All language subtitles for 2月29日 (5)

clean plates are the unseen

visual effects in visual effects world

where artists paint out and remove

objects so you'll never

see them in the film if they've been done correctly

there are

different levels of detail for different productions

so television

episodic and films have different requirements

my background is working in feature films

so we'll be talking about the techniques used for this

level work professionally

by the end of this video

you'll be able to look at the scene and

break down the steps necessary to approach a

cleanplate with modern difficulty

as well as understanding

different methods of 3d reconstruction that we can use

so this is the scene we're going to be looking at

and we have a camera that kind of pushes in here

the first thing that we actually need to do is

establish 3D for basically everything

that is not the object that we're

going to be removing

so we're going to be removing this

object that's in the center

and also flattening the grass just a tiny bit

around it so we need to have 3D for the

area behind and the rocks that are a bit vertical

the three primary techniques we can use are cards

point cloud meshes or a lighter scan

so we need to have a ground plane

and some kind of vertical geometry or

proper 3d geometry for the rocks

and an area that's behind the rocks

if we do it like this instead

this would be the alternative

and this would be kind of a mistake

so if you project this whole image onto just a flat

card

you're going to actually lose the three dimensionality

of these rocks and it's going to feel like

you have a stretch projection

so beginners might make this mistake sometimes

and you'll notice in the projections

they're looking stretched

and that's because they're not actually

building out the geometry properly

and layering it together

so using the first method it looks like this

we get a basic point cloud from the camera track

and then after that we just place some geometry

flat and a little bit

vertical where the rocks are

the second method is trying to achieve the same result

except with the point cloud generator

so if we go to vertex selection

and we select the vertices like this

and then we go to groups and we say create group

it will create

this group here

that we can click on and say base selected

group to mesh

and when you do that

you can get this

geometry that represents across your point cloud

it's a little bit better for organic scenes as well

whereas

cards sometimes could be better for flat surfaces

so this is kind of what that would look like

our last method here is using a lighter scan

which is more accurate than the point cloud mesh

and this can be captured using an iPhone

Pro which has a lighter scanner

built in and we can reconstruct 3 scene

using this depth data that comes from a laser

so this is showing where the lighter scanner is

on an iPhone and this is me using Polycam

just shooting some lighter and getting a capture

so it's really easy

you just basically film

and it uses the lighter scanner in the back

you can also use the

photogrammetry mode if you don't have the scanner

and that will also give you a high

quality model out of the application

so polycamp is a sponsor on this video

but I thought it would be a good fit for this channel

because I've been using their software for a few years

and I think it's really convenient

to have a lighter scanner in your pocket

being able to capture larger environments

either for lining 3D up

or doing projections directly

the photogrammetry side is really good for

assets as well

to get detailed assets

and not have to worry about the processing time

or dealing with that on the computer

now I did use a lighter scan for this specific project

even though we could have done it with either

of the methods there but

basically one thing you need to do is delete the

object that you're trying to

clean plate out

because we don't want to project onto this

so basically what I did was bring it in

blender and delete the faces

and you get a geometry that looks like this

but after that you can

go to the

vertices and just merge them all to the center

so you can do this in Maya as well

it doesn't really matter

you just need to basically fill the gap

so that we have a solid

geometry that we can project onto

so you can see here I just merge the vertices

and that's basically how we get

a mesh that we can project onto

but not on the object that we're removing

so that's kind of what we got

and it doesn't matter that the texture stretch

because we're not actually using this

texture that came with the lighter scan

so one important principle is to

use what's real and use multiple projections

so if I just do a very simple projection setup here

with one projection

we can see something like this

so I go to the last frame here

and I'm projecting this image

so just to quickly run through it

I'm just doing a frame hold here

and I am painting out on that frame

now normally you would do an undistored

and you would do your paint

and then you would redistored at the end

but since we're dealing with grass and

really small details and everything is in

center of the frame

and it's an iPhone which has low lens distortion

relative to other lenses

I've basically just turned them off here

because the sampling is

kind of making it a little bit blurry

which we

don't have to do if there's no noticeable sliding

so that's just a quick

thing to point out

but anyways we have a frame hold

we have the paint

and projecting onto the lighter scan that we've taken

and this is kind of what we have

but the idea is with multiple projections

is to use what's real from different angles

and so from our first angle here

we see that this rock is actually covered

by the object that we're trying to remove

but on the left side we see this rock that's uncovered

so when we're painting it out

we're actually kind of having to restore

the rock that's here

but if we actually go earlier into the video

and we go backwards in time

we can actually see that rock

so we don't actually want to make up what's there

because at the start of the video

we're kind of losing detail if we do it that way

so rather

what you want to do is do at least two projections

if not more to establish

as much real information as we can

so here we might project the left side to get

to this detail

and then more towards the beginning

before the rock gets covered up we would project

another projection here

and basically

you just have multiple patches of projections

that you layer over

just a over B

after that point

another

technique that we need to keep in mind when doing clean

plates is to dissolve your patches

so a lot of times when you're doing projections

one projection will only work for like a certain

portion of the frame

which means like your geometry might not be completely

perfect or you might see

from a slightly different angle of that geometry

so the projection doesn't work from every single angle

and that means we have to be kind of dissolving to

account for those perspective changes

now this can be a bit difficult to describe

just through a video tutorial

because you really have to see the really

small details

and parallax shifts that are happening in footage

which takes a lot of like scrubbing back

and forth and looking very close

so the best way to actually learn

this is just by practice and actually

running into problems

but I'll explain the example quickly here

kind of where we use this example

so up on this part of this pre comp

if you look at this rock towards

towards a certain frame

it starts to look a little bit flat

which is actually not what it looked like in

the real plate

so if I compare to the real plate

you see the angle of this corner here

it's a little bit different it's kind of being shifted

and so this is where we need to create

multiple patches to make sure that

the angle is changing with the

perspective and the parallax that's actually

in the real geometry

so your geometry will never be 100% perfect

100% lined up

so that's where the 2d techniques

and also dissolving multiple projections comes in

so if we look here

if we go towards the end of the shot

what I did here is a patch

so if I disable it

and I go to this frame and I reenable it

you see I'm kind of correcting

where our perspective started to shift

and kind of just putting a patch over this area

which is bringing some sharpness back as well

now

this projection actually only works for a few frames

if I go backwards in time

we see that it

starts to become a little bit flat again

and so either

there's multiple ways you can correct this

you could use tools like an I transform

so if I create an I transform node

you can get this on the Wikipedia

if you just type an I transform

you can use a grid warp

and you can use other

just 2d tricks to kind of force the perspective

meaning you would take this corner and just

shift it over

just a tiny bit

so that it kind of matches with the plate

so if you look at the plate

we could just shove it over a tiny bit

and kind of correct the angle that's not correct

with the geometry and projection

so you would use these just before

you project it

so just before the Project 3D

you kind of correct the patch

the other way to do it is to use another projection

so what I did here

was I go backwards in time where it starts to break

usually with patches you want to see

like what's the last good frame

that's kind of working and then

go backwards in time

and where it starts to break

is where you're going to have to do some more work

so you would create a patch here

and you would dissolve forward in time

to create that

seamless transition

so it's pretty difficult but it takes practice

so we can look here at what I did

so I go to the key mix

and what I did here was actually

restored some of the original plate again

after I've done some projections

so I kind of bring it back

and then I frame hold that and create a new patch

and so this is going to work for just a few frames

this is like

only 5 frames that we're actually using this new patch

so if I look at the merge

and we see what that change

if I disable it and enable it

we see that we're just correcting the angle

on just a few frames just to get that

perspective to work

another thing we want to do is to hide your tracks

so that is to say

we want to basically try to blend

our patches in a way

that the viewer is not going to perceive

that we might be losing a slight amount of parallax

through our projections

so for example if we're projecting out the grass

grass is gonna have like

you know

an infinite amount of parallax planes because each

piece of grass technically has

parallax in front of the other

now

unless we plan on replacing the whole ground with CG

grass and that's

that could happen

on a film where you just use CG grass

you might have to come up with other ways to kind of

fake that parallax

and so

the two main ways of doing that in this scenario

would be either to have a card

that you have lots of subdivisions

so if you create a card

and you were to increase these

rows and columns to a high number

and use a displacement

so you could use a displace Geo

with like a noise pattern like really small

you could do it that way and you could kind of

just mess up this card a lot to kind of give it

some little

spikes to simulate that movement of the grass over

each other the other way is to just

blend the edges where that

parallax issue might be obvious

and so in this case that's kind of what I did

I just took a roto shape and I

use a fractal blur

I'll attach it

in the description where you can get this node

essentially what it does

is it just if you have a blurred alpha like this

or a sharp alpha I suppose

and you look at the alpha

it's just breaking up the edge through noise

so it's kind of gonna make it harder to see

where we place that CG patch

over the real footage

and that's gonna help us kind of blend across

what we're trying to add

so this is kind of what I add over

and I'm putting this over the shot so we're kind of

replacing some different things and cleaning it up

and we're also flattening the ground a bit

because originally there was a hill here

so I kind of flattened it so there would be

less of a hill

but I'm also just using this technique to kind of

break up the edge

so that's something that you can keep in mind

just to hide

any areas that the parallax is going to change slightly

so the last concept we'll talk about is

projecting from the maximum resolution

point of view

and all that means is to

find an area that is

the highest amount of pixels for what we're projecting

so if we're here at this sequence and we go further

if we're projecting this rock for example

we might want to go closer to it where

this is actually bigger on the screen

because it means that there are more pixels

meaning it's higher quality

especially if we were

walking even further away than this

this rock is gonna get really small

so if you project from there

and then we walk really close to it

you're gonna see that it's gonna become blurry

as we get closer and closer

so in general we want to be

at the closest point of view

where we still can see things

and that's gonna be where you project

now if your perspective changes too much

that's where we go back to the technique

we talked about earlier

where we do dissolves between the patches

so that we don't perceive any

color changes or perspective

changes being stretched from a different angle

that's about it for this tutorial

so if you guys liked it

make sure to hit like and subscribe

and for anyone who wants the project files

these will be added to nuke202

so if you've already taken that class

you'll have this additional project added

and you can play with it there

if you're a

complete beginner looking for a full course on the 3D

system in nuke

I'd recommend checking out nuke22

because we cover concepts such as camera movements

parallax tracking

triangulation

camera projections and a lot more

so you can go check that out on composingacademy

com and the link is in the description