Ideas for detecting collision speed with trigger?

So basically I have a car flying off a ramp. I want to put a trigger at the top counting the speed of the car. If it is fast enough it will start doing a flip (already scripted the flip :smiley: ). So any ideas on detecting the speed of the car when it gets to the top of the ramp?


Put a BoxColider component on an empty gameobject (without any mesh) at the top of the ramp. Set the Trigger to true on that colider.

Attach a new script to that colider which checks for the car and it’s speed. Something like…

using UnityEngine;
using System.Collections;

public class RampFlipper : MonoBehaviour {
    void OnTriggerEnter(Collider other) {
        if(other.gameObject.tag.Equals("Car")) {
             Car car = other.gameObject.GetComponent<Car>();
             if(car.GetSpeed() >= FLIP_THRESHOLD) {

To get the car’s speed, you can store the previous position of the car on each Update() call and then divide it by the Time.deltaTime. Something like…

private Vector3 previousPosition;
private float speed;

private void Update() {
   float distanceSinceLastFrame = Vector3.Distance(transform.position, previousPosition);
  speed = distanceSinceLastFrame / Time.deltaTime;

public float GetSpeed() {
   return speed;

Hope this helps.

I think I would make a collider, make it a trigger, place it at the top of the ramp, and OnTriggerEnter I would inspect the attachedRigidBody’s velocity magnitude, basically as @Cherno describes.