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Fix smooth follow example in interpolation #6134

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Fix smooth follow example in interpolation #6134

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13 changes: 7 additions & 6 deletions tutorials/math/interpolation.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -118,24 +118,25 @@ Interpolation can be used to smooth movement, rotation, etc. Here is an example

func _physics_process(delta):
var mouse_pos = get_local_mouse_position()

$Sprite2D.position = $Sprite2D.position.lerp(mouse_pos, delta * FOLLOW_SPEED)
Comment on lines -121 to -122
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@Flarkk Flarkk Sep 12, 2024 •
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I suggest keeping the current version, but adding a comment right after :

# An alternative version with even smoother results and a little more math : 
# $Sprite2D.position = $Sprite2D.position.lerp(mouse_pos, 1 - exp(-FOLLOW_SPEED * delta))

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I don't know. Kind of kills the idea of fixing the incorrect method in the first place.

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But the original method is not really wrong in itself. It just produces less smooth results, which might not be a problem in the context of a beginners tutorial.

var weight = 1 - exp(-FOLLOW_SPEED * delta)

$Sprite2D.position = $Sprite2D.position.lerp(mouse_pos, weight)

.. code-tab:: csharp

private const float FollowSpeed = 4.0f;

public override void _PhysicsProcess(float delta)
{
Vector2 mousePos = GetLocalMousePosition();

Sprite2D sprite = GetNode<Sprite2D>("Sprite2D");
Vector2 mousePos = GetLocalMousePosition();
float weight = 1f - Mathf.Exp(-FollowSpeed * delta);

sprite.Position = sprite.Position.Lerp(mousePos, delta * FollowSpeed);
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Same as above

sprite.Position = sprite.Position.Lerp(mousePos, weight);
}

Here is how it looks:

.. image:: img/interpolation_follow.gif

This useful for smoothing camera movement, allies following you (ensuring they stay within a certain range), and many other common game patterns.
This is useful for smoothing camera movement, allies following you (ensuring they stay within a certain range), and many other common game patterns. Notice that making movement framerate-independent is more involved than just multiplying weight by delta value.
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The final notice not only doesn't bring much information, but may add confusion. I'd rather not add it.