www.kraytracing.com

Hi Janusz,
After all this time, I decided to learn Kray seriously because it seems that the future will tell us that this is a very good choice.
Attached a jpg test. Can you explain to me what happens in the red circle?
thank you very much
Franck

The source of this error comes from bad photon map or no Path Passes (in this case zero value) or bad wire.
I suggest turn ON Path Passes in FG Tab minimum 1/50%
Will be nice to see Photon Estimate/Precomputed render to see cells.
Also to check where is problem: photon map or Final Gathering - just Turn ON QMC and check render (by this you will exclude Final Gathering problem necause QMC offers no interpolated sampling). If still it is, then is bad photon map (can be too big GI resolution and no Path Passes )
Path Passes in Final Gathering tab are extra Photons in Path Tracing mode (so same as Maxwell) which make more accurate position in corners. It makes slower render but more accurate samples.
Edit
In extreme problems switch Kray to Path Tracing (must be quite high FG to reduce noise: 1000/1000 and more) Than you will rendr in clean Path Tracing mode (exactly the same as in Octane or Maxwell ...almost the same)
Of course render will be minimum ~ 10 times slower then Final Gathering or 4 times slower then QMC. For Path Tracing you do not need photons.

Very Exciting ! Now, he'll have to understand
Thanks very much

Next time post basic scene with problem, please.