Lighting for low light conditions?

(Lalaland) #1

What are the trick to lighting low level light scenes ?

All my efforts are full of fireflies and take a 1000 samples at least , even more , and de-noise.
De noise always messes up any volumetrics and makes it ugly.

I am seeing scenes from other artists that look great with low light and low samples , what is the correct approach.

In the particular scene I am working on , it’s a concert stage with a lot of colored spotlights and volumetrics , no emission planes and it looks like crap until I take it to 2000 samples with denoise.

Any thoughts ?

Thanks for your time.

(yogyog) #2

Volumetrics KILL cycles render times. I guess without that your scene will render fine at a far lower number of samples.

You could try moving your scene to eevee…

This assumes your using the world settings for the volumetric…

otherwise there may be some way of rendering the spotlight glow separately and blurring away all the fireflies with a (about) 16x16 blur… You could force all the materials to be a matte black material in your spotlight layer, and in the other layer you render without the volumetric in the world settings.

I’m guessing that unticking the “use Environment” in the layer settings will kill the volumetrics on one render layer, but I’ve not tested this.

(Lalaland) #3

yes, but the same applies without volumetrics , obviously its better but still , low light scenes are a big problem for me. Volumetrics look and run much better in Eevee for some reason though.

(yogyog) #4

Multiple spotlights is the sort of thing that can be reasonably easily transferred to Eevee. I think Volumetrics look better in Eevee cos you can see what you’re doing as you set them up.

(Lalaland) #5

Yes, that is true , but I had a problem , All the lights are designed as a real stage lighting , therefore I was using textures on the lights , to get light patterns , multiple spots etc , the textured spotlights dont seem to work in eevee ? I am not very skilled in eevee so I might need to change something for them to work like that .

(yogyog) #6

Hmmmm… yes… I would also like o be able to create a projector in Eevee.

(ruslan k) #7

theoretically speaking… the low lighted scene can be emulated from a fully lighted one with taking into
account what exactly makes the difference. so the expected:

  • almost monochromatic - colors of the objects are hardly recognizable at night
  • the secondary lightning is absent - low intensity of light causes almost no light bouncing
  • non-linear light intensity spread (comparing to day lights) - mid-highlighted areas feels darker (gamma >1)

to do the trick:

  • add some blue color to light source to achieve night-like monochromatic effect
  • minimize bounce to 0 or 1 in Light Paths (Render settings)
  • in post-processing add curve (raise black level), and HSV (lower saturation)

was just playing a bit with a default cube )
not sure if gurus do the same, but post-processing seems to be a reasonable approach

night-scene.blend (563.1 KB)

(sundialsvc4) #8

Definitely think in terms of … first … getting a good, clean render of your stage (carefully saving it along with all the relevant “passes” into a MultiLayer OpenEXR file …). Then … using that data to produce a “low-light conditions” version of it: contrast much reduced, hue-and-saturation much reduced, overall output levels suitably reduced.

And, ironically enough, “no spotlights, so far.” The spotlights are entirely “faked.”

  • The 3D spaces where the light-beam appears need to be occupied by a suitable looks-volumetric texture. (But, there’s nothing in this particular render except the spotlights.)
  • The places on stage where the spotlight hits need to be replaced by unmodified data taken from the original pristine-scene rendered in step #1.

And … it is very much going to be done “shot by shot.” It’s 100%-certain that this stage show will not be conveyed in one shot. It probably will be filmed from a small collection of fixed (or maybe, zooming back-and-forth across the stage on a cable) cameras, each one of which will need to be separately modeled and rendered. The final presentation will consist of a montage of shots taken from each of these cameras, and it’s entirely possible that each of these shots will require attention.

(Lalaland) #9

Could you expand on this bit ?
Thanks for your input :slight_smile:

(Lalaland) #10

I should move this to eevee . the animation will take years to render , one frame is almost an hour on a 1080ti at 1000 samples. Quick ,pretty bad looking eevee render test is 1:28 min .

(yogyog) #11

If it’s only spots and not projectors, I think Eevee will work well for you.

(Lalaland) #12

I actually have loads of projectors , but I will have to redo that …lots of work but saved with render time.
Having said that , eevee for me look so cheap , I dont have the skills

(yogyog) #13

The other option is to use a render farm.

(Lalaland) #14

I have 4 computers and 7 Gpus, so I can bring down the render time , but its still way too much .
I am sure I could optimize a lot if I had the skills.

(yogyog) #15

I’ve used Render.ST before now. They’re pretty good. And there are others. If this is a commission you can pass on the costs.

(sundialsvc4) #16

Render a “clean frame,” as described, with no spotlights. Now, separately render only the spotlights. Use the spotlit images in the Fac input of a Mix node which takes information from the clean frame. Anywhere the spotlight falls, information will be used from the clean frame. (The spotlight data only serves to tell you where the spotlit area is.)

So, you have three things working here:

  1. The clean frame, darkened and desaturated to look like a foggy set.
  2. An appearance of volumetric light cones, however generated.
  3. Original data from the clean frame, superimposed where the light hits the stage.

If volumetrics are turning out to be expensive, you can render white cones that are parented to the lights and moving about under a sun lamp, the cones serving to tell you where the light-beams are. You then composite a suitable texture and take only the texture information. (You don’t need Cycles for this.)

“Almost anything can be ‘faked,’” if you are willing to put extra human-time into it and if you can also accept less-than-perfect results.

A key consideration is that we have made the “clean frame” exposure very easy. There’s plenty of light on “that stage which the audience never actually sees.” This means that the Cycles renderer can calculate a good solution quickly.

I would also very-strongly recommend that you look at Eevee. It continues to astound me.