RigidbodyConstraints.FreezePositionY

Description

Freeze motion along the Y-axis.

//This example shows how RigidbodyConstraints is used to freeze the position and rotation of a Rigidbody in the y axis at start-up.
//It also shows what happens when these constraints are removed, when you press the space key
//Attach this to a GameObject with a Rigidbody to see it in action

using UnityEngine;

public class Example : MonoBehaviour
{
    Rigidbody m_Rigidbody;
    Vector3 m_YAxis;

    void Start()
    {
        m_Rigidbody = GetComponent<Rigidbody>();
        //This locks the RigidBody so that it does not move or rotate in the y axis (can be seen in Inspector).
        m_Rigidbody.constraints = RigidbodyConstraints.FreezePositionY | RigidbodyConstraints.FreezeRotationY;
        //Set up vector for moving the Rigidbody in the y axis
        m_YAxis = new Vector3(0, 5, 0);
    }

    void Update()
    {
        //Press space to remove the constraints on the RigidBody
        if (Input.GetKeyDown(KeyCode.Space))
        {
            //Remove all constraints
            m_Rigidbody.constraints = RigidbodyConstraints.None;
        }

        //Press the up arrow key to move positively in the y axis if the constraints are removed
        if (Input.GetKeyDown(KeyCode.UpArrow))
        {
            //If the constraints are removed, the Rigidbody moves along the y axis
            //If the constraints are there, no movement occurs
            m_Rigidbody.velocity = m_YAxis;
        }

        //Press the down arrow key to move negatively in the y axis if the constraints are removed
        if (Input.GetKeyDown(KeyCode.DownArrow))
        {
            m_Rigidbody.velocity = -m_YAxis;
        }
    }
}