4.x

RigidBody2D: Look at Target

Problem

You want a rigid body to rotate smoothly to look at a target.

Solution

Using RigidBody2D can be tricky. Because it’s controlled by Godot’s physics engine, you need to apply forces rather than moving it directly. Before doing anything with rigid bodies, I highly recommend looking at the RigidBody2D API doc.

To rotate a body, we need to apply a rotational force - a torque. Once the body is rotating, we want the torque to get smaller as we get closer to the final rotation.

This is the perfect situation to use the dot product. Its sign will tell us whether the target is to the left/right, and its magnitude will tell us how far away from the target direction we’re pointing.

Tip

See Vectors: Using Dot and Cross Product for a brief review of the dot product.

extends RigidBody2D

var angular_force = 50000
var target = position + Vector2.RIGHT

func _physics_process(delta):
    var dir = transform.y.dot(position.direction_to(target))
    constant_torque = dir * angular_force

You may be wondering why we’re using the transform.y here, when transform.x is the body’s forward vector. Using transform.x, the dot product would be at its maximum when the body is directly pointing at the target, but we want the torque to be zero at that point. Using transform.y means that our torque will be higher when we’re not aligned with the target.

Skip the Rigid Body Entirely

You can avoid all of this entirely by not rotating your rigid body at all! Instead, change the child sprite’s rotation to point at the target. You can use lerp() or a Tween to make the rotation as smooth as you wish.

In many cases, this will be a great solution. Remember, the underlying body’s orientation doesn’t have to match the attached sprite!