Dark Renders

AbnerK

Hi, 

Sometimes when I do a dark, moody scene it renders fast and clean, while other times it's a serious noisy mess. I've never really understood why sometimes I can and sometimes I can't make a clean, dark render. What trick do I sometimes happen on while other times it's missing. Also, and this is the weird bit, sometimes you get a render with nice clean bits then on the same figure a dividing line of serious noise almost as if they light you had used caused it. 

Any tips and tricks for clean, dark renders anyone?

kenshaw011267

There are two choices for reliable quality dark renders (assuming iRay).

1) Let the render run for a long time. How long can vary but things like your tone mapping settings and just how much light is in the scene can have dramatic effects on the time it takes to get the scene to render to an acceptable degree.

2) Actually use more light and then adjust in post work.

Richard Haseltine

2) can also be done, at least in part, with the Tone Mapping options in Render Settings' Editor tab.

AbnerK

kenshaw011267 said:

There are two choices for reliable quality dark renders (assuming iRay).

1) Let the render run for a long time. How long can vary but things like your tone mapping settings and just how much light is in the scene can have dramatic effects on the time it takes to get the scene to render to an acceptable degree.

2) Actually use more light and then adjust in post work.

Thanks, yeah, my computer is not the fastest and I use CPU so letting it render longer really isn't an option. 

'2' has occured to me but it doesn't answer my question of why I get good, dark renders sometimes and others not. I've recently doen a series of renders using two figures and similar backgrounds all great, then today I came to my computer to find an unusable noisy mess. 

AbnerK

Richard Haseltine said:

2) can also be done, at least in part, with the Tone Mapping options in Render Settings' Editor tab.

I wondered that, but, I can't get my head around how changing the settings to get effectively the same light can make a difference. I already pump up the lights to 150000 lumens as a starting point and adjust the exposure. 

I'm trying a spot render now with different filter settings and my next choice was going to be more light and then Photoshop. I'm still confused by why sometimes I get really noisy bits of a render then a line of really clean bits where the noisy bits are where a light hits an object which make you think the extra light causes the problem. I've concluded that the best light is HDRI for darker scenes but that doesn't help when you've got a scene in a room where you don't actually want exterior light. I've done a few scenes where I've removed the walls to light HDRI light in. This scene was only letting in light from an emissive plane. I quickly tried removing the roof but that ruined the lighting. I'll have to play around with getting the balance I think. Thanks both. 

Oh, yeah, iRay. I don't touch 3Delight seems like a headache to save a few minutes and get a bad result. 

algovincian

AbnerK said:

'2' has occured to me but it doesn't answer my question of why I get good, dark renders sometimes and others not.

In my experience, the more indirect the light is in low light situations, the more iterations it will take to resolve (indirect meaning reflected/refracted). Also, many times it has to do with the surfaces of the objects in the scene as much as the lighting. Environments with high-res bump/displacement/normal maps that are reflecting light from a low light area in the scene will take a long time to resolve.

- Greg

WendyLuvsCatz

emitters are the main cause of noise, the more you have the noisier

AbnerK

WendyLuvsCatz said:

emitters are the main cause of noise, the more you have the noisier

You mean lights?

AbnerK

algovincian said:

AbnerK said:

'2' has occured to me but it doesn't answer my question of why I get good, dark renders sometimes and others not.

In my experience, the more indirect the light is in low light situations, the more iterations it will take to resolve (indirect meaning reflected/refracted). Also, many times it has to do with the surfaces of the objects in the scene as much as the lighting. Environments with high-res bump/displacement/normal maps that are reflecting light from a low light area in the scene will take a long time to resolve.

- Greg

Yeah, thanks, I get that, I was kind of taking that as read. I've done several scenes with two figures, the same figures, that is, all the renders had been great, nice and dark but this last one was seriously noise, same figures. My Daz crashed several times yesterday as I was adding and removing things fromt he scene and that reset my render settings then the resulting render was awful. So, I'm really after level playing field type information. Changing the skin materials wasn't part of the equation for me. Thanks though for the imput. It will be useful to someone who is new. 

 

WendyLuvsCatz

AbnerK said:

WendyLuvsCatz said:

emitters are the main cause of noise, the more you have the noisier

You mean lights?

well surfaces can have emission and are not necessarily considered lights

a light really is in fact an emissive surface too if you look under the parameters  you can chose the geometry used

AbnerK

So, I changed a couple things. I removed another wall that wasn't in the picture, removed the emissive plane that was giving me that nice blue light and ramped up the HDRI to its default. So much better. 

AbnerK

WendyLuvsCatz said:

AbnerK said:

WendyLuvsCatz said:

emitters are the main cause of noise, the more you have the noisier

You mean lights?

well surfaces can have emission and are not necessarily considered lights

a light really is in fact an emissive surface too if you look under the parameters  you can chose the geometry used

Well, if it's adding light, it's a light. :) 

WendyLuvsCatz

AbnerK said:

WendyLuvsCatz said:

AbnerK said:

WendyLuvsCatz said:

emitters are the main cause of noise, the more you have the noisier

You mean lights?

well surfaces can have emission and are not necessarily considered lights

a light really is in fact an emissive surface too if you look under the parameters  you can chose the geometry used

Well, if it's adding light, it's a light. :) 

not in DAZ studio terminology 

not being facetious just if troubleshooting  issues one needs to be using the names of the parameters as used in the software in question.

The tool D|S refers to as a light has different user interface settings than the one refered to as an emission surface.

Richard Haseltine

Complex emissive surfaces can certainly be an issue, but a simple shape is usually not such a problem - and if you lower its Cutout Opacity to almost, but not quite, zero it becomes a "ghost light" adding light without being reflected so it can fill in shadowed areas without adding specular highlights.

AbnerK

 

Richard Haseltine said:

Complex emissive surfaces can certainly be an issue, but a simple shape is usually not such a problem - and if you lower its Cutout Opacity to almost, but not quite, zero it becomes a "ghost light" adding light without being reflected so it can fill in shadowed areas without adding specular highlights.

I wondered wether or not the cutouts could have slowed it down at all. I'd made the planes as simple as possible, I didn't bother with divisions but I didn't think of lowering the opacity of the emissive plane to let HDRI light through, I've made 'ghost lights that way before' but, regular lights aren't rendered so I use those most of the time. :)  Thanks for that, Richard. The render was a hundred times better with the increase HDRI and the removed wall though. 

skinklizzard

just as a side note, tone mapping does not in any way effect the amount of light in your scene.

Iray works basically by bouncing simulated light beams around your scene, the more light there is to bounce around and the better the coverage of the light sources the faster the render.

tone mapping then takes the resulting image and just adjusts how bright it looks (simplification) the same as if you took a 32 bit image and edited the exposure in photoshop.

meganappstate

 

AbnerK said:

​Any tips and tricks for clean, dark renders anyone?

Tutorial -- Shooting Day for Night