A far more poignant song by Pink Floyd (ie David Gilmour) about Syd Barrett was on the same album as "Shine On", and gave the album its title: "Wish You Were Here". Gilmour and Barrett had been best friends at art school, and Gilmour had been drafted in to support (and very quickly replace) Barrett when the latter's mental collapse sadly continued throughout 1968-1969.
It has to be added that Barrett's two solo albums from 1969-70 are arguably the best work he ever produced (despite the brilliance of that first Pink Floyd album, which remains unique) - but perhaps because, rather than in spite of, the fact that his mind was about to reach "interstellar overdrive". His utter, unprecedented silence thereafter lies at the root of his legend.
So, so you think you can tell Heaven from Hell,
blue skies from pain.
Can you tell a green field from a cold steel rail?
A smile from a veil?
Do you think you can tell?
And did they get you to trade your heroes for ghosts?
Hot ashes for trees?
Hot air for a cool breeze?
Cold comfort for change?
And did you exchange a walk on part in the war for a lead role in a cage?
How I wish, how I wish you were here.
We're just two lost souls swimming in a fish bowl, year after year,
Running over the same old ground.
What have you found? The same old fears.
Wish you were here.
For anyone wanting to understand what the fuss is all about, just give yourself 90 minutes to listen to
(a) "Piper at the Gates of Dawn" - Pink Floyd, 1967
(

"The Madcap Laughs" - Syd Barrett, 1969
Sorry for sounding so nerdy on this thread - but I'm a bit of a Syd nut!