denoiser needs to break tiles down by zdepth to stop edge artefacts

Love the denoiser in blender, but sometimes the samples need to be really high to stop artefacting around edges of objects.

For example I'm rendering a model around 6 metres from the camera, and behind that there's a field of corn. The denoiser is mixing the colours of the foreground object with those of distant corn, producing blocky artefacting.

This could be avoided if the denoiser seperated each tile into several pieced to be denoised seperately based on zdepth. So basically it should read each pixels zdepth value, and if there's a value jump of more than 1 between pixels then drop the current pixel into a new denoising piece. Once all the pixels have been made into pieces, then denoise.......or better still store the piece information and denoise after rendering (this would be great as then denosing could be done non destructively...allowing the user to try different denoising values without having to re-render).