Bug ComputeShader not running or not writing to ComputeBuffer

Hello,
I am testing a simple compute shader I wrote in Unity 2021.1.20f1 (URP) and have encountered an issue. Below is MonoBehaviour and ComputeShader, so I am hoping someone will be able to detect what's wrong.

Code (CSharp):

1.  
2. // MONOBEHAVIOUR
3. using UnityEngine;
4.  
5. public class ComputeShaderTest : MonoBehaviour
6. {
7.     [SerializeField] private ComputeShader computeShader;
8.     [SerializeField] private bool validate = false;
9.  
10.     private ComputeBuffer myBuffer;
11.     private int[] validationArray;
12.  
13.     private void Awake()
14.     {
15.         validationArray = new int[5];
16.         myBuffer = new ComputeBuffer(5, sizeof(int), ComputeBufferType.Structured, ComputeBufferMode.SubUpdates);
17.         var writeBuffer = myBuffer.BeginWrite<int>(0, 5);
18.         for (int i = 0; i < 5; i++)
19.         {
20.             writeBuffer[i] = 0;
21.         }
22.         myBuffer.EndWrite<int>(5);
23.         int kernelIndex = computeShader.FindKernel("Start");
24.         computeShader.SetBuffer(kernelIndex, "MyBuffer", myBuffer);
25.     }
26.  
27.     private void Update()
28.     {
29.         int kernelIndex = computeShader.FindKernel("Start");
30.         computeShader.Dispatch(kernelIndex, 1, 1, 1);
31.         if (validate)
32.         {
33.             myBuffer.GetData(validationArray);
34.             for (int i = 0; i < validationArray.Length; i++)
35.             {
36.                 Debug.Log(validationArray[i]);
37.             }
38.             validate = false;
39.         }
40.     }
41.  
42.     private void OnDestroy()
43.     {
44.         myBuffer.Release();
45.     }
46. }
47.  
48. //COMPUTE SHADER
49. #pragma kernel Start
50.  
51. RWStructuredBuffer<int> MyBuffer;
52.  
53. [numthreads(5,1,1)]
54. void Start (uint3 id : SV_DispatchThreadID)
55. {
56.     MyBuffer[id.x] = 1;
57. }
58.  

ComputeShader does not seem to be dispatched or RWStructuredBuffer is not being written to, because Debug.Log returns 0, which are set at buffer initialization. ComputeShader is running each frame, but no change to data is detected.

Actual Result: Five 0's are logged to console when validate flag is checked in inspector.
Expected Result: Five 1's are logged to console indicating successful write operation from compute shader.

NOTE: ComputeShader/MonoBehaviour does not have any compilation errors, as well as no runtime exceptions.
NOTE: I am aware of thread count being low, and not efficient on GPU, but optimization is not the issue I am trying to solve.

Thank you.

 

@aleksandrk it doesn't work neither on 2021.3.19 nor on 2022.2.8, report IN-33394

either ComputeBufferMode.Dynamic and ComputeBufferMode.SubUpdates are not writeable via shader or they return invalid data via buffer.GetData()

on 2021.3 Dynamic returns incorrect data right after buffer.SetData(data); buffer.GetData(data);

 

ComputeBufferMode.Immutable works but you are right, Dynamic and SubUpdates seem to be broken (you can see the dispatch call in RenderDoc but the RWBuffer isn't bound).

Strangely enough, ComputeBufferMode.Immutable does not mean that the buffer is immutable on the GPU. It's only immutable on the CPU after the initial upload.

 

GraphicsBuffer with GraphicsBuffer.UsageFlags.LockBufferForWrite are not bound as RWBuffer as well.
In fact, all these buffer variations are not viable for any cases other than the default ones.