Gizmos.DrawRay

説明

from から from + direction に向けてレイを描画します

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);
    }
}