Because of B.Y.O.B.'s suggestion:
But I used the automatic options as provided in the Blender build from April 11th, they are stored in the bunkercache2.blend file I posted above: There is no option to set indirect cache size any more instead there is a quality threshold I set to "final" (5%).
I used 100 million photon count and automatic lookup radius, brute force radius does not matter for the debug view.
This does absolutly not look like my result, see also the gif sequence above.This is the scene with your parameters:
and this with automatic conditions:
It is a lot better.
My result looks like your automatic one, maybe you are using LuxCoreUI ?
KintuX (here), Luxart (here) and I have tried PGI animation and experienced flickering.
All of us have intuitively chosen to animate the same frame in order to exclude other sources for flickering and instead concentrate on what the cache causes.
We assume if (temporal) cache variance could be diminished, using PGI for object (not only camera) animation would become possible.
The question is what parameters need to be tuned to get less cache variance?
My take is that there is a problem with photon distribution of infinite (sky) lights causing high cache variance prohibiting animation without flicker, even with tuned parameters.
This affects mainly scenes rendered with Lux sun+sky system, which is kind of a standard case.
In order to test this I use my bunker scene with the settings unchanged as in screenshot above and disable the sky background, so there is only sun light left: This looks relatively smooth and I think it could be possible with better parameters to minimize the variance to the point animation is free of flickering.
Now I do the opposite, disable the sun and activate sky only instead (also 10x higher gain in tonemapper because sky alone is too dark): Now this shows a very inhomogeneous photon distribution with a high variance from frame to frame.
My conclusion is that sampling of infinite light photons is insufficient and needs to be improved.
- In combination with sunlight bad skylight sampling is the reason for the flickering we have experienced in our experiments
- The visible splotches show up directly in the caustic cache and disturb caustic renders with skylight
- They show up also in glossy reflections and produce ghost reflections on shiny floors in interior renders with sun+sky.
- PGI with directional light sources shows better results with smoother sampling and might be ready for animation with more fine tuning
Some parameters that might help reducing cache variance like cache filtering value and indirect lookup max count are not exposed in Blender.
Maybe they could get different defaults for animations.