Iray with Daz 4.20 Fireflys issue

bwise1701

I have been forced back to CPU rendering with my upgrade to 4.20 and I'm seeing a lot more firelfys in an interior seen with several low opacity (0.0001) emission sources to boost light from the windows AND an HDRI skydome - relatively low illumination - would love some pointers to fine tune render params - search but didnt find anything definitive - I do have caustic sampler on and quality set to 5 - any pointers to docs or other threads on this topic would be much appreciated.

Thanks

Hylas

bwise1701 said:

(...) with several low opacity (0.0001) emission sources to boost light from the windows AND an HDRI skydome (...)

 

Ghost lights behave differently now in 4.20.

Basically, you now need to turn down the opacity even more and crank up the lumen even more, if I understood it right.

https://www.daz3d.com/forums/discussion/551301/ghost-lights-what-s-happening-and-what-s-next/p1

KindredArts said:

(...)

You can achieve this by using a cutout opacity of 0.0000001 and a luminanace value of 1000000000.0. I set the luminanace units to cd/cm^2. With this in mind, it won't be a huge upheaval to make older IGL kits work normally again, you'll just have to bare with me while i get them all back through QA.

Another methodology that has arisen because of this iray update, it matte lighting. You've probably seen this in other threads, there's even a super handy script by Jag11 here. I actually really like this method, but a downside of its usage is that you'll still see the light mesh in reflections, and i'm not entirely sure there's a workaround to this. You do get a nice glossy effect though, and they work really well with the new VDBs.

(...)

Richard Haseltine

If the render is dropping to CPU then it may well be timing out before it has reached the convergence target, whhich will potentially leave a lot of noise (not fireflies) even without the loss of light. Is your hardware no longer supported for GPU rendering or is it just a driver issue?