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How to use Blender Light Groups

chocofur · 2,422 words · 12 min read

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0:00light groups is an amazing feature that

0:02was added to the official blender 3.2 it

0:05allows you to completely change the look

0:07of your rendering after it's finished

0:09you can now save the light sources into

0:11layers and then change their colors and

0:14brightness in this video i'll guide you

0:16through step by step how to do this in

0:18blender so let's jump right into it

0:22i'll be using one of the blender

0:24interior scenes that's available in my

0:26store check out the link in the video

0:27description if you're interested and if

0:29you want to know how to achieve this

0:31rendering quality in blender i've

0:33recently created the art of rendering

0:35master class it will teach you

0:37everything that i've learned over the

0:39past 10 years working as a blender

0:41artist how to achieve the photorealistic

0:43look what is a correct composition how

0:46to get the right feedback and

0:48self-improve all those questions and

0:50many many more are answered in the

0:52master class but now enough with the

0:54plug and let's get back into blender

0:58so step one is creating a light group

1:02and we do this by clicking this icon

1:04here

1:05and under the passes we have the light

1:07groups so we can add

1:09multiple groups to our scenes and we can

1:12also rename them

1:14so this is the group layout i would like

1:16to use in my scene and i would like to

1:19control those lamps individually that's

1:21why i've created this many groups so all

1:24have to do right now is to select an

1:26object like this

1:28go to the object properties and under

1:30the shading settings here we can select

1:33the light group so i'm going to add this

1:35lamp to the first group here

1:38this one

1:39to

1:40this group

1:41now i'm also going to add the kitchen

1:43cabinet to an individual group and i

1:46also have those emissive details like

1:48the oven so i've created a separate

1:51group for this as well

1:53i also have the area lamps in my scene

1:56so let's add them to the groups as well

1:59we select the lamp and again under the

2:02shading light groups i'm just selecting

2:04the area category and the third

2:07last step is adding the sky the

2:10environment to a group so to do this we

2:13click this red icon here and

2:16same story under the settings light

2:18group

2:19we select the environment so i think

2:23now you can see why it's important to

2:25name those groups properly because

2:27otherwise you won't be able to

2:29figure it out where you've put

2:31those lamps and now it's much easier to

2:34control it so all you have to do right

2:37now is to render your image and after

2:39it's done here in the compositing

2:41settings you'll be able to adjust the

2:43lights however before we do that there

2:45are few tips i would like to give you

2:48tip number one is enabling the denoising

2:51data so we do this here

2:54under the passes and data and go to the

2:56denoising data

2:57we do this because when working in the

3:00compositor

3:02the image with the adjusted lights will

3:05be very noisy so

3:07in order to denoise it to the best

3:09possible quality we have to enable those

3:12settings here

3:14and speaking of noise this is tip number

3:16two it's easier to go from the dark

3:18image to the brighter one um instead of

3:21going from the bright one like this to

3:24the night scene it's of course possible

3:26and i'm gonna show you how to do this

3:27but before you render your image i

3:30suggest boosting the strength

3:32of some of the lamps at least 10 times i

3:35mean it doesn't have to be of course 10

3:37times

3:39in every single scene it really depends

3:42on the

3:43environment but as you can see i've

3:46boosted the strength of those lamps 10

3:48times and nothing really changed in the

3:50image and that's because of the multiple

3:53important sample settings i'm not going

3:55to get into those right now i've created

3:57a whole video about it which should be

3:59linked somewhere in the screen but now

4:02with everything set up all we have to do

4:04is to render the image and once it's

4:07done we will jump into the compositor

4:09and i'm going to show you how to combine

4:11everything together

4:14now if you have never used blender

4:16compositor i kind of get it but don't

4:18worry it's really not that hard it works

4:20exactly the same as the

4:23material setup in cycles so when you go

4:26to the compositing

4:28you should see something more or less

4:30like this

4:31so here on the left you can see

4:34the kitchen

4:35lamp details environment the names we've

4:38set up here in the

4:41light group

4:42they are displayed here as well so again

4:45this allows us to easier navigate

4:48through the file through the rendering

4:49and you might be tempted to start

4:52setting up things right away but i

4:55strongly

4:56recommend

4:58saving the rendering results right now

5:01because right now if you close blender

5:03or it crashes for any reason the

5:05rendering result you were waiting for

5:07will be lost and you you will have to

5:09re-render everything again so there is

5:12actually no point in this setup if we

5:15have to re-render

5:16the back image every time we quit

5:19blender but there is a solution to that

5:22and a solution is

5:25using the

5:27open xr multi-layer file format here

5:31so instead of saving to jpeg or png

5:34select the open xr multi-layer

5:36file format

5:38name the image

5:40any way you want

5:43and this file format stores all the data

5:46that you just rendered in blender in

5:49fact we will close blender right now

5:51launch it again load the file so i can

5:53show you the entire compositing setup

5:56from scratch

5:57so after relaunching blender let's go to

5:59the compositing

6:01and let's enable

6:03this use node settings here now i'm

6:05going to press shift a

6:07and select the image input here

6:11i'm going to load the image that i've

6:13saved in the previous step

6:17and you can see it shows here but before

6:20we continue we have to go to the layer

6:22settings here and choose the view layer

6:25and now you can see everything that was

6:27visible

6:28after rendering the image is now visible

6:31here again so i can delete this

6:34node

6:36i can connect them just for the sake of

6:38it here but the most common node we are

6:41going to use here in the compositor is

6:43the output and the viewer node which

6:47allows us to preview

6:48whatever we plug in

6:51so you can see now when i press ctrl

6:54spacebar we can go to the full screen

6:56and

6:57v

6:58and alt v

6:59to zoom in zoom out so you can see after

7:03plugging in different inputs to the

7:05viewer node we now see

7:08the different light groups rendered and

7:11saved in the file

7:13so let's now start combining the groups

7:15i'm gonna start with the environment and

7:17the area lamps

7:19in order to mix them together i'm gonna

7:21press shift a go to the color and choose

7:24the mix node this is another

7:27most commonly used node in the

7:30compositor so if i

7:33add those two inputs here and connect

7:36them with the viewer you can see we get

7:38this result however i'm going to use a

7:40different mix method here and it's going

7:44to be the add

7:46so now

7:48when i copy the viewer node and plug it

7:51in here this is the raw rendering result

7:54we get from blender

7:56you can see

7:58that we have almost everything except of

8:00the light sources like this kitchen

8:03element here

8:04this highlight from the lamp

8:08so we can start adding them or we can

8:10play around with the environment itself

8:12a little bit

8:14the easiest adjustment you can do is

8:17adding the color

8:19and the exposure node and when i just

8:21drag and drop it on one of the links you

8:23can see it highlights

8:24so

8:26let's drop it on the environment

8:29and now when i reduce the exposure you

8:31can see

8:33it completely eliminates this light

8:36source and if i increase it we

8:39get much more light and you can also see

8:42we are getting some of the noise

8:44introduced to the scene that's why we

8:46also have those denoising passes here

8:49from the denoiser data

8:51past that was one of my tips to to

8:54include because we're going to use those

8:56later to denoise the image so

8:58let's revert it and if you would like to

9:01unplug this node just hold the alt key

9:04and drag it out from the link

9:07so as you can see i already combined

9:09those two lamps together so this is how

9:11they look like

9:13and now let's add them to the

9:15environment

9:16so all we have to do is duplicate this

9:18node again

9:20and just plug them here

9:22and now you can see well actually you

9:25can't see let's make them more visible

9:27i'm gonna use this exposure node and

9:30drag and drop it here instead of

9:32using those two links i'm gonna use them

9:34combined and now with this viewer node

9:37selected i'm gonna reduce it so now you

9:39can see we are dimming the

9:43environment and area lamps and making

9:45the

9:46those lamps from from the lights those

9:49light sources more visible i'm going to

9:51copy this exposure node again and drop

9:53it here but now i'm going to increase

9:55its value so you can see

9:58now those lights become more visible and

10:01we can start playing around and

10:03readjusting the scene but what if you

10:06would like to add some color

10:08to those

10:09lamps or light sources well we

10:12duplicate this node again by pressing

10:14shift d and we change

10:17uh

10:17the mode here to multiply

10:19and now with the multiply selected uh

10:22you have to

10:23pay attention to those little dots here

10:25we need to

10:28put our image source to the bottom dot

10:32here and use the upper one as a color

10:34source so now when i start adding let's

10:36say i add this bluish color you can see

10:39it influences

10:41the environment

10:44so in the meantime my node setup became

10:47a little bit larger and that's because

10:49i've added the remaining light sources

10:52to our mix so you can see with this

10:54exposure

10:56node i'm able to control the kitchen

10:58light that we have here if i go

11:02to just minus 10 it disappears

11:04completely so let's use the value of

11:06zero and with this note i'm able to

11:08control

11:09the oven light

11:13which

11:14introduces a lot of noise

11:16unfortunately but yeah this is uh how it

11:20goes when we go from the bright scene to

11:22the darker one because this is our input

11:25image so still i think it's really

11:28impressive how far you can push it just

11:31with those few notes without

11:32re-rendering and re-lighting the scene

11:35um let's just

11:37change the light here to something

11:39warmer

11:41maybe increase it

11:43and one last thing i would like to show

11:45you is

11:47adjusting those two lights independently

11:49so

11:50at the very beginning i've mixed them

11:52together so now when i use this exposure

11:55slider here

11:57both of those lamps become brighter but

12:00if i would like to

12:02adjust

12:03this lamp only

12:05if i remember correctly it was the lamp

12:080 two

12:09so let's yeah it's definitely this lamp

12:12so let's use this note here and simply

12:16um make it brighter if necessary

12:20so the image now looks nice but it's

12:23still full of noise as you can see

12:26and to fix this

12:28all we have to do

12:29is pressing shift a

12:32going to filter

12:34and choosing the denoise

12:37with the denoise node added

12:40let's move it here to the starting tree

12:44and

12:46we connect the noising albedo with this

12:49input here the albedo input the

12:51denoising normal with the normal

12:55and then we move the entire

12:58setup here

13:00and we just plug it into

13:02the final add node here and add it to

13:05the viewer so it's going to take a few

13:07seconds to compute

13:09but the end result

13:13should look pretty pretty good in my

13:14opinion it might not be suitable for

13:17animation but i think for the still

13:19image it's pretty pretty right maybe we

13:22could reduce some of the noise here to

13:25do this you would need to re-render the

13:27scene and add more rendering samples but

13:31as

13:32at least for the preview and let's say

13:34the test how the scene could look like

13:36this looks pretty well

13:38and i think again if we compare it with

13:41the starting result this this is really

13:43impressive uh how far you can take it

13:48if you would like to continue with color

13:50correction

13:51of this image again i've created another

13:54tutorial on that

13:56actually many tutorials they are linked

13:58in the

14:00screen right now but if you would like

14:02to continue uh i just suggest

14:05unplugging the denoise node

14:07uh and keeping it for the final result

14:10so

14:10now let's say we can use the

14:13color balance node

14:14um

14:17rework the light a little bit maybe

14:19brighten the scene

14:21increase the contrast

14:23and once it's done once we are happy

14:26with the result then i would reconnect

14:28the denoiser here i like using the

14:30denoise before the color correction not

14:33after it so

14:35don't plug it in

14:37here

14:38i just use it this way i think it gives

14:40you the better results

14:42um and for the final adjustments

14:46remember you can always use the color

14:47correction settings here so for the

14:49exposure

14:51for

14:52the contrast

14:54um

14:55yeah

14:56these work pretty well you also have the

14:58curves here that allow you to

15:01uh adjust the individual channels of the

15:03image so if you don't if you think it's

15:05too reddish you can just switch to the

15:07reddish channel

15:09uh sorry to the red channel not the

15:10reddish channel and just

15:13well drag it down a little bit

15:16to make it look better

15:19so thank you guys for watching if you

15:21enjoyed this video i really appreciate

15:23if you subscribe to my channel and if

15:24you want to make better renderings check

15:26out my art of rendering master class you

15:29will learn that making good renderings

15:31is not about talent but following a

15:34step-by-step process that always works

15:36and what took me years to understand you

15:39can now learn in a few days if you're

15:41really motivated so thanks again and see

15:45you in another one bye bye

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