Check the video for more explain https://youtu.be/aMEu6FcdxFQ

Mono_Graphics_DrawProceduralIndirect.cs

using System.Collections.Generic;
using UnityEngine;

namespace Code
{
    /// <summary>
    /// The simplest example to show how to use  Graphics.DrawProceduralIndirect
    ///
    ///  What it does:
    /// 
    ///  - just draw a triangle on scene
    ///
    ///  How it dose : 
    /// 
    ///  - push Vertex data to a ComputeBuffer and upload to video card memory
    ///  - use a custom shader to read that part data and render a triangle
    /// 
    /// </summary>
    public class Mono_Code : MonoBehaviour
    {
        public Material MT;

        private ComputeBuffer mArgBuffer;

        private Bounds mBounds;

        private ComputeBuffer mVertexBuffer;

        private GraphicsBuffer mIndexBuffer;

        void Start()
        {
            mVertexBuffer = new ComputeBuffer(3, sizeof(float) * 3, ComputeBufferType.Structured, ComputeBufferMode.Immutable);
            mVertexBuffer.SetData(GetVertexData_List());


            mIndexBuffer = new GraphicsBuffer(GraphicsBuffer.Target.Index, 3, sizeof(int));
            mIndexBuffer.SetData(GetIndexData_List());

            MT.SetBuffer("VertexDataArray", mVertexBuffer);

            mBounds = new Bounds(Vector3.zero, new Vector3(100, 100, 100)); //用于快速剔除
            mArgBuffer = new ComputeBuffer(1, sizeof(int) * 5, ComputeBufferType.IndirectArguments);

            // index-0 : 每个实例有多少个顶点
            // index-1 : 有多少个实例
            // index-2 : start vertex location
            // index-3 : start instance location
            mArgBuffer.SetData(new int[] {3, 1, 0, 0, 0});
        }


        private List<Vector3> GetVertexData_List()
        {
            var result = new List<Vector3>();

            result.Add(new Vector3(-1.5f, 0, 0));
            result.Add(new Vector3(1.5f, 0, 0));
            result.Add(new Vector3(0, 0, 1.5f));

            return result;
        }

        private List<int> GetIndexData_List()
        {
            var result = new List<int>();
            result.Add(0);
            result.Add(1);
            result.Add(2);
            return result;
        }


        private void Update() { Graphics.DrawProceduralIndirect(MT, mBounds, MeshTopology.Triangles, mIndexBuffer, mArgBuffer); }

        private void OnDestroy()
        {
            if (mVertexBuffer != null)
            {
                mVertexBuffer.Release();
                mVertexBuffer = null;
            }

            if (mArgBuffer != null)
            {
                mArgBuffer.Release();
                mArgBuffer = null;
            }

            if (mIndexBuffer != null)
            {
                mIndexBuffer.Release();
                mIndexBuffer = null;
            }
        }
    }
}

Can you post the material shader that you used?