Fireflies and poor lighting help

[justavisitor]

Another weird thing: Hot pix.removal should be set at zero.

[justavisitor]

Another weird thing: Hot pix.removal should be set at zero.

Hot pix. removal at 1.0 (default) and 0:

However, there's a price to pay in perceived sharpness when you reduce Hot pix removal.

But for animations, for instance, it can be set at zero for frames with many fireflies and increased slightly when details are more important.

[grimm]

Hmm still having troubles creating this effect. I'm starting to think that it's the textures used instead of the geometry. I doubled the number of lights and increased their power to 1000. I also moved them so that they are very close to the surfaces. The floor surface I'm using a painted brick texture with displacement. On the wall I just have a simple white glossy texture with spec set to 1. If I disconnect the displacement I start to see the fireflies.

But if I add the displacement back in they mostly go away and the flat glossy wall doesn't appear to get very many of them, which is strange?

Can you share the texture with me? Here is the blend I'm using, although I can't share the brick texture as it's commercial.

firefly.blend

(600.95 KiB) Downloaded 334 times

Oops, forgot to add that both images were rendered to 500 s/px.

Jason

[justavisitor]

Hmm still having troubles creating this effect. I'm starting to think that it's the textures used instead of the geometry. I doubled the number of lights and increased their power to 1000. I also moved them so that they are very close to the surfaces. The floor surface I'm using a painted brick texture with displacement. On the wall I just have a simple white glossy texture with spec set to 1. If I disconnect the displacement I start to see the fireflies.

But if I add the displacement back in they mostly go away and the flat glossy wall doesn't appear to get very many of them, which is strange?

Can you share the texture with me?

I don't have textures in these projects - but what you're saying (and showing) regarding displacement is definitely interesting, I'll look into that.

About reproducing fireflies; I think the 'easiest' way is to have an object, like a person, in a dark room and then point two or three lights at it like in a photo studio - one strong light from the back, a strong light from the side, and, optionally, a less strong fill-light or just a reflective surface from the opposite side. The fireflies get much more visible if you use colored lights.

But perhaps displacement is the cure.

EDIT: Regarding reproducing fireflies: I'm beginning to think that the complexity of the scene might matter: I tried setting lights on characters in two scenes yesterday: Setup A only has two persons in it, three lights and no environment. Fireflies disappear quickly as I turn down Exposure and increase number of samples to 4-5k. But in Setup B, I have the same characters in a setting with multiple 'centers', each of which with its own lighting, and in that scene I need 10k samples to get a decent image. This could seem to be consistent with kraken's first image in this thread; he's got a large, complex scene with several light sources, and his fireflies are really extreme (I didn't even know what he was talking about at first, I thought the fireflies were some kind of cement structure on the wall).

EDIT 2: All of this makes me think about the extremely different ways Octane treats Environmental lights and 'artificial' lights: When you just use World lights, you can instantly see what everything's going to look like in your scene, all objects are pre-rendered correctly in almost real-time, in like 100 samples. But throw in Emissions, and you can no longer freely move around in a pre-rendered scene - instead you move around in total darkness, and characters only become visible when you stop moving around and wait for a couple of hundreds (or thousands) samples to render. Why does it have to be like that?

[justavisitor]

...still puzzled by this:

Here's a detail of a round object in the middle of a complex scene with a variety of lights. The smooth transitions in the top half of the image can be reached at around 500 samples.

But then I pointed a bright, warm spot light close to the object from below. As you can see, the transition from the bottom half to the smooth top half is actually not a transition at all: Pixels are either yellow/orange or black. And this is rendered at 10k samples:

LightBelow1.JPG (8.22 KiB) Viewed 8472 times

So here's my new conclusion:

When lights are too close to the subject, they cease to be lights and turn into grainy dust instead. Like I mentioned in an earlier post, hot pixel removal set to zero helps - though it softens the image - and reduction of exposure does hide the grainy, 'dusty' structure.

But you can't set lights the way you do in a real studio.

[justavisitor]

I just made a fast experiment, replacing a couple of Octane's lights with Cycles', and the result is mindblowing!

You can use Cycles light exactly like real studio lights! At 246 samples, it beats Octane's lights by an unbelivable margin.

Downside: It's significantly slower. And there's something about the overall quality I just don't like; that may be because I don't know anything about Cycles; I just used the first Emission node I could find. Perhaps its lamps are better.

EDIT: Okay, this super weird: I just tried a real Cycles lamp, but it's got the exact same problems as Octane's Emission lights. But again, Cycles' emission lights are incredible; I tried them again and they behave exactly as expected.

This is not to criticize Octane, its environment/world delivers the most gorgeous renders I've ever seen, and I really, really love it! But for artificial lights, there's just no comparison.

[grimm]

Hi justavisitor,

Looking at your images, I don't think you are having a problem with fireflies, but just noise. Fireflies are usually 100% saturated white pixels. It's probably why you needed to set the hot pixel setting to 0 and as you have seen, when it's set to that it starts to blur the image. Which would start to remove some of the noise. I did another experiment with small lights that were recessed into fixtures. The first image I rendered to 500 s/px with the pathtracing kernel.

I'm not sure that what we are seeing here is hot pixels or just heavy noise. In this scene every surface is glossy except the floor which is diffuse. I then switched to the PMC kernel which is much better than PT for this kind of lighting and again went to 500 s/px.

The noise now is significantly reduced.

So what kernel are you rendering with? Are you using blackbody or texture emission? Are your lights a single plane or do they have a structure?

Here is my example scene, where I use a simple ico sphere and texture emission for the lights. The textures on the other surfaces are just the standard glossy or diffuse textures.

firefly1.blend

(584.21 KiB) Downloaded 318 times

One thought I had was that you could render your scene with more light and then darken it in post. This is what movie directors do all the time if they want to control the noise in a scene.

[justavisitor]

Hi Grimm,
You're right, I don't think I can tell the difference between fireflies and noise. But whatever it is, I can't get rid of it, not in spotlight situations. It just looks like kraken's wall.

As for post - well, I think the beauty in Octane is you don't have to fake it. I mean, usually you wouldn' t even get the idea, the images are stunning. And then there's this... I'm really baffled.

I use direct light and ambient occlusion on everything. I've tried everything else and wish I could use path tracing, at least for reflections, but it takes forever to clean up, and I'm making animations so I'm cutting corners wherever I can.

As for lights: I've tried all combinations, and I don't think there's any real difference. Flat planes are obviously easier to aim at a target than round objects, but it's all about distance to the subject.

One thing I haven't tried though, are some kind of filters . Hm. That would obviously make the lights less directional, but then the light source could be pulled further back in a cylinder to emulate a more focused spotlight.

What I really, really don't get, and what literally keeps me awake at night, is why Octane's own world light is so much better. Imagine if you could have that in small lamps somehow!

[grimm]

Grimm,
You're right, I don't think I can tell the difference between fireflies and noise. But whatever it is, I can't get rid of it, not in spotlight situations. It just looks like kraken's wall.

As for post - well, I think the beauty in Octane is you don't have to fake it. I mean, usually you wouldn' t even get the idea, the images are stunning. And then there's this... I'm really baffled.

I don't know if I would say that is "faking it" as you have to do the same thing in the real world, but I understand where you are coming from.

I use direct light and ambient occlusion on everything. I've tried everything else and wish I could use path tracing, at least for reflections, but it takes forever to clean up, and I'm making animations so I'm cutting corners wherever I can.

As for lights: I've tried all combinations, and I don't think there's any real difference. Flat planes are obviously easier to aim at a target than round objects, but it's all about distance to the subject.

One thing I haven't tried though, are some kind of filters . Hm. That would obviously make the lights less directional, but then the light source could be pulled further back in a cylinder to emulate a more focused spotlight.

I don't know as much about DL than I do about the other kernels unfortunately. Have you tried tuning on alpha shadows? Sometimes it helps. The Octane devs are working on a de-noising solution which would help a lot.

What I really, really don't get, and what literally keeps me awake at night, is why Octane's own world light is so much better. Imagine if you could have that in small lamps somehow!

Well the world light is pumping massive amounts of light into the scene. It's not just the sun, it's the entire sky dome that is contributing. With a target like that, almost every surface has a clear view of the light source, so the noise clears very quickly.

Jason

[grimm]

Just had a couple of other ideas, have you tried to put portals on the spot light opening? Personally I haven't really had much luck with portals, but maybe it would help?

I did this animation with a spot light in an absolutely dark room, although unlike your scene this one is very simple, so your observation about geometry probably has some merit.

https://vimeo.com/110720662

Even so you would think that this scene should be the worst case as far as lighting goes, but the noise is not so bad? I think I rendered this to 1000 s/px and with the PT kernel, but I can't remember exactly. Probably the key to this scene is that the spot light is relatively large?

Jason