RaycastHit.distance

Расстояние от источника луча до точки удара.

В случае луча, расстояние представляет величину вектора от источника луча до точки столкновения.

В случае сканированного объема или сферы, расстояние представляет величину вектора от точки источника до перемещенной точки, в которой объем контактирует с другим коллайдером.

Обратите внимание, что RaycastHit.point представляет точку в пространстве, где происходит столкновение.

using UnityEngine;
using UnityEngine.InputSystem;

public class Example : MonoBehaviour
{
    // Movable, levitating object.

    // This works by measuring the distance to ground with a
    // raycast then applying a force that decreases as the object
    // reaches the desired levitation height.

    // Vary the parameters below to
    // get different control effects. For example, reducing the
    // hover damping will tend to make the object bounce if it
    // passes over an object underneath.

    // Forward movement force.
    float moveForce = 1.0f;

    // Torque for left/right rotation.
    float rotateTorque = 1.0f;

    // Desired hovering height.
    float hoverHeight = 4.0f;

    // The force applied per unit of distance below the desired height.
    float hoverForce = 5.0f;

    // The amount that the lifting force is reduced per unit of upward speed.
    // This damping tends to stop the object from bouncing after passing over
    // something.
    float hoverDamp = 0.5f;

    // Rigidbody component.
    Rigidbody rb;
    
    [Header("Input Actions")]
    public InputActionReference moveAction;

    private void OnEnable()
    {
        moveAction.action.Enable();
    }

    private void OnDisable()
    {
        moveAction.action.Disable();
    }

    void Start()
    {
        rb = GetComponent<Rigidbody>();

        // Fairly high drag makes the object easier to control.
        rb.linearDamping = 0.5f;
        rb.angularDamping = 0.5f;
    }

    void FixedUpdate()
    {
        // Push/turn the object based on arrow key input.
        rb.AddForce(moveAction.action.ReadValue<Vector2>().y * moveForce * transform.forward);
        rb.AddTorque(moveAction.action.ReadValue<Vector2>().x * rotateTorque * Vector3.up);

        RaycastHit hit;
        Ray downRay = new Ray(transform.position, -Vector3.up);

        // Cast a ray straight downwards.
        if (Physics.Raycast(downRay, out hit))
        {
            // The "error" in height is the difference between the desired height
            // and the height measured by the raycast distance.
            float hoverError = hoverHeight - hit.distance;

            // Only apply a lifting force if the object is too low (ie, let
            // gravity pull it downward if it is too high).
            if (hoverError > 0)
            {
                // Subtract the damping from the lifting force and apply it to
                // the rigidbody.
                float upwardSpeed = rb.linearVelocity.y;
                float lift = hoverError * hoverForce - upwardSpeed * hoverDamp;
                rb.AddForce(lift * Vector3.up);
            }
        }
        Debug.DrawRay(transform.position, -Vector3.up * hoverHeight, Color.green);
    }
}

Дополнительные ресурсы: ,Physics.Raycast,, ,Physics.Linecast,, ,Physics.RaycastAll,.