Noise/Rendering problem.

[Nox]

Greetings,

I've been using Octane for over 6 months now and this is a reoccurring problem for me. I used to try and work around it and hope it will not happen, but I've build two scenes in the last two days and it happened to the both of them.
Some scenes are just filled with noise no matter what I do and I know they will be the moment the viewport opens.

Here is a 1 sample render that's good:

As you can see, the floor, and other things illuminated by environment lighting are already visible, take note this is a 1 sample render. Once it gets to 100 or so, the image will be mostly visible and it will then just spend the rest of the time getting rid of the noise.

Now here is a bad one:

It starts out almost completely black and, as you can see, it's just an orgy of pixels which, left to continue, will just fill out the image eventually but never go away. Nothing in the room is already illuminated and it's basically treating the environment lighting as if it ware a black body in a dark room. Messy.

Both scenes use the same render settings:

Here is a 16000 samples render that shows the noise never goes away. It's a simple room, bed and the guy. Only daylight, same settings as above.

Ware I to take this model and place him on the bed in the first image, he would look like this at 500 samples, not 16000.

I have tried changing environment lighting, doesn't help.
I have tried setting blur to 1, doesn't help.
I have tried removing all lights but environment lighting, doesn't help.
I have tried adding another light/s to the scene, doesn't help.
Hotpixel removal, doesn't help.
PT, doesn't help.
Portals, don't help.

Any help, even just guesswork, you would be willing to share would be appreciated.

I tried searching for this problem but writing "noise" in the search yields 400 pages of results considering "noise" means six different things here...

[face_off]

Does adjusting the Path Termination Power or GI Clamp as recommended in the Octane Notes link in my signature help?

Paul

[Nox]

Does adjusting the Path Termination Power or GI Clamp as recommended in the Octane Notes link in my signature help?

Paul

The settings I don't have because I didn't update in 6 months?
I assumed a program that requires a constant internet connection will auto-update. My mistake. Although, in hindsight, looks like that was a better decision as a previously 9 hour render now takes 12 hours with the new version.

Setting hotpixel to 0, PTP to 0,1 and Caustic blur to 1 does actually help but that only removes any leftover pixels but the...they're not really pixels, as you can see from that last render, they're more like blotches and blemishes, as if there was another light source that's being rendered poorly...those things are still there and I can still tell they will be there the moment the render starts.

I don't know what GI clamp does but setting it to 1 makes the lighting dim, a lot, and makes it look very bland, especially in places not touched by any direct light. Oh, I guess GI stands for Global Illumination than? If that is the case, setting it 1 would grossly lower the effect of all lighting? That is a trade I am not willing to make.

I just wish to understand why this happens in the first place. I thought it was just bounce and how dark the wall materials are but the first render has considerably darker walls than the second one. More lighting, granted, but that doesn't seem to make any difference.
I don't understand why a render that has over 300 mashes, 32 light sources + Daylight, 3 models, uses 6GB of memory and has enough glass and metal in it that a "cool modern interior designer" would get an erection at the sight of it renders faster and better than a single room with one model, 3 windows and daylight?

[face_off]

I think you need to reduce the Path Termination Power - if you scene is too dark, the rays will get terminated in the dark areas. Reduce this from 0.3 to 0.1.

Paul

[Nox]

I did. I said so in the second line of my previous post. It did help with the noise but noise is not the problem, look behind the noise. Or, better yet, start a render and set Hotpixel removal to 0 right away, wait until it hits 200-500 samples and you'll see the blotches I still have at 14000 samples. Those things are eventually supposed to go away. Sometimes, they don't and that is my problem.

I just want to know how to avoid this problem, what exactly causes it?

Also, when you say the scene is too dark, do you mean there's no direct light hitting it or the light is not strong enough? Because I can set environment lighting power to 500 and they will still be there.

P.S. Appreciate the link in your signature, it is most helpful, thank you for taking the time to do that. I'm sure I'll continue to find it useful in the future as well.

[face_off]

Hi Nox

Without being able to use your scene myself, it's a bit hard to comment on some of your questions. However...there is "dark" noise, where dark areas of the render are not cleaning up (which reducing Path Termination Power fixes) and "light" noise, where there are bright (hot) pixels, which caustic_blur, hot_pixel fix and GI Clamp fix. But I don't understand which you are getting.

look behind the noise

?

Start a render and set Hotpixel removal to 0 right away, wait until it hits 200-500 samples and you'll see the blotches I still have at 14000 samples. Those things are eventually supposed to go away. Sometimes, they don't and that is my problem.

This sounds like "light" noise. So reduce GI Clamp to a level where this goes away, but does not significantly impact the scene lighting.

Also, when you say the scene is too dark, do you mean there's no direct light hitting it or the light is not strong enough? Because I can set environment lighting power to 500 and they will still be there.

If there are dark areas in the scene, they might not be getting any light regardless of the environment lighting power setting.

Paul

[Erick]

Was there something right in front of the camera? Like a Glass front/Window or something?

When I was playing around with trying to make these "god rays" (volumetric rays) visible in a render, through fog or dust, I put a sphere around the camera and played around with the scatter node. Sometimes, if things weren't right, the results were similar a bit.

btw ... wasn't there something confusing with "Hotpixel Removal" as it works the other way around, as one might think at 1st? Meaning that set to "1" there's no removal at all, while set to "0" it's at full force. ... it always got me confused.

[Nox]

No, nothing in front of the camera. It just looks like some materials have adverse reactions to lighting and the problem is it's not the ones you'd think. I always assumed it was high reflection materials (glass, metal, mirrors etc.) that will make a render crawl but that does not seem to be the case, on the contrary, adding more reflective surfaces seems to help it. I suppose it enables light to reach places it otherwise wouldn't. No, the problem seems to come from materials that are matte but have a noticeable bump map or have a specular map but aren't hit by direct light. Skin, for example, falling under both of those categories.

Another thing is large white things, be it ceilings, floors, sheets, sky...a boat. I am unsure of what happens but white seems to scatter light in a very odd manner that tanks the render, at least in my experience, so making things different shades than white seems preferable.

As for Hotpixel, I think the _removal bit may have been added later. It may have been just Hotpixel originally so 0 would be "Hotpixel off". They may have then added _removal to make it more clear...thus making it more complicated. I hope Otoy wasn't purchased by Google at some point.

btw. not to go off topic and all but...were you actually able to make god rays, Erick? I have a soft spot for those and have been just adding them to the scene during postwork. Photoshop saves. But, it would be interesting to see how it would look "properly", although, I suspect the amount of particles required to break light in a straight beam would probably make the render a bit long...like 3 to 7 weeks for me, possibly.

[face_off]

Nox, pls see http://render.otoy.com/forum/viewtopic. ... 7&start=20 for a god rays sample in Poser.

Paul

[Nox]

A small update in case somebody else experiences this problem.

It was displacement maps that caused the blotches on the skin. Looks like even though you may have the "Convert Displacement Maps" off in the setup, Octane will still sometimes load them up for some reason.
So do check those out if you experience problems like these.