Rendering animations with Cycles: I always want the sampling seed randomised. I’ve just read that you can type “#frame” straight into the seed, but I need more randomness. (I may have multiple machines rendering the same frames but I need the noise patterns to be different so I can stack the renders)
Is there a quick way to create a more random value (say, one that takes the time of day into account)? Something like “#frames + #seconds since midnight”?
You can create a scripted expression and return whatever float value you like. To do this, right-click on the field and add a Driver, it should turn purple if you are using the standard theme. This is actually what the #frame option does, it creates a driver that returns the current frame.
I’ve found the simplest solution seems to be to add a driver, as you say, and then put
noise.random() * 10000
in the field. This gives a perpetually changing seed, meaning I can re-render the same file several times and always get different noise.
Top tip: today I learned you can just type or paste an expression straight into the field (once you’ve added a driver), rather than having to open a graph/drivers pane to do it. Super.