All language subtitles for 03. CG VFX element study and discussion

in this lesson

we will discuss what we plan on doing

to the nuclear mushroom cloud

and various techniques that might be

used to accomplish our goals

so the first thing we need to do is bring in the actual

rendered nuclear mushroom cloud

so we have two elements to work with for this

we have the RGB color pass

and we also have a separate alpha pass

so what we're going to do is bring both of those in

let's go into the no graph view

and hit the R key on the keyboard as a shortcut

or again hit that tab key

and you can type in read

so hit that R key

and you're going to see that we have our city footage

which we've already bought in

we have Nuke Alpha

and we have nuke sequence

let's bring in the nuke sequence first

so select that

hit next and then go back up one directory

hit the Nuke Alpha folder

select Nuke Alpha

and hit open

we've now brought in

as two separate read nodes

our color pass

so let's view the color pass here

you can see right there

is our actual color of the nuclear explosion

and we also have

as a secondary element

our nuke alpha

that corresponds with that nuke sequence

so what we first would do

obviously if we're setting this up to compass

we need to combine the alpha channel

with the color pass

so we can hit tab

and start to type in shuffle copy

and what we're going to do with the shuffle copy

is basically

we're going to pass through the RGB

color information from the nuke sequence

and we're going to then copy the nuke alpha

into the shuffle copy

and basically read that out

so basically

we're just literally shuffling various color inputs

or various channel inputs

and outputting a restructured

uh RGBA pass

so the first step would be

connect the No. 2 input to your color pass

you can see over here

in the properties

RGB right there

is on the No. 2

so that's where

red green blue

then we're gonna connect the one input

to the nuke alpha

and we're going to switch that over

because if you look here

what we have going on

if you color sample it

you're going to see that red

green and blue

were all corresponding

solid white for alpha

but there is no actual alpha channel

so that's fine

so what we're going to do is

we just switch that one input to say

the red channel

or the green

or the blue

doesn't really matter

and now if you view at that shuffle copy

you're going to see

if we full screen this

you're going to see there's color information

so you can see right here

you know your RGBA

so you see there's color information

and a solid alpha

so when I hit that a key

there's an alpha channel right there

red green blue

and alpha now

at this point

we're just gonna leave that as is

for the moment

and what we want to do is

I'd like to now study this explosion

because there are a

couple things that we might want to consider

so for for the sake of studying this

I'm literally just gonna pick a frame of our cityscape

so let's let's just pick something reasonably

uh horizontal

so let's go to frame 1 426

just for kicks

and I'm going to drop a transform note after this

shuffle copy

so hit the t key on your keyboard

that's the shortcut for transform

and what I want to do then

is put an emerge node

so the m key on the keyboard

you're going to do a over B

and first off though

with that city footage

we do need to add a shuffle

and make it a solid alpha

and then just put a or B

so if we view right here

at the moment

we just are dropping

our nuclear mushroom cloud on top of it

now this is just

really rough

we're not doing anything special at the moment

I just want to

visibly see what's happening with this

so what we're going to do in this transform node is

if we just view it full screen here

what I want to do is

the idea is this

this mushroom cloud needs to go

somewhere back behind these buildings

so eventually

we're gonna

need to rotoscope

out the buildings

or somehow extract them

to layer the nuclear mushroom cloud behind

so it's sort of

kind of downtown

but behind those buildings

so at the moment

what I'm going to do

is just scale this down

and again this is just a rough comp

we're not dealing with anything special

uh and there's a lot of things that we're missing uh

in terms of how we're going to set this up

but at the moment

we're just gonna layer this out

and now that we've skilled it down

I think we need to go further

so I'm just gonna zoom out here a little bit

just so we can kinda see

while we work with our properties

uh let's scale it down to point four

yeah that sounds about right for the moment

and we'll just drop it right there

okay so now

obviously there is one thing that is missing

and that's fine

but but as we're roughing this in

we do need to keep in mind that

when you do swap out your alpha channels like this

don't forget that you do want to pre multiply

uh after you shuffle copy

we'll deal with that in a moment

but the reason that you see this little white uh

Halo is because obviously

the color pass is not pre multiplied

against the alpha pass so that's

that's something we'll deal with the moment I'm

I'm not too

uh concerned with it at the moment now uh

just now that we've kind of layered it there

I I do want to see the nuclear mushroom cloud uh

further long in the timeline

so what we're going to do is

uh actually slip it in time

so the idea behind that is let's just

uh get that

get rid of that and I'm

I'm looking at this

and there's a few challenges

obviously but one

the first thing

like I said

we're gonna slip in time

uh is is you look at your frame range

we have frames 1 through 1 UH1020

our frame range for our plate is actually

frame 1 to 7 85

so it's actually

the plate is a little bit shorter

than what the actual visual effect is

and that's fine

the idea behind that is in

when we were studying that plate

let's just go back to the plate here

uh you know

the cameras over here

and then it kinda whips over

my thinking is

maybe it's already just exploded

and they whip over

right as someone's noticing this big old

huge mushroom cloud

um so we'll

we'll basically

we're going to offset these reed nodes uh

the nuclear mushroom cloud

and push it back in time just a little bit

to line it up uh

a little better

now the way you could go about that

are a couple ways

you can either

in the read node

let's say these were already combined

as a single read node

I'd say one of the easiest ways

is just to go up to where frame

and the drop down is

you have expressions

start at or offset

and you can actually then just offset the

or set it to start at a certain frame range

or offset it by so many frames

in this case

since we have two file inputs

I think what I'm going to do is

I'm actually going to offset it

using a node called time offset right here

so it's very similar but uh

we just take that

and after the shuffle copy

just gonna take these

move them up a little bit

and actually

you know what

now is probably a good time

let's just add that pre multiply node

so drop that in

right there

and actually

before we do the time off set

I just want you to see

visibly what happens

so again we're in the wrong

actually let's go back to

that was a framed 4:26

or in that range

that's probably a good spot

now if I turn off that pre molt mode

you see where that

that white Halo is

but as soon as I turn that on

we got rid of that white Halo

so that that fixes our

our issue with that

now uh let's get back to that time offset

so we take that time offset node

and drop it right in there

after that premult

and what it's going to do is

we're going

to slip it in time

so if I just

just for kicks

say negative 100

you can see that now

now at frame 4:26

it's actually technically

referencing frame 5:26 of that nuclear explosion

because it's slipping it back in time

so what we wanna do is I wanna

I wanna go a little further

I just I just like to visibly see uh

how far so we

we actually

let's back that up

we we do have frames

1 through 1,020

so at 7:85 if I want to get a

a larger uh

scaling of the mushroom cloud

I think what we'll do is

we'll slip it

let's say about

200 frames for now

I'm just roughing that estimate

there's no specific number

that I am shooting for

at the moment

but it's a good spot to

kind of work from

now obviously

it's just sitting there

because it's not tracked in

but that's fine

the idea is

I just want to kind of

get a rough idea

of what's going on

I think our nuclear mushroom cloud

approximately

might match up at about

a scaling of

about 40% of the original size

now a few of the challenges

I think will deal with

I look at this and I say

you know what

I think I kind of like the idea

of the mushroom cloud being just a little bit wider

but I want that

funnel like

sort of like

the neck at the bottom

to be a little thinner

so what we're going to do

later on is

we're going to actually do some

grid warping

the Grid Warp tool

you can either again

hit the tab key

and start typing in Grid Warp

which is right there

you can also go over here to the

no drop downs

it's under transform

and unfortunately

it goes off screen right here

but just take my word for it

there uh so

we can just

hit Grid Warp

we can add that

grid warp and

the Grid Warp tool

is basically

an opportunity to take a

uh an input

and warp it to a shape

that you want it to

uh end up uh

appearing at

so for instance

you can actually use this

for face morphs

that's that's a

commonly used tool

for face morphing

like let's say

someone transforms into a werewolf

and something like that

so that's that's kind of

what you would use

sometimes to

transform a

the actor into

uh to match

the movement

of the actual uh

say werewolf

or whatever

but in this case

what we're going to

use it for is

we're going to be actually

stretching out

the overall

mushroom part

of the explosion

and maybe thinning out the

uh the neck

of the explosion

just a little bit

but that will come in

the next lesson

so to do a quick recap

we're just roughing in

and discussing

what we plan on doing

to the nuclear

mushroom cloud

and just a few of

the various techniques

that we're going to be using

to accomplish that

at this point

we'll take a quick break

and we're gonna come back

and we're just gonna

get right in

and begin compositing this shot