Detect Collision From Bottom?

Questions & Answers
1

Hello UA,

For my game, I have an object with a box collider. When the object is grounded, the player can make the object jump. The thing is though that my script is using

function OnCollisionStay ()
{
    grounded = true;    
}

This is good and all but if I collide up against a wall and hold the Jump button, the object rises. What I need to do is for grounded to become true ONLY if there is collision from the bottom of the collider. How would I go about doing this? I could use raycasting but I'm not sure if that's the best choice...

Thanks In Advance :)

2

This question is a bit old, but hopefully this will be helpful to someone.

You can do a raycast, but we use this following method. The only problem with it is if for some reason the initial collision is not below - but you could probably use OnCollisionStay to solve that.

void OnCollisionEnter(Collision collision)
{
    if(collision.contacts.Length > 0)
    {
        ContactPoint contact = collision.contacts[0];
        if(Vector3.Dot(contact.normal, Vector3.up) > 0.5)
        {
            //collision was from below
        }
    }
}