Original subtitles

In this clip we're going to take a look at combining core

fringe mattes with the keylight tool.

In previous clips we've used the keymix and channel merge

tools for combining multiple mattes.

Combining them with a keylight tool offers a really

great alternative to these workflows.

So let's take a look at our shot.

So inside of our script we are working with the footage of this little

girl on a portable green screen and we have preprocessed the image so that

we can really optimize it for keying purposes.

So here is the preprocessed image.

It has been white balanced, any color cast has been removed,

and the green screen is a little bit more even than it

was before with all the wrinkles.

Now if you're not familiar with the preprocessing workflow,

there is an example of what I have used here; however,

I will go into it in more depth and as well with multiple

different keyers so just the basic of those keyers inside of the

NUKE Green Screen Keying Fundamentals Course.

So let's take a look at the keylight tool itself.

So inside the keylight tool we have a number of different inputs.

We have the source input, the OutM, the BG, and the InM.

So what exactly do those all mean?

So let's take a look at a reference example.

So here we have an example and we're going to pretend that this gingerbread man

so to speak is our little girl in our green screen footage.

So the OutM represents the garbage matte.

So that would be either created with a roto shape or in this

example we're going to be using an alpha channel that has been

dilated so it's a rough matte.

InM is the inside matte or the inner matte.

Another term could be core matte.

So it will be 100% opaque with no holes in it.

The source is the RGB source input so that's the green screen that we

will be plugging into our keylight tool and BG allows us to plug the

new background into our keylight tool, assuming that that is a funnel key.

So let's get started.

So inside of our shot we have a number of different blue backdrops.

So each one of them will build on top of the other.

So inside of it we have a starting tool and then a reference tool,

which is the optimized tool for us to work with.

So I'm going to skip over a couple of steps just because they

involve pulling the basic key and preprocessing.

So here's a preprocessed image.

We pull a brief key with the IBK tools,

but we have to do one last step with them because

this is not an even green screen.

In fact,

we have some non-green screen portions here on the right and left-hand sides.

So we have used the IBK color,

which is our clean plate and made sure that we've retained part of it.

So here is a roto shape.

I've taken the roto shape and isolate it so that our clean plate will

always be seen on the right and left-hand side of screen.

So we've blurred our edges ever so slightly.

We do want to blur edges of all of our mattes just so they don't

have a hard edge and they're better integrated,

back to full color and to the keymix.

So here we have kept the green on the right and left-hand side and

we pull a key and all we're left with is a little girl instead of

the extra stuff on the two sides.

So there we go and now it's gone.

On to optimization.

So the IBK color in this example is going to represent our core matte.

So let's take a look at that and really just optimize it so close

the property bin there and we have the IBK.

Let's take a look at our alpha.

If I mouse over top of these values, some of them are pretty high so 0.

5 is okay.

It's about 5%,

but 18% is definitely pushing our limit so we're going to have to optimize that,

especially for our core matte.

So let's take a look at our gray tool.

So here we're going to use the gray tool to optimize our

alpha so double click on the gray tool,

change it to alpha so we're not changing our RGB and we're going to pull down

on our gamma and if we have any holes inside of our matte,

let's just see, and we do.

So I'm going to bring up the game.

So it's okay.

She is dilating out a bit.

We can change that after to modify it so we're just

going to pull it up a little bit.

I'm going to clip or clamp the white values just so

that I ensure they don't go above 1.

So there are other ways definitely to optimize the alpha.

This is just one example.

From there, back to your regular lights,

double check these values are a little bit better.

Much better, around 2%,

and I'm going to erode at that alpha just a little bit and then blur out

those edges so that when I combine it with the fringe matte that it's

nice and clean and has a nice transition.

So there we go.

So there is our optimized core matte.

Moving on.

So now that we have our optimized core matte, let's take a look at that there.

So there's our core matte and we're going to create the

outside mask or the garbage mask now.

So I have grabbed a filter erode tool and I'm going to take

it and dilate it out so you can dilate it out quite a bit so

it's increasing those numbers.

It's a rough matte so it's okay if it's not perfect.

So that's why we're going to start there.

So there's our core matte and there is our garbage matte.

Next step.

So this is where we get to combine it with the keylight tool.

So I have taken the garbage matte here so that's the outside,

here's our core matte,

and now we're going to combine them into the keylight tool.

So what we want to do,

let's just make this a little bit wider so that we

can see what we're doing here.

We're going to take the source to our original plate.

Actually, not to our original plate,

to our denoise plate or our preprocess plate.

It's really fine.

We're going to do a despill separately, remember?

And we're going to take the OutM and plug it into our

garbage matte and the InM to the core matte.

And we're going to take a look at how we're going to make

sure that the keylight recognizes it.

So here we have in component alpha and out component alpha.

So what exactly does that mean?

So we're going to go back here and take a look at an example.

So here's another reference.

Back to full color and what we are trying to do is we are trying to

make it so that all the artifacting that was on the outside will be

gone and we will keep our core matte.

So we have the InM component as the alpha; we're going to set it to alpha so

that our core matte is retained and the OutM component,

which is our garbage matte will be inverted.

So what it will do is it will get rid of all the artifacting outside of here

and only keep it so that we have the ability to key between these hard edge

and our core matte that's probably around here,

which will give us a nice falloff of our soft edges and motion blur.

So let's see how we can do that down here.

So back to our script and we're going to take a look at our keylight tool in

the property bin and scroll down to the bottom and it says InM component and

that's going to be alpha because we want to keep our core and OutM component

is going to be set to alpha inverted.

So let's take a look at that keylight tool.

So there's our keylight tool.

That's exactly what we want it to look like because now we can

key between here and here; it will keep our core matte while

combining it with our fringe matte.

Moving on to our last few steps now.

So now that we have this set up here, we're going to pull the key.

So I'm going to pull the key, double click on your keylight tool,

select the eyedropper and generally speaking I want to go really

close to our character where her wispies are.

So Ctrl + Shift + left mouse button and drag.

So there we go.

Make sure that we're clicking on there.

There we go.

Nice and clean.

Turn off the eyedropper, turn off the little selection so Ctrl + Shift + click.

And overall we have a pretty nice key in here so

let's take a look at that alpha.

Her alpha is nice and solid and we've retained nice

detail now also in here wispies.

Now if I take a look down here at the bottom,

we have a lot of values in here that are a little bit high.

So we can pull a second alpha.

So let's take a look at that.

We're going to use our keymix tool to do that.

So I have pulled a second keylight here.

You can see it's a little bit better.

It's cleaned up.

I have sampled down here at the bottom rather at the

wispies up top so even though we have optimized this comp

and optimized the green screen, we don't have the perfect key yet.

So here is the nice key for her wispies at the top and a second really

nice key to fix all the issues down here at the bottom.

Now to combine the best of both worlds,

we have taken a roto shape with a blur tool just to combine them.

Again,

nice and smooth transition and keymix them so it's going to retain the nice

key here at the bottom and retain the wispies at the top,

keymix it together, and there we go.

So now we have the best of both worlds.

We're going to merge over top of a checkerboard just to take a look.

We have included the despill here that is just so that we can see what we're

working with to begin with for our edges and overall this is looking pretty

good so it can be refined a little bit further,

but for a quick key we have a pretty great output.

So in this clip we reviewed the inner matte,

the outer matte,

and how to combine the core and fringe mattes together in the keylight tool.