Gizmos.DrawRay

Description

Рисует луч с началом в точке from до точки from + направление direction.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnDrawGizmosSelected() {
        Gizmos.color = Color.red;
        Vector3 direction = transform.TransformDirection(Vector3.forward) * 5;
        Gizmos.DrawRay(transform.position, direction);
    }
}