Rectangle Artefacts appearing at 4K render size but not in Interactive / 2K

[swedgedesign]

Hey guys

I'm working on a client project where the client has asked for 4K renders, I ran lower res renders for approval, and for the finals, all I've changed is the resolution and I get this odd pattern forming on the floor. There is a light off to the left of the image, but I can't share the full image due to an NDA. This seems to happen with this one light in the scene, and I'm rendering the object from multiple angles (and have the same issue).

I've shown a snip from the 2K render, and then the 4K for comparison. Would really appreciate any help, as I've got a fair few more renders to complete for this project (I've never found anything like this before)

P.s. Using the latest stable release (not the Corona 7 dailybuilds)

[romullus]

Try to turn off adaptive light solver in render setup>performance tab. If that won't help, go to developement/experimental rollout and change enviro sampler from adaptive to precise, or normaldep compensated.

[swedgedesign]

Hey romullus

Thanks for getting back to me - switching off the adaptive light solver seems to have done the trick! Is there a particular reason this occurs?

Thanks for the help, appreciate it

[romullus]

Glad to hear it helps. Adaptive light solver should work reliably in most cases, but ocasionally there's still some situations where it fails. AFAIK the only thing you can do in this situation, is to turn adaptive solver off.

[swedgedesign]

That's really good to know for future. After switching it off I never encountered any problems with the rest of my project so cheers for the help man!