Frustration with graininess and question about "min Sample"

DarkElegance

Right, so last night I finally got the image set up the way I wanted. Set my render settings and left it to do its thing. It ran roughly 18 hours. It was looking good then it...stopped.

Normally the settings I use, renders fairly well. Nothing I cant tweek out in postwork, But this time, It was still quite grainy.
(btw, max samples-25000. Max time-nil, render converged ratio-100%, render quality enabled, size, 2560x1440...my normal settings)
But for some reason this time...it just is not doing its thing.

But I am curious(I have now looked through a few youtube tuts', a few forums, but cant find the answer) The "Min Samples" is set at the standard "5".
I cant find a single article that tells me what happens if I move this up or down?

What happens?

Will it improve the over all look(not caring about time)

This may seem a daft question but I have never messed with it and now, kind of wondering....


(Btw, I have altered the lighting, shutter speed etc)

RL_Media

Did it reach 25000 samples? If not, I would turn off render quality as well. Usually I disable that, that way it's only gonna stop once the samples is reached. If the render still looks bad, I just pump up the min and max samples. For min, I usually pump that up to like 100 to start. Admittadly, I haven't really done any tests to see what the difference is just increasing min alone does. 

felis

What caused your render to stop?

My guess would be time. And how many samples had it done at that time?

If you set it to "0" you disable time as a stop criteria.

A possible cause is that your render was to large to fit in your GPU and then made fallback to CPU which is much slower.

But lots of noise usually means to litlle light, or maybe just an area with too little light.

"Min samples" just mean minimum number of samples, so other stop criterias can't stop it till then, which shouldn't effect your render.

DarkElegance

felis said:

What caused your render to stop?

My guess would be time. And how many samples had it done at that time?

If you set it to "0" you disable time as a stop criteria.

A possible cause is that your render was to large to fit in your GPU and then made fallback to CPU which is much slower.

But lots of noise usually means to litlle light, or maybe just an area with too little light.

"Min samples" just mean minimum number of samples, so other stop criterias can't stop it till then, which shouldn't effect your render.

Normally it runs till it goes "Its done".

It apparently figured the image was done. I decided it was not. But I have adjusted the Things I normally would to allow more light into a dark scene (shutter speed, f/stop, etc). I am using the same settings I used in my last piece. But for some reason this time(actually have more lights in this one) this time, its grainy. Really grainy. Not a little that can be tweeked out in post work.

No error window.
(which normally happens when it hits a snag)
It just seemed to go "yup, its done".

felis

If you look in the log (Help > Troubleshooting > View Log FIle) you can see the reason it stopped.

And changing shutter speed or f-stop does not give more light in the scene. It just changes the tone mapping. You can use tone mapping to give the impression that the room is poorly lit, even though there is plenty of light.

You need to either add new lights or emissive surfaces, or increase the intensity of those already in the scene. I would think adding new light in the area with the noise would be the best solution.

Richard Haseltine

felis said:

If you look in the log (Help > Troubleshooting > View Log FIle) you can see the reason it stopped.

And changing shutter speed or f-stop does not give more light in the scene. It just changes the tone mapping. You can use tone mapping to give the impression that the room is poorly lit, even though there is plenty of light.

You need to either add new lights or emissive surfaces, or increase the intensity of those already in the scene. I would think adding new light in the area with the noise would be the best solution.

While increasing intensity does seem to help a bit (I think as it allows the paths to bounce a few more tiems before returning a value) it won't help much with aras that are receiving little direct light but rely on light paths bouncing in - those will take a long time to lose their noise as theya re hit by paths (sampled) relatively infrequently. Adding more light sources to fill them in a bit, then adjusting the tone mapping to retain the desied look, is the core of a solution.

IceCrMn

Also, if you want to render with only number of samples as your only stop condition then just turn off "Rendering Quality Enable".

Setting "Nominal Luminance" helps out alot also. Around 150 or so should be fine. 0.00 is disabled(unrestricted I believe). Which can lead to fireflies. I think 180 or 190 is the brightness of white paper in direct sunlight. I start out around 100 and go up or down depending on the results I get with the lights I'm using.

DarkElegance

Richard Haseltine said:

felis said:

If you look in the log (Help > Troubleshooting > View Log FIle) you can see the reason it stopped.

And changing shutter speed or f-stop does not give more light in the scene. It just changes the tone mapping. You can use tone mapping to give the impression that the room is poorly lit, even though there is plenty of light.

You need to either add new lights or emissive surfaces, or increase the intensity of those already in the scene. I would think adding new light in the area with the noise would be the best solution.

While increasing intensity does seem to help a bit (I think as it allows the paths to bounce a few more tiems before returning a value) it won't help much with aras that are receiving little direct light but rely on light paths bouncing in - those will take a long time to lose their noise as theya re hit by paths (sampled) relatively infrequently. Adding more light sources to fill them in a bit, then adjusting the tone mapping to retain the desied look, is the core of a solution.

Aye, I had learned to do that from a tutorial on youtube The gentleman was showing how to get rid of noise in shadowed areas. So I had tried the trick on this piece. I am re-rendering it. I have adjusted some of the settings and added a ghost light as well to light the area that is just grainy as heck.

Normally the settings I use give decent results.

Oh and nothing in the troubleshooting log. It just seemed that the settings told Dazstudio "Yup its done".