Gizmos.DrawCube

public static void DrawCube (Vector3 center, Vector3 size);

Description

Рисует куб с центром - center и размером - size.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnDrawGizmosSelected() {
        Gizmos.color = new Color(1, 0, 0, 0.5F);
        Gizmos.DrawCube(transform.position, new Vector3(1, 1, 1));
    }
}