cycles black dots...

do you have any idea why black dots keeps appearing after some 5400 render passes in Cycles?



here you can see that the images is rendered fine, but there some annoying black spots that won’t disappear.
any suggestion, please?

here are the render settings :


note that the lights have more that 100 power (ie the chandeliers have 1111 strenght)

Perhaps the scale has something to do with it?

more precisely, please :slight_smile:

more precisely, please ?

I think ropsta mean the scene is extremly scaled. If 1 Blender Unit is 1 meter may the room is 100 meter long or 1 cm.
Some pathracers have problems with wrong (unreal) scaling .

Cheers, mib.

In other words, take all your objects (including camera and lights), parent them to a new empty at the center of the scene, and scale that empty from 1 to 100 – if everything is attached to the empty, it should all look the same in wireframe view. But the render itself might show different behavior…

it cannot be it, because the room has the correct size: 20m x 10m x 3.44m
it must be something else…

Could you post the blend file? The textures probably don’t matter, as long as the dots still happen. I’d love to have a go at it…

Lol. Sry. The scale of the render’s resolution…

You have an odd numbered resolution so the scale might be affecting the outcome.

Look through your scene and try to find any materials that use a Velvet BSFD closure. They are generally buggy around the place for some reason. Try using a mix closure or a fresnel blend and it will reduce the effect heavily. Although may not actualy make it go away. Simply avoiding the Velvet BSFD worked for me…

@@Wefyb no i don;t jave any velvet
@ropsta: it’s not the render scale
this is what i get after 16620 passes :frowning: those black dots simply doesn;t wanna dissapear :expressionless: this one doesn’t have No Caustics checked


and this one is after 2000 passes, you can see the black dots starting to appear: ( and this one have No Caustics checked)


those black points keep appearing and appearing :((

In windows you use glass? Maybe this glass gives such artifacts …
Instead of windows, use the fake portals.
Example here

firstly i thought black points appear because of the light ( that is the bulbs from the chandeliers) but is it not that. Nor the fact that i use Yes Caustics.

if i use Yes Caustics this is what i get if i render only the chandelier:



noise, yes, because it seems that cycles doesn’t wanna render caustics very well, hence the white dots, but there are no black dots, what so ever, so the pictures above are not broken because of the light.
There must be something in the scene, but what could that be.???

here the render with No Caustics


So the problem is not the light, because i have the same chandeliers in the first pictures on this thread.
Anyone has encountered the black spots problem ?

AlexDS: I don’t want to pressure you or anything, but if you posted a simplified .blend that exhibits the problem, I bet, as a group, we could come up with a solution, or at least pinpoint the issue… We’re all curious to see it in action, and this could also help to determine if it’s a bug, or something else.

That’s because Cycles right now uses an algorithm to evenly distribute all new samples with each pass.

The reason renderers like Luxrender can produce clear caustics in short time periods compared to Cycles is due to the Metropolis sampling algorithm where an area around successful contributions is explored to reduce noise and also create clear caustics in a much shorter time frame.

Currently, the GI part is not really as high a priority for Brecht as is bringing in features in BI used for compositing like render passes.

The black dots though is likely a bug, there’s still a few major bugs yet in the engine (like what you get when mixing glossy and diffuse closures together if they both have a texture input for color)

thanks @Ace_Dragon, so will have to wait patiently then :frowning:

Try your test room again with a highly reflective surface at the bottom and see if it happens again.


done, no black dots with Caustics on!

The unbiased credo

wait patiently then

You are experiencing the state of the technology as it stands. The black dots are bugs or unresolved pieces of code that never terminated correctly.

@Atom, but i hope they are about to be resolved, right ?
it think are some materials or some geometry from my scene that screws everything up. Not sure what that could be…
Are you experiencing something like that dots with some materials that you noticed ?

Aaaand what “The unbiased credo” does mean? :smiley: