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what’s the source of that picture? who made it? with what tools was it made?
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what causes the noise in Blender?
none of us have much interest in fixing stuff if the issue can be prevented.
that’s why ALL the “answerers” on Q&A sites dig and make you reveal details that you think are none of our business. these things become our business because you asked. you may not like it, but it’s for your own good. think of it like a dentist’s appointment. I hate them too.
the way you’re rendering that is the issue, and the way you could render it is the solution. that is fundamentally a computer graphics issue. yes, I’m asking how you rendered it. there are ways to render volumes that don’t cause such artefacts.
if you have had discussions about this elsewhere already, including the Blender forum, please link to them.