All language subtitles for 07. Creating holdout matte

in this lesson

we will create our holdout mats to layer

the mushroom cloud behind the downtown buildings

so if we view here at the main background plate

you'll see we have

obviously we

we'd layered

at the moment

we just have the mushroom cloud

sitting in front of these buildings

but what we wanna do is we wanna place it behind it

so what I'm thinking we could do

just to kind of get something in there quickly

is to potentially pull just a quick key

and see if that will help us to

layer things a little quicker

so we can do

is if we hit that tab key and start typing in Kia

we pull in the Kia

and this is just a quick uh this

this key is typically used for things like garbage uh

mats and just rough keying

you're obviously not gonna use this for green screen

and blue screen

like high detailed green screen

blue screen keying

there's there's better uh

cures in nuke for that but uh

for something like this

I think it'll work just fine

so if we view that uh

output and just jump over

actually what we'll do is

I'm just gonna just jump one more step

and then add a shuffle node right after that

and just switch all of the color inputs into the Alpha

so now that way

when we adjust our Kia

we will be able to view

without having to switch over to alpha channel

and then we can switch between the uh the

the alpha channel that we're creating via the Kia

and our color pass

just to see how it lines up with our actual buildings

all right so

if we do Luminance Key

could do Luminance Key

you can see there's various operations here

for this Kia

uh I think what I'm gonna do on this one

is probably the red cure

but let's just go back to color pass

you jump so

this is our red

our red channel

our green channel

and our blue channel

the reason I'm thinking red channel

is because there's just a little more

contrast between the buildings and that sky

so if we switch that over

the red key

and then we just jump back over to our shuffle output

and start dragging that over

you can start seeing what's happening

what I'm gonna do is

I'm also going to invert uh

so it's just gonna be swapping the black and the white

the point being

we want alpha on the buildings

not in the sky

we want the sky to be black

so we're just kind of bringing that over

and close to

right about there

and then we're gonna

see if we can crush that sky a little bit

now obviously

this is getting pretty close

there's not much of a range to work with in there

but I think

for something like this I'm not

I'm not too worried about it um

being an issue

so let's just

put it right up there

and at the moment

you can obviously

there's see

there's gonna be holes and stuff

but just for kicks

let's get this in

and just see what it looks like

so our input from the mushroom cloud

is coming from the scan line render

and it's going a over B over here

so let's hit that tab key

and type in merge

or again you can hit the m key on the keyboard

that'll create your merge node

and I'm gonna set that merge node to uh out

so if I set that out

what it's going to do is

I'm gonna say

on the a input

I want that

mushroom cloud to be held

outside of this mat

and then we connect it to there

and drop that in there

and if we view it at No. 2 now

you can see it

just laid it behind there

obviously there's some hard edges

we don't like that

there's some issues going on there

but for the moment

it will work

I'm just roughing things in

and then as

as we get steps uh

further down you

you just basically

start to uh

clean things up

so at the moment

obviously I just wanted to rough it in now let's

let's see here

if we just back off on that

alpha chair

on the crushing of the Kia

uh we're obviously

unfortunately

oops apologies

we're introducing issues

up here but

that's fine

because what we're gonna do is

we're gonna hold it inside

a quick garbage roto

as well as a couple other tricks

to be able to hold things inside down here

but the moment

let's just get it as approximate as we can

and let's say

somewhere right about there

because obviously

we don't wanna kill the edge completely

now what we're going to do is uh

two things uh

one I want to get

I wanna get a quick garbage mat

that's gonna hold our mat inside there

so if we view here

you can see there's uh

some artifacting going on above

that's fine

so what we're going to do is we're going to

I actually wanna go back to that frame

our keyframe

which was our

our hero frame

so to speak

uh was frame four 28

I do believe

so if we go to frame four

twenty eight

and that seems to be nice and level

that's fine

you can see all this extra garbage going on there

that's fine

that's that's your normal

uh expected

uh leftovers

so to speak

you can actually see it's uh

actually gets worse over here

so you know what

we're going to make a quick adjustment um

where we clamp down on a little bit of that

might we almost

sometimes you'd almost

maybe need to have to animate that uh Kia

but for the moment

let's just see where that lies

now it's cutting out stuff in the buildings

that's fine so we we

what we have here is just a rough template

so to speak

so now if we just drop that in

you can see where it's cutting uh

chunks out of the buildings

and that's okay

what I want to do is

I'm actually going to create

now that we have just a quick garbage mat

I'm going to actually take our tracking information

and create a mat that will match those buildings

based upon our tracking information that we already did

so at frame 4:20 eight

let's take that as our hero frame again

like we were discussing

and I'm going to create

hit that O key to create a roto shape

and let's just

full screen here

I'm gonna go out of the comp view

and what I want to do is just start

adding some points here

uh just kind of following that contour of the building

approximately

not looking for

to be perfect at the moment

and obviously

if you're building this for your demo reel

then I would recommend you spend a little extra time

make sure everything uh

lines up and is nice and ship shape

for the sake of the demo

though obviously

we aren't as concerned about precision

when it comes to every single frame

so let's just keep going down here

bring it over

and up here there down

and then you can quickly just compare okay

where's the

where's the mushroom cloud in relation to this

so we know that we're not roadling

more than what we really need to do and

let's see here

yeah we're basically outside the perimeter

I think that should be fine

so I'm just gonna actually continue it

on down to here and over

and now what we're going to do

just for kicks

I'm gonna actually disconnect this

our garbage mats

and here's the other things you know

you can sometimes get away with these quick tricks

sometimes after you've done it

you realize hey

you know what

maybe it's not worth it

in this case

I'm gonna leave it actually disconnected

we'll leave it there in the

for the moment

in case we need it

since we've created it

you know sometimes you might need it for something else

odds are good

we probably will end up just going with this rotor

so what I'm going to do now is we are going to take it

we're gonna basically steal

uh what we've already done

for our other nuclear mushroom cloud

and I'm gonna copy this section right here

and paste it over here

and what we're gonna do is

you're going to

let's take that up there

well you're gonna treat your roto shape

just like you would treat the

uh the file

the input of

of the nuclear mushroom clouds

so you just gonna connect that in

and then it's gonna run through here

you're gonna need to obviously connect your camera

back to that same camera

and just to make things look a little more tidy

I'm going to

uh obviously

then you wanna connect down to here

but I'm just gonna kinda line things up right there

add a little pipe over there so it doesn't

doesn't look too messy

now what we have going on here theoretically

means that it is being held out by a rotor shape

that should match the movement of the buildings

now here's an issue

this is where you start to see

things potentially slipping

and in this case

it is so your

your track might not either be perfect

or your track might not be quite on

because it isn't

the card is not in the proper depth

so what I'm going to do is

I'm gonna go back to that frame 4:28

just for kicks

and I am going to select my card

and view at that card

and I think I'm going to try

just to see if uh

we can maybe adjust it uh

and push it into the proper place

so you remember all the

the point let's see

where was it

over over here

our point cloud

so we double click that

and kind of see where that's located

I kind of want to just push that a little bit more

into that cluster there

and see if by doing so

we're able to ensure that it tracks a little

little more appropriately

now obviously

if for the nuclear mushroom cloud

maybe not quite as big a deal

you might see some slippage

if you really quickly scrub through it

but over time

you might be able to get away with it

but if obviously

if you're rotowing

you wanna ensure that is spot on

so let's just uh

go back to that view right there

and let's just jump back over here in time

and see where things lay okay

see how you can see

actually we're starting to get it uh

lining up just a little bit better

there's still a little bit of a line

that's okay

we'll uh we'll just push it just a little bit further

so go back to your frame 4:28

just because that's my master

that's mainly why I'm uh

wanting to do that

and just for reference

we can get into that point cloud

and click on that card

so we can adjust it

I'm gonna push it forward to right about there

let's see how that looks

right there

it's full screen

zoom in on downtown and see how it looks

you know what

I think we're uh

pretty close on now

you can see how it's lining up

with the edges of those buildings as we move through

that's that's definitely a little better

obviously you can see now it's slipping over here

so here's the

here's the the the

the gist of it is you're gonna

you might have to go in and do a little more sweetening

but this is

I think for the demonstration

this is close enough

you get the idea

so for the moment

let's take a quick break we've uh

put in our rough hold out mat

just as a recap

and at this point

now we're gonna take a quick break

and we'll come back and begin

uh integrating that mat into the plate

and integrating the overall mushroom cloud

into the background

so it appropriately matches our actual background plate