AsyncGPUReadback Class

RenderToCPU.cs

using Unity.Collections;
using UnityEngine;
using UnityEngine.Rendering;

[System.Serializable]
public class RenderToCPU
{
  public event System.Action ErrorOccurred;

  public int Width => _renderTarget.width;
  public int Height => _renderTarget.height;

  private RenderTexture _renderTarget;
  private AsyncGPUReadbackRequest _requestedFrame;
  private bool _isFrameRequested = false;
  private float[] _colorBuffer;

  public RenderToCPU(RenderTexture targetTexture)
  {
    _renderTarget = targetTexture;
    _colorBuffer = new float[_renderTarget.width * _renderTarget.height];
    System.Array.Clear(_colorBuffer, 0, _colorBuffer.Length);
  }

  public float GetColorClamped(int x, int y)
  {
    x = Mathf.Clamp(x, 0, Width - 1);
    y = Mathf.Clamp(y, 0, Height - 1);
    float color = GetColor(x, y);
    return color;
  }

  public float GetColor(int x, int y)
  {
    return _colorBuffer[x + y * _renderTarget.width];
  }

  public void Update()
  {
    // If we have a request frame, check the status
    if (_isFrameRequested)
    {
      if (_requestedFrame.hasError)
      {
        _isFrameRequested = false;
        ErrorOccurred?.Invoke();
        Debug.LogWarning("Failed to read gpu texture");
      }
      // If the frame is done, we can grab the pixel data
      else if (_requestedFrame.done)
      {
        _isFrameRequested = false;
        NativeArray<float> colors = _requestedFrame.GetData<float>();
        colors.CopyTo(_colorBuffer);
      }
    }
    // If we haven't request a frame yet, do so
    else
    {
      _isFrameRequested = true;
      _requestedFrame = AsyncGPUReadback.Request(_renderTarget);
    }
  }
}