All language subtitles for nuk214-class07

hello everybody and welcome to class 7 of Nuke 2 14

class 7 is the first part of a two part class

involving channels and layers in multipass compositing

uh the first class is gonna be a little less

production heavy than uh

than we're used to

but it's really just to get kind of a foundation

and firm understanding of

of what channels are and how nuke works with them

or rather how you can work with them in nuke and uh

really get the most out of the software in order to um

in order to composite efficiently and effectively

and the second part of

the class is gonna be building on all of that knowledge

and all of the knowledge that we've built on so far um

to do some multi pass compositing with some 3D images

that contain a bunch of different render passes that

are common to a lot of different 3D applications

so uh let's just jump right in

um I've just prepared a quick little uh

teapot example

um just to show you that uh

just to show you the basic channels that that new

that new comes with um

the ones that were all used to and the ones that uh

that are common to pretty much every single image uh

format and compositing software

the red green

blue and alpha channels

uh and a channel is

is really just basically a

way of differentiating between different sets of data

um so those red

green and blue channels are the ones that

that new kind of reserves for

the ones that get displayed and

the ones that you're looking at constantly it always

it's always displaying the red

green and blue channels

um by default unless you

you tell otherwise um

but we'll get to that in a little bit

so if I quickly

use the hot keys and jump between the red

green and blue channels

I've split up the

the teapot into its red

green and blue channels and

and laid them out on some cards just so we can see them

and I also went ahead and made

an alpha channel for the teapot

so that we can discuss

discuss a little easier so

so anyway let's just take a look at the

at the teapot here um

and so what I've done is I've used a Kia to

to generate an alpha channel

um that we used to

and then a roto node

just to generate a quick garbage mat of uh

of the inside of the teapot

so we have a solid channel to deal with and uh

so the first thing that we use all the time

um it's called the pre melted node um

and actually uh

this is also kind of prompted uh

from some of the discussions that we've been having on

the forums involving um

overs and pre multiplies and stuff like that

um so this is a great example of what

pre multiply actually does is it uh

it takes the RGB channels that uh

that we have coming from our image red

green and blue

and it multiplies them by the alpha channel which uh

which I have to find with that Kia

so uh if we zoom in really close here

where this alpha channel is uh

is one right here

um and the uh

and the RGB channels are point five

point four and point four

um since that alpha channel is one

oops um when we pre multiply it

those RGB values stay exactly the same however

uh let's pick a point um

where our alpha is

okay right here

point zero four

so what it's going to do when I go through

the pre multiply node

is it's actually going to multiply each one of these

RGB values by point zero four

so as you can imagine

it's probably gonna get pretty dark

um so here we have yeah

point zero three

point zero three

point zero three from what used to be point eight

point eight

point eight

so that's just

uh you know

that's exactly what pre multiply is doing

it's just multiplication

if you go into the node

you can see that it's saying um

the multiply option here is

which channels would you like to multiply

in this case

the RGB channels

and which channel would you like to multiply it by

the alpha channel

so that's the

that's the most basic way

um to use a pre multiply note

and then if we wanted to put it over oops

if we wanted to put it over something like uh

a big red something for instance we use the merge node

and uh let's just make it the same format as our image

here we go so if we look at that now um

it's put that pre multiplied image over the uh

uh over the red background

uh if we plug that into the non pre multiplied version

since it doesn't

it's not pre multiplied yet

it's putting the entire image over over the uh

over the red

um so that's why the

the merge doesn't work properly

unless you pre multiply first

um cause if we look at the tool tip

the over is doing oops

the over is doing um

where's over there it is a plus b times 1 minus a

so it's uh before it does anything

remember your order of operations

um pemdas um

parentheses

um multiplication

um division

addition and subtraction

so um what it's doing first is

the multiplication inside that parentheses

so 1 times a

so um excuse me

so 1 minus a

so it's taking the basically the inverse of the alpha

and then multiplying the product of a and B

or excuse me

the sum of a and B

so then what I've done is uh

is I've split it up into its constituent elements

if you will

um so this shuffle um just takes the red channel and uh

gets rid of everything else except the alpha channel

so now I've I've just got my red and this

shuffle does the green and this shuffle does the blue

and then I just put them all on cards and laid them out

and then if we do a plus

we can see them on top of each other like that

so if I were to

get rid of these

cards and just so we're looking at it in 2D again

it's basically going to look

if I just add them all back together

we get uh the exact same image

so just as an example

let's try and uh isolate those leaves and uh

and grade them so I'm gonna make a new roto node and uh

just uh wrote all these uh wrote all these green bits

just for now so I can see through it

I'm gonna change it to alpha

and do the next leaf

and The Last Leaf

cool so now that's going on top of the alpha channel

that exists already

so we can't see it quite yet

but instead of

outputing to the alpha channel

I'm gonna tell it to

output to a new layer

so we're gonna make it

leaves dot mat

cool so if I I still can't see it

so if I wanna look at it

I can use these menus in the upper left

and this is the uh

these three things choose which layer and which channel

your viewer is looking at

so if I go to leaves now you can see it's uh

it's highlighting in red

it takes the first channel that exists in uh

that particular layer and assigns it red

the second layer

the second channel in that layer will be green

and the third will be blue um

and that's just in terms of reviewer

it doesn't actually um

mean anything in terms of um

how it actually outputs

but that's just how new

uh likes to look at

at channels inside of a layer

so anyway um

now we have our leaves mat

um existing on its own layer and its own channel

I'll switch back to RGBA

and uh now if I wanna change the color of that stuff um

I can just instead of dragging a new mask input and uh

and setting it up the way we're used to

kinda something like uh

something like that

um if that were still the uh

alpha channel

um so we can

you know crank on it that way um

but instead of doing that

because that can kinda get a little messy

and makes your comps big um

I'm gonna go back and put it in line and uh

assign it to output to the leaves layer

and then in the mask input without dragging a new um

without dragging that arrow out

uh into another note

I'm gonna tell it to use the leaves channel

that exists in this pipe as the mask for that grade

so now I can push and pull on those uh

on those leaves all I want

make them warmer or bluer or more red or whatever

reds reds nice

let's do that um

so there we go now uh

you can also manipulate that channel um

let's do that before it goes into the grade

so instead of grading the RGB channels

I'm gonna tell it to grade the leaves channel and uh

if you do that

you can see it

it changes um

it changes the map before it gets into the uh

into the grade that's grading the RGB channels

so let's you can also do that with

with all kinds of other nodes that operate on channels

which is basically all of them

so in for with a filter

a road node

we can erode that channel up or down

depending on what the situation demands before it

gets into the grade that way too so

so I definitely encourage you to

to try and work this way as much as possible

it makes your comps way cleaner and way

way easier to understand and it uh

it nicely puts um

what it's doing in the tool tip or

or in the uh

in the title of the node

so you can see that the 1 in parentheses um

is the one it's operating on

or the one that it's outputting to

and this when there's a slash in there

that means it's being masked by particular channel um

and if you invert that

it puts a little tilde in front of it

um in front of the mask

so you can see that it's

um you know

it's inverting the mat and using that to uh

to be the mask

so now let's just have a little fun and uh

I just found it a little table image

and let's put that on uh

on top of it uh

so the great thing about leaving

the alpha channel alone is it still exists as

it still exists

so we can pre multiply that

and let's just erode that alpha channel too

by one great

so that left eye leaves alone

and then we can merge it on top of the table

and let's move it

oops

on top of the table

let's just make that uh

so we can see it

so let's say we wanted to add a shadow to the uh

to the table right here

uh no problem at all um

what we can do is we can use the uh

the table image itself and uh

and and use that as a way to um

make a make a shadow

so let's go ahead and make a new layer

and we'll call this uh

shadow mat

but we don't actually wanna look at it

we just wanted to create it

and we're gonna copy the alpha coming out

of the um teapot into the shadow mat

and use a grade and have it masked by the shadow mat

and then we'll multiply

we're not gonna see anything yet

um cause I added this transform which we have to

oops make it uh

negative height there we go now we can see it oops

and just we're just

trying to get something really quick and let's pretend

well actually let's see the light is coming from

the front of the table

so what I actually wanna do is

something like that

here we go and I can blur that before it gets there

cool

so uh really

I actually kind of skipped over what I did with

the copy note

the copy note is a way of copying one channel or

or multiple channels really

or uh a layer

which is and a layer is a collection of channels

uh into another pipe

so uh what that does is it takes the a

and puts it into the B um

and you can just read it like a sentence

so what we've done is we're copying channel

rgba dot Alpha to

uh shadow dot MT

so then now that exists in in this pipe and we've

transformed it and blurred it before it got in there

so that's why um

why it looks like that

and then when we merge it on top

it goes on top of everything

and there we go

and now we can use that

and then we can use that mask to do

any number of other things

um down the stream

so how about we put this table someplace useful

um I got a little yard image of Google Images

so let's put it right in front there

for no particular reason um

so we'll just go a over B

and of course that didn't work quite right

I have to reform at that to HD and uh

you know the alpha channel is is completely wrong

so let's uh

let's give this an alpha channel

that should be relatively straightforward

pre multiply here we go

now we've got that over that

and uh let's go ahead and ero oops

erode that uh that table alpha just a tiny bit

nice

and then uh

move that guy up a little bit

move the holster bang down a little bit cool

and we can do the same process for the for the table

so let's go ahead and do that

and we need a new channel called

well actually we can use the same channel

so instead of making a new channel

cause I wanna name it shadow Dot Matt again

um but that one already exists

I'm gonna copy it into the same channel name

but this time it exists in a different pipe

so it doesn't really have any concept of

of what was going on

um upstream

so actually I can even copy this grade node

and there we go

see it's it's doing um the same kind of deal uh

and now the same thing that we did before

and scale

look at it there

so obviously

you know I'm not gonna spend too much time on this um

but you get the idea

cool uh

so the other thing that channels are useful for is a

lot of nodes depend on

depend on arbitrary channels to define other things um

things like motion blur and uh

distortion and all kinds of stuff like that so um

just for fun

uh let's pretend this teapot has uh

boiling water in it and we can actually add some uh

some distortion to um

heat distortion or something like that to the uh

to the background to make it

make believe that there's uh

water boiling in this uh

in this pipe so uh

we start with

let me just start with a I distort node

that's how you introduce um

distortion into anything

um so by default it doesn't do anything um

because it needs well

first of all

that the channels option in the I distort node um let

you know what channels that it's going to operate on

and the UV channels define

how much distortion takes place at a particular pixel

and really what that is

it's not like amount

amount of distortion is a little misleading um

the U is how much it's gonna move a pixel

um to the left or right

and the V is how much it's going to move a pixel

um up or down um

so if we um

a common trick is to use something uh

like a noise function

so luckily new comes with a uh

with a noise node and it outputs the rgba by default

so that's fine

because that's gonna allow us to kinda tweak it and uh

and adjust its size

and get it right before we use it as a

as UV channels

um so that's

that's kind of cool um

that'll be about the right size right around there

and uh to animate that to make it move

cause right now in time it just stays put

you use the uh the Z attribute

so I'll set it at uh at 0 on frame 1 and um

make it fairly frequent so on frame 100 it uh

it's at uh a depth of 100

see that that's a little too frequent actually

so let's change that

let's make it half as much so we go down to fifty

still too much ouch okay

there we go

that looks like bubbly kinda stuff cool

and so what that's gonna do is uh

we'll make another layer and we'll call this one

distort dot u oops

and distort dot u and v

great so this is gonna

this noise is gonna define the uh

the horizontal distortion and then uh

we can copy it and have the next one

define the V distortion and to make them different

I'll just uh

I'll just change the um

change the values in the

z so that it animates differently

cool

so now when I look through the distort node here

and I tell it to use the distort channels

I'll just have them

scale up a little bit so you can see what's going on um

so now it's it's uh

it's moving those uh

moving those pixels

based on the amount of noise that we plugged in

so if I if I disable the V for instance

now it's only doing horizontal distortion

and same thing if I if I do uh

if I disable the U channel

it's only doing vertical distortion

and uh we can have a little fun with that distort note

so you can see exactly what's going on

um I'll just make a quick roto shape here

and another one

here oops I lost it

there it is

and tell it to use the distort channels and I'll tell

uh this one to only do u and this one to only do v

so there now you can see that uh

now you can see that the

the one that was doing U is moving

horizontally and the one that's doing V

is moving vertically

so that's kind of cool um

but I don't actually wanna do that

those back in line and now uh

we want to mask it to just the area of the um of the

of where we want the distortion actually take place

so I'm gonna make a roto node

look through our bottom here and uh

for the time being I'm just gonna tell it to use Alpha

so again I can see through it

something like that maybe

and then this is one of the only times I'll ever use

the uh the blur function of the of the roto node

um just to do something quick

um so cool now I'll uh

now I wanna actually I wanna keep this the same

on the same layer as our other distort channels um

so I'm gonna go distort

and it fills in um

what's already there and I'm gonna name it uh mat MT

since it was on the same layer

it automatically filled in

um it's also affecting the U and the V

so I'm just gonna uncheck those

so now it's not gonna affect the uh

the actual distortion at all

um which uh

so that leaves me with just telling the distort node to

use the distort MT as a mask

so there we go

cool and uh let's just turn that down quite a bit

cause that's obviously a ton

cool

so there we go

um that I hope you um

Learned a little bit about how to use channels

um a little more efficiently and

and effectively

um without having tons of different arrows and pipes

and everything going all which way

and different types of mask inputs and all

that stuff um

using channels efficiently will

not only produce cleaner comps

it will produce more efficient comps

so now we're gonna take a look

at a 3D scene rendered out of V ray

and the great thing about V

ray and other robust renderers

is that you can also decide to have it output

um all the constituent passes that

that made up that final image and uh

and V ray and

and other renders will uh

render it out in uh

in layers into an EXR

because of the way we have V ray set up um

we have to change the color space

um to SRGV so that it knows um

it knows how to convert everything and uh

let's just take a quick look

at some of the passes that come out of it

we have things like uh

we have the depth channel

we've got the global illumination

the diffuse

the lighting

and the normals and all kinds of stuff like that

so now let's just take a let's uh

let's see how to put that stuff together so that we can

manipulate everything um and uh

and put it all back together

so now let's take a look at how to put um

all these passes together so that we

can change each of them independently and uh

engrade them and get uh

the look that we want

so I'm gonna get rid of that color space node for

for now um so it's gonna look a little washed

out just because it's not in the right color space

but it's okay

we can still work with it

so let's just shuffle out the uh

let's start with um

the direct lighting

so um the direct light um

is basically uh

is basically

one bounce of light before it hits the camera

so we're basically looking at

or we're going to be creating the

the light that

um that comes directly from

from all the light sources

so that's not gonna be any kind of like

um color bleeding from uh

from one object to the other

so that consists of the diffuse pass

which is basically just

all the image textures mapped onto um

the geometry without any consideration for the lights

um so if you look here

there's no kind of shading or anything like that

having to do with uh

with the lights

um and the way we calculate um

the first bounce lighting is we multiply that oops

by

the lighting

raw light so the raw light is basically uh

just a grayscale representation of uh

the intensity and colour of the

of the light um

coming from light sources uh

so here the light

coming from the windows is bouncing on the ground

and that's kind of a yellower

yellowish hue and the uh

the moonlight or sunlight or whatever that uh

that I'd put up here is lighting the rest of the scene

so if we multiply those together

you can use a merge node and change it to multiply

and just oops

multiply them together

and there we have the lighting pass

and if I shuffle out that lighting pass

we can see that

when I switch back and forth between them

let that load up

they're in fact exactly the same

so now if you zoom in a little closer

you can see that there's some errors around the edges

and that's because um

that's because we first have to unpree

multiply this by the alpha channel so uh

see when I look through the one that I've done

it's eating in on it a little bit

so let's just go ahead and unpreemult oops

before all the shuffles

let's unpree multiply all the passes

all the layers all

so now we have exactly the same thing

great

so that took care of the direct light

and now we need the uh

the indirect light or global illumination

so if we shuffle out

the um the Ra Global illumination

and we uh multiply that

by our diffuse

and uh that gives us indirect light

which is basically light that uh

light that comes from um

light bouncing off of other surfaces

um so it's a little difficult to see but um

if it were a little more extreme

you'd see some red bleed on uh on this surface

if we look at the ragi

here you go

you can see the red bleed in this corner

that's coming from the red coloration of the uh

of the bricks on the chimney and it

it just contributes a little bit

it's not uh

not a ton but as you can see from just the direct light

um it does add quite a bit

so and we can prove that as well if we

shuffle in our computer gi

so those are exactly the same

fantastic

and now to put those two together um light is additive

so all we have to do oops is add a

uh a merge node and have it do addition

so that's a plus

there we go now we have our um

now we have our direct light

and our global illumination

our indirect light added with our um

added together to produce our overall lighting great

and now we just need to add um

all the other ones together to create that final beauty

pass so let's shuffle out the

um let's shuffle out the reflection

cause that's getting this nice uh

this nice moonlight uh reflection on there

so that's also a plus

I'll just copy this one

there we go

now we have some nice shine on that house

that looks kind of nice

and then um

we kinda missed what's going on inside the windows

that's coming from the uh

from the self illumination

because uh the uh

the lights inside the house

uh or the the bright area inside the house is uh

is in fact um

the light source that I made visible

it's a big area light um

that's emitting light and I just told it to be visible

so if we just shuffle out that uh self illumination

now we get just those lights and just like before

it's all additive so

A+B gets a snap so I take a look

we're getting pretty close

in fact I would say that's about it

um so if you have any other kind of passes like uh

like refraction

um there is refraction uh in

there's a fraction layer in this uh in this image

um except it's empty

so if I go to it refract

you know it's black

because I didn't have any refractive surfaces

um in the scene

it didn't have anything to output to

or didn't have anything to output

uh so if you have any other uh

passes in fact um

the specular light does

does have some value in it

so but just like everything else light is additive

so all we have to do is just add it together

so that didn't make a huge difference

but you know it's there so we should

we should definitely add it

so then when you're all done

all you have to do is just premult everything by the

Alpha channel

oops okay but uh

so our alpha channel got a little screwed up

because we're doing all these shuffles

it kinda lost track of the alpha channel

so um rather than

try and go through this rat's nest of merges

and make sure that the correct alpha channel is getting

shuffled all the way down through the pipe

um what you can do

is just copy the original alpha channel

back down

and there we go

so now if I look at the top and bottom

1 2 exactly the same

and then I can just uh

at this point I would uh

add my color space node to

put it back into the right place

so now what we can do is uh is add grade nodes in um

in key places that we want to be able to change the uh

uh that we want to be able to change the image

so uh let's see

so this is our

so this is why

you should stay organised while you're compositing

so why don't I just go ahead and do that really quick

so now I'm a little more organized

I organized it all and

I laid it all out so it's a little easier to follow

and I also went ahead and named all of these

shuffle notes so that I know what each one is doing

so now I can add my grades at key points and

and name them all

you know appropriately so that I can

keep track of them later

so this is the self illumination grade

um now I could add grade nodes um

you know underneath each of these

but it would be great actually if I could um

if I could label each of these um

if I could adjust the whole um

GI contribution all at once

so let's make this the GI grade

this is the Raji I grade

my diffuse grade

my

raw oops

raw light grade

my reflect grid

and my

specgrade

and also this is my

di which is direct illumination grid

so now when I look at the end of that

let's say I wanted to make the scene

overall just be a little more blue

there's a bunch of different places I can do that

so why don't we try the direct illumination

uh and make that a little more blue

so I'm gonna multiply and make it just a little cooler

so now this is changing the overall lighting

of the scene so I can really push it and

and you can see what's happening um

I can make it overall brighter overall

not brighter whatever

so let's let's stick with blue

and uh change that reflect Grade 2

let's make that blue

little more blue

and I kind of want those lights to be um

to be a little warmer

so let's change that self

illumination grade a little bit

now those are a little lighter

and

I kind of lost a little warmth of these lights a little

bit so actually

why don't I

just turn the gamma of that down a little bit

so by doing that I get a little um

warmth back in there and I can make the gi

compensate

by having that go a little more blue

cool

great so that's starting to look kinda nice

um but I kinda wanna get a little more uh

speculation out of that and I kinda

don't wanna have to go back into 3D to fix it

so if I take a look at this uh

at this spec pass

that's kinda giving me a little bit of what I want

so why don't I just try and

and brighten that up a little bit

there we go now I kind of have little sparklies

um on my whoops on my on my house

maybe mix that back down a little bit

cool

that's starting to look a little spooky

and um

a nice little uh

a nice little trick to take the edge off of uh

off of some of this uh CG is to use a softened node

it's just uh a different type of blur

and it kind of just melts the channels a little bit

and creates a little

well it creates

it softens it basically

it's kind of like a

like this kind of softening

that happens with a soft lens

right now it's a little heavy handed

but if I turn it down to

the right amount

you know we can kind of get a nice effect

so it's a little different than a blur

just turn that on and off

that's nice

so let's say

I wanted to have a little more control over the shadows

well luckily I rendered out a shadow pass as well

it can't really fit neatly anywhere in here right now

so we kind of have to go back into this thing and

and adjust it that way

so let's um

let's first take a look at that shuffle at at that uh

at that shadow pass

and we're gonna wanna use the raw shadow

so this is basically uh

a map that uh

that has the

the shattered areas um

bright and the non shattered areas are dark so um

instead of like

like the way we did shadows in the

in the previous example with the teapot

um we just kind of took that map and made it darker

um we can certainly use this as a mask for the shadows

but rather than doing that um

we kind of wanna use it inside this uh

this assembly

um process so uh

the place that that goes is um

is it modifies the

the raw light pass

so if we add those two together

I can just show you real quick

like if we look here

this area that's in shadow is defined by this area

that's bright in the shadow pass

so if we add those together with a merge node

there now we have the raw light pass without shadows

which is pretty cool

um and then we can um

plug that into our pipeline

don't forget to name it

and look at the bottom

so now our scene doesn't have

any shadows in it whatsoever

so if we wanna dial the shadows up and down

we can just mix that plus back and forth and that kinda

that that'll uh

that'll affect the shadows for us

so we can kinda

change how intense those are

so that's cool um

so that's kind of close to the look that

that we're going for

for the CG element

and this is actually where we're gonna

leave off class 7 um

and we're gonna do the rest of this comp in Class 8

once we've once I've rendered this scene out and

and we have a sequence to look at

cause right now this is just a still um

so in the next class we're going to take this um

this big setup that we've done um

and we're gonna make it into a

gizmo that fits into a pipeline um

and we're also have a special treat

Sean is going to uh

give us give a little presentation on um

this on the render farm that we use at zero um

which we call zinc um

and so he's gonna talk a little bit about that

because we think it's

a pretty cool tool that we've been innovating um

innovating over the past um

over the past many months and uh

we really look forward to

to sharing it with everybody

because it's something that

uh that's gonna go public

uh eventually and uh

hopefully everybody will get to use it

so I hope you've enjoyed the

enjoyed the class

have a little firmer understanding of

of how channels work and how to uh

and how to manipulate them and uh

look forward to the next class

it's gonna be a lot of fun thanks