The reason for your problem is that the velocity of a colliding body is post-contact. This means that “straight collisions”, where the physics body is at a near stand-still, produce velocities that are small. On the contrary, oblique collisions barely affect the velocity of a moving physics body so the velocity maintains most of its length.
If you wish to bounce your vehicle based on the entry velocity, not the post-contact velocity, you have to store a velocity history.
var previous_velocity = Vector3.ZERO
func _physics_process(delta):
# =================
# === Your code ===
# =================
# [End of function]
previous_velocity = velocity
It’s not bounce() returning a high value – it’s you multiplying the value by 25. Besides, bounce() doesn’t manipulate the length of the vector, it just computes its reflection vector for a given plane normal. Just don’t multiply by 25. You will find that using the previous_velocity, as outlined above, will yield better results.
In cases of inaccurate bounce directions
Depending on your turning speed and delta time of your physics, you may start to notice that previous_velocity does not correctly represent the body’s direction one tick later. That is, of course, because it’s an “old” value.
You can fix this by extrapolating the previous_velocity vector towards the current state of your body. An example of such extrapolation can be found here.
I hope that helps. Let me know if you have additional questions.