slower than moving upwards or on flat ground.

For how I actually want it implemented - it completely kills any form of logic requiring acceleration. I want interesting ground slope interaction for sliding, running, and transferring falling momentum directly into slope sliding momentum. That simply isn’t possible at all with how the engine handles it currently.

4

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image239×340 15 KB

Play with these settings on your CharacterBody2D. For example, it sounds like you want to turn stop_on_slope = false You also might consider changing the max_angle to a greater or lesser angle to see if that gives the feel you want.