Blender 2.8 with strange problems when use gpu computer … look images
Cpu render is ok .
gpu render problem
Using composite glare effect
Yeah I’ve noticed that too, there are already a bug report about that …
I’m sure it will be solved sooner than later !
I’ve noticed the same effect in a pretty big project yesterday. But I’ve narrowed it down until there was the cause of the problem. It’s way simpler: I can at least say, that when using small area lights below a size of 1 (e.g. meter), and it’s getting darker (the light source is far away from the object) you can clearly see this problem: CPU renders the tiles darker than the CUDA GPU.
To reproduce the problem:
Create a new scene with the cube, remove the default light, create an area light, resize it to lets say 10% (or 1%… the smaller the bigger the effect) and rotate it that it lights the default cube. Don’t forget to set the render engine to Cycles and activate GPU rendering (in Preferences->System include your CPU for CUDA-Rendering). And there it is:
I’m even not sure if the GPU or the CPU is generating the wrong tiles but at least they don’t fit to each other. 
My rendering configuration:
- Most recent version of Blender 2.8 (no Beta)
- AMD Ryzen Threadripper 2950X
- NVidia RTX 2080
- NVidia GTX 1060
- Most recent NVidia (game ready) drivers
Can anyone confirm that this is correct?
What is the status of this bug report (if it’s the same error)? Has anyone the link to it? Maybe this input helps to solve the problem.
So, basically 99.99% of all realistic lights?
I would say yes! Global scene lighting may be another point, but as I wanted to replace small mesh lights (which I use in most of the cases) by area lights because of a LOT less noise, I created area lights with 10x10cm that causes these ugly tiles in my scene especially in darker shadow areas.
can you provide a test file and / or fill a bugreport ?
The initial issue of the post is long time solved, but I guess it’s a new one, probably this as already been reported but if not , just submit a .blend as simple as your test file and I’m sure it will be fixed soon !
Of course I can provide a Blender file. I just wasn’t allowed to post it in my first reply, but here is the file that produced cube image above:
TileProblem.blend.blend (104.7 KB)
I’ve filled a bug report : https://developer.blender.org/T69535 , These kind of bugs generally have a short live on earth…
Oh that would be wonderful for my project! 
Thank you very much for creating the bug report! I will stay tuned on it. 
The bug has been flagged as confirmed and with medium priority in the meantime. But apart from this nothing has happened so far. I can’t render intact images in my current project. Have tried the newest NVidia drivers as well as the nighly build of Blender 2.81. Nothing changed, so it stays a current bug. I guess there’s no possibility to give it a higher priority than it already has, right?
Is is just my personal feeling or do I am one of approximately three people in the world who work with small sized area lights in blender? 
I rendered a video this morning for demonstrating this bug. Next to the different brightness levels of this bug (which could be avoided in diabling either GPU or GPU) please also have a look on the underlying Moiré effect that can’t be avoided at all.
Just curious, what kind of real lights are these? 0.3mm? To me, it would be okay for a diode, but not something that really lights up a scene. I would consider scaling things up, as the first thing that strikes me is accuracy issues.