How to stop a 3D object(say a car) falling downwards when collided with another 3d object(say a road). I have tried this the whole day but no results.
Unity Physics will control this for you. All you need to do is make sure that a rigidbody component and collider component are present on the car. Make sure that the collider is not set to trigger. Then also add a collider to the road gameObject, making sure that it is not a trigger.
It’s always good practice to Proof of Concept things you’re not too sure about.
Create a new 3D object of plane and add a collider to it, if one does not aready exist.
Then create a 3D object of cube and place it above the plane. Add a collider component to it and a rigidbody component.
Press play and watch the cube fall onto the road.
If you want it to simply freeze on the spot try destroying the Rigidbody.
Destroy(youGameObject.GetComponent<Rigidbody>());