Here I show 3 renders of the same scene.
This one is Q4 default (that's silk):
This one is Q4 with glossy (instead silk):
And this one is Q3 default (that's glossy):
As can be seen, in the Q4 glossy version the annoyng bright dots of Q4/default are gone, but you cannot just switch to Q3 to get glossy, as there is a big difference between Q3 and Q4 glossy renders as you can see.
By the way the second picture suffers from the "black squares" problem, but as long as there are not many of them they can be easily fixed editing the final rendered image.
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If a long walk every day were healthy, mailmen would be immortal.
