How to get RigidBody2D linear acceleration

Question

I'm getting the acceleration of my RigidBody2D this way (it work):

func _process(_delta):
    calc_acceleration()

func calc_accelerations():
    var v0 = linear_velocity
    var r0 = angular_velocity
    var dt = 0.1
    yield(get_tree().create_timer(dt), "timeout") #wait for dt seconds
    var v1 = linear_velocity
    var r1 = angular_velocity

    acc = (v1 - v0)/dt    #dv/dt
    racc = (r1 - r0)/dt   #dTheta/dt

But the yield() induce lots of errors when my RigidBody2D is deleted from the scene. I use queue_free() to delete it.

Is there a clean way of accessing the acceleration ?
I tried putting a Timer child but it didn't worked with small delay

Answer 1

Any reason why you don't simply use the delta-argument provided to _process?

var v0
var r0

func _process(delta):
    if v0 and r0:
        var acc  = (linear_velocity  - v0) / delta
        var racc = (angular_velocity - r0) / delta
    v0 = linear_velocity
    r0 = angular_velocity

Comments

thanks, I didn't thought about using delta

I just had to put it in physicsprocess() and it worked perfectly

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Can someone explain why (linearvelocity - v0) is not 0 ? It should be zero right because v0 is also linearvelocity of the same frame.

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v0 is actually the linear_velocity of the previous frame in this context if I understood correctly

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Yes, it should be the linear velocity of the previous frame as per the acceleration formula goes, but how do we assign v0 the linear velocity of the previous frame, I am scratching my head over this long time

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Let's say linear_velocity increases by 1.0 every frame,

Frame |  v0  | linear_velocity | v0 = linear_velocity
___________________________________________________
0     |  0.0 | 0.0             | 0.0
1     |  0.0 | 1.0             | 1.0
2     |  1.0 | 2.0             | 2.0
3     |  2.0 | 3.0             | 3.0
...

So you calculate acceleration with v0 and linear_velocity then prepare v0 for the next frame