the photons in tpt as we all know have a life limit, now i know we don't go to extremes with IRL but in theory the further light goes the less energy they carry (gradualy gets dimmer) so my suggestion is like BRAY they gradually loose visability instead of suddenly vanishing. So what do you think?
and like I said I am not forcing IRL in tpt
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please comment on this

I would suggest visual ( like BRAY), although it would also make sense if the particles them selves disapeard randomly:

------------------- - - - - - - - - - - - - - - - - - - - - - - - -
------------------- - - - - - - - - - - - - - - - - - - - - - - - - -
------------------ - - - - - - - - - - - - - - - - - - -< each particle has a random life span
^ so maybee random life properties perhaps?