Fireflies and poor lighting help

[kraken]

Hi,

I'm trying to do a light study and the scene looks aweful. I've bumped the samples up to 5000 and it still looks bad. There's got to be a way to make this work.

Thanks for you help.

James

[justavisitor]

I think you're using Path tracing - try Direct Lighting and Ambient occlusion.

[kraken]

Thanks, I tried all of them PMC, Path Trace, Direct Light, all different settings and hotpixel removal cranked up. The best solution I've found so far is "Cycles".

This was done with 500 samples. Pain in the butt reassigning the materials.

[justavisitor]

Thanks, I tried all of them PMC, Path Trace, Direct Light, all different settings and hotpixel removal cranked up. The best solution I've found so far is "Cycles".

This was done with 500 samples.

Weird, I've never seen fireflies like those in your first render (except with path tracing). But 'artificial' lights are tricky in Octane (compared to the Octane world-light which is awesome).

The Cycles image is nice, I didn't know the engine was that good.

[grimm]

The first thing I would try is to decrease the gloss on your wall texture. That is where most of your fireflies are coming from I would think. How are your lights setup? If the lights are behind glass that can cause issues as well. Try to make the lights as large as you can. Also if you increase the lights importance sampling so the lights will be more prefered. Lastly you can try and increase the caustic blur a little as this will help a bit too.

[justavisitor]

Also if you increase the lights importance sampling so the lights will be more prefered.

How do you do that? The only Importance sampling I'm aware of is a general binary check-box (and it doesn't affect fireflies). Is there a way to give specific lamps more or less than importance than others?

As luck will have it, I just rendered a scene that's exactly as useless as Kraken's and nothing helps. Octane doesn't seem to like lights at certain (sharp) angles.

[grimm]

Do you have a scene you could share, as I'm having a difficult time even building a scene with these issues. Here is where the importance sampling is:

Here is a simple scene I attempted to get a lot of fireflies. I have three very small light sources and the environment has been set to low light.

The interesting thing about this is that I had to set the roughness really low, in this case it's set to 0.01. But when I up it slightly to 0.1 the fireflies go away:

Glossy is set to 1.0 for both, so if you have an example .blend file I would be very interested to try and solve this.

[justavisitor]

Do you have a scene you could share, as I'm having a difficult time even building a scene with these issues. Here is where the importance sampling is:

The attachment sample-rate.jpg is no longer available

Here is a simple scene I attempted to get a lot of fireflies. I have three very small light sources and the environment has been set to low light.

The attachment firefly1.png is no longer available

The interesting thing about this is that I had to set the roughness really low, in this case it's set to 0.01. But when I up it slightly to 0.1 the fireflies go away:

The attachment firefly2.png is no longer available

Glossy is set to 1.0 for both, so if you have an example .blend file I would be very interested to try and solve this.

Hi grimm,
Thank you for testing this out. I don't own these scenes so I can't upload them, but the problem is the exact same as kraken's (maybe he's willing to share his .blend): Hundreds of small bright pixels that don't disappear no matter what I do. Around 5k samples, they begin to turn into a sand-like structure, but that's still not what you want from a glossy surface and much higher samples are not practical for animation.

The problem occurs in strong side-lights with no environment lights at all; and on items that are facing you and supposed to be almost but not completely in silhuette if you use strong backlights and very low fill-lights in front of the shadow areas; or if you have a single strong light directed at glossy surfaces at sharp angles. Instead of the expected tones you get a lot of bright points, like using a clotted airbrush where color is sputtered all over the place instead of producing a thin layer of fine particles.

I've tried all possible variations of roughness, and the Texture Emission's Sampling Rate settings don't change anything here...

EDIT: I attached a (granted, very small) sample from one of the files; this is at more than 5k samples, and the surface is supposed to be black. As you can see, it's completely useless and looks very much like kraken's wall.

EDIT 2: The second image is rendered at 10k samples, and it's supposed to be an absolutely clean and smooth surface.

[justavisitor]

Hm,
I have tried a lot now, and I'd like to see somebody make a simple three-point lighting with strong lights on a target in a black room without fireflies.

[justavisitor]

Hm,
I have tried a lot now, and I'd like to see somebody make a simple three-point lighting with strong lights on a target in a black room without fireflies.

Okay, I tried that now on a couple of charachters and I'm beginning to see the light:

Exposure should be reduced - drastically! Try something like 0.1!

So, kraken, our images were simply overexposed (by a lot, if you, like me, had your exposure sitting at 1.0) - or rather over-developed like a physical 400ASA film developed at 1600ASA! You still need 3-4-5000 samples, but then you're ready for prime time!

So the conclusion is that Octane just loves light, like any other camera...