Strange artifacts in render

[mmhnemo]

Hi,

 

during my testrenders i stumbled over some weird artifacts in the render which i cant explain.

 

It looks like alot of circles being reflected but there is no such geometry in the scene. It's a closed room with only one (square)area light and GI.

 

GI settings were quite basic with 300 stoch samples but i ruled that out by testing up to 1000 samples with no change at all in the artifacts.

 

Im using 9.5 Studio. Has anyone encountered something like this?

 

Thanks

 

Nicholas

[skala67]

it probably is because your min and max samples are both too low....dont go overboard, but start with testing those levels.

[AJLynn]

I've never seen this in C4D but I've seen it in mental ray - not enough caustic photons. There are reflect caustics off the water, right?

[STRAT]

absolutely. your max samps are way too low. this is quite normal. you've obviously modelled those grout lines in the tiles and not mapped them. this is why.

 

please post up your gi settings

 

i'd suggest to up those max settings considerably. if not, you can always put a render tag on the tiles object and up it's gi accuracy to 95% or something whilst globally keeping the same sample value

[mmhnemo]

Hey guys,

 

thanks alot for the answers.

At first i thought it couldn't be the min/max settings as i used tested amounts but it seems you were completely right. As im approaching settings of like 100/400 and higher the circles start to dissolve. Of course that also means unbearable render times with my old machine.

I will light the scene with direct lighting now.

 

I am wondering though - in most other scenes i could get away with far lower GI settings and not get any artifacts. Also the artifacts seem to be only visible in the reflections on the wall tiles. So it has either to do with the increased amount of geometry in that region( but its only around 10000 polys) or might it have to do with the reflections? Do GI reflections cause problems like this?

 

Im just guessing but maybe someone of you could explain this behaviour.

 

Thanks again

 

Nicholas

[STRAT]

the reason is all the grout lines in the geometry.

 

min samples are for distributing nicely over a flat plain. you dont generally notice artifacts like this with a lack of mins.

 

max samples are for where you have geometry edges. and of course, tiles have loads, and all close together too. a collection of circles like what you had is a typical sign your max samples are too low for that particular area of mesh.

 

as i mentioned above, the usual method to render them out is to up the max samples only. stoch and mins wont effect this. saying that, if you upped the min samples higher than the max's then you have only one over riding sample box to play with, altho render times are seriously compromised.

 

i'd personally stick a render tag to the tiles upping the gi accuracy. this too will help get rid of those artifacts.

 

reflections wont effect gi artifacts either, neither will poly count. your tiles are literally the wrong shape and size for artifact free rendering.

[mmhnemo]

Thanks again Strat - you're a real asset

 

The thing that is rather frustrating about the min/max settings is that you can up the max setting higher and higher and you get lots of samples in the room corners and other prominent geometry but you get almost no samples to hit the tiles area... I guess i'd need a max setting of around 2000 to get sufficient resolution in the tiles.

 

I'll try your tip about upping the accuracy only for tiles tonite and see how this fares.

 

Thank you!