Compute shader not retrieving data to RWStructuredBuffer

Unity Engine
1

Hi,

I have been working with compute shaders for some months on Mac and Unity 2020.
I’m testing the following very simple compute shader on Unity 2021.3.4f1:

#pragma kernel PerlinHeightMapCompute

float4 perlinHeightMapOffset;
uint mapLength;
RWStructuredBuffer<float> heightMap;

[numthreads(32,32,1)]
void PerlinHeightMapCompute (uint3 id : SV_DispatchThreadID)
{
    if(id.x < mapLength && id.y < mapLength)
    { 
        heightMap[id.y * mapLength + id.x] = 1;
    }
}

I set the values for the compute shader with this c· code:

shader.SetInt("mapLength", heightMapSettings.mapSize);
        shader.SetBuffer(kernelHandle, "heightMap", heightMapBuffer);

        shader.SetBuffer(kernelHandle, "CurveKeyframes", keysArrayBuffer);
        shader.SetInt("CubicHermiteSplineFramesCount", keysArrayBuffer.count);

        shader.DispatchIndirect(kernelHandle, computeArgsBuffer);
        AsyncGPUReadback.Request(heightMapBuffer, HeightMapBufferCallback);

And receive the heightMapBuffer with:

heightMapBuffer = new ComputeBuffer(settings.m_heightMapSettings.mapSize * settings.m_heightMapSettings.mapSize, sizeof(float));

void HeightMapBufferCallback(AsyncGPUReadbackRequest readbackRequest)
    {
        if (!readbackRequest.hasError)
        {
            if (readbackRequest.done)
            {              
                Log();
                gpuDataCount++;
                DataReady();
            }
        }
    }

The Log function just logs some data that is consistent except for the values of heightMapBuffer which all are zero:

heightMapSettings.mapSize = 64
computeArgsBuffer = [2,2,1]
This is consistent because of [numthreads(32,32,1)] in the compute shader (2 * 34 = 64)

readbackRequest.width = 16384
Which is the size that I set for heightMapBuffer:

heightMapBuffer = new ComputeBuffer(settings.m_heightMapSettings.mapSize * settings.m_heightMapSettings.mapSize, sizeof(float));

Indeed I have use nearly the same code in other projects.

Any idea why the AsyncGPUReadbackRequest is retrieving me:
[0,0,0,0,0, …0] (like not prossesed or retrieved too early) instead of [1,1,1,1,…1]

Edit:
It’s definitely the AsyncGPUReadbackRequest, because when I replace:

  shader.DispatchIndirect(kernelHandle, computeArgsBuffer);
  AsyncGPUReadback.Request(heightMapBuffer, HeightMapBufferCallback);

by

shader.Dispatch(kernelHandle, 2, 3, 1);
Log();

I get the values [1,1,1,1,…1] for heightMapBuffer.

The Log function is:

float[] heightMap = new float[settings.m_heightMapSettings.mapSize * settings.m_heightMapSettings.mapSize];
heightMapBuffer.GetData(heightMap);
Debug.Log(string.Join(",", heightMap));

Thanks.

2

Same problem