I'm not bug reporting this or anything, I broke it but, check these out...
Whilst playing with some negative light propagation levels and high fake internal scattering I made this happen to the GI pre-pass.
The first one, I've had happen on a few occaisions, usually with high luminosity/reflections etc. never with cloud settings alone! This one actually rendered(ugly, though).
The second, I've never seen before. Anyone else?
Anyhow, it didn't render, prepass finished and render was black.
This second one is weird, eh? A square pass.
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And...
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