call once CommandBuffer.DrawMesh, then the scene has two meshes,Why?

My test code is as follows：

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.Rendering;
5. public class CommandBufferTest2 : MonoBehaviour
6. {
7.     private CommandBuffer commandBuffer;
8.     public Mesh sphereMesh;
9.     public Material standardMaterial;
10.     void Start()
11.     {
12.         commandBuffer = new CommandBuffer();
13.         Camera.main.AddCommandBuffer(CameraEvent.AfterForwardOpaque, commandBuffer);
14.         DrawMesh();
15.     }
16.  
17.     public void DrawMesh()
18.     {
19.         Matrix4x4 matrix4X4 = Matrix4x4.TRS(Vector3.up*2f, Quaternion.identity, Vector3.one * 2f);
20.         commandBuffer.DrawMesh(sphereMesh, matrix4X4, standardMaterial);
21.         Debug.Log(" DrawMesh Done ");
22.     }
23. }
24.  

and got following results：

It confused me, why there are two meshes? And it not 3D.

 

I got the answer， my own material replace the standard material, then fixed it.

But I don't know why.
Does there need any special requirements on shader when we use commandbuffer?