Wild Tricks for Greenscreen in Blender

Summary

This tutorial explores the process of integrating green-screen footage into a 3D scene using Blender, an open-source software. It covers keying out the green screen, placing pre-keyed elements, and stabilizing footage with motion tracking. The video also delves into techniques for projecting footage onto geometry, creating realistic camera movements, and matching lighting to seamlessly blend the composited elements with the original scene. The summary concludes with exporting tips and a nod to the creative potential of such technology for indie filmmakers.

Takeaways

• 🎨 Key Takeaway 1: The tutorial focuses on using Blender, a free and open-source software, for green screening and compositing techniques.
• 🔍 Key Takeaway 2: The compositor is used to key green screens by placing a key node between the movie clip and composite, adjusting settings for optimal results.
• 📸 Key Takeaway 3: Pre-keyed images can be imported as planes in Blender for easy placement in a scene, with natural shadows, reflections, and occlusions.
• 🚶 Key Takeaway 4: Animating the camera can create issues with the illusion of depth when subjects walk away, so keeping the subject stationary or using reference empties is recommended.
• 🔄 Key Takeaway 5: Motion tracking can be applied to stabilize footage by parenting it to a camera, effectively canceling out the camera's motion.
• 🌐 Key Takeaway 6: Footage can be projected onto 3D geometry using an emissive material and UV project modifier, making it appear as part of the scene.
• 📹 Key Takeaway 7: The process of normalizing footage involves adjusting the scale to maintain the illusion of the subject's original motion and size.
• 🏙️ Key Takeaway 8: The digital environment can be extended or modified to create the illusion of a larger space or different camera movements.
• 💡 Key Takeaway 9: Lighting is crucial for integrating the green screen subject into the scene, with adjustments made in Blender's Eevee render engine.
• 🎞️ Key Takeaway 10: The final compositing step involves keying out the green screen and masking the subject, with the use of an alpha channel for transparency in the export format.

Q & A

What is the purpose of the script?

The script is a tutorial on how to use Blender, an open-source software, to create a shot involving green screening and compositing.

What is the first step in the green screening process mentioned in the script?

The first step is to place a key node between the movie clip and the composite in the compositor and click on the green screen to begin the keying process.

How can one import footage into Blender as planes?

To import footage as planes in Blender, you can press F3, type in 'import images as planes', find the footage, select 'Emission', and it will be imported.

Why is it important to activate 'Images as Planes' in the preferences?

Activating 'Images as Planes' in the preferences allows the user to consistently import images as planes without having to do it manually each time.

What is the issue with animating the camera when the subject walks away from the camera?

Animating the camera can disrupt the illusion of the scene because as the subject moves away, they appear to rise and shrink, which does not match the original footage's perspective.

How can motion tracking be applied to stabilize footage in Blender?

By applying the motion tracking data to a camera, and then parenting the footage to the front of the camera, the footage motion cancels out the camera motion, stabilizing the scene.

What is the advantage of using a UV project modifier for projecting footage onto geometry?

Using a UV project modifier allows the footage to stick to the geometry and move with the camera, even if the original footage was handheld.

How does the script suggest dealing with footage where the person walks away from the camera?

The script suggests selecting the footage, parent it to the camera, and then scaling it up and down to normalize the size difference as the person walks away.

What is the purpose of adding a new camera in the compositing process?

Adding a new camera allows for additional camera movement and the ability to look around and tweak the camera angles while maintaining the existing camera movement.

How does the script suggest improving the integration of the green screened subject with the digital environment?

The script suggests matching the lighting by adding digital lights to the scene and adjusting the material settings to better integrate the subject with the environment.

What is the recommended export format for pre-keyed green screen footage in Blender?

The recommended export format is uncompressed TIFFs, which include an alpha channel for transparency data, providing the best quality for pre-keyed footage.

Outlines

00:00

🎨 Green Screen Compositing in Blender

This paragraph introduces a tutorial on using Blender, a free and open-source 3D creation suite, to composite green screen footage. The author discusses the process of keying out the green screen using the compositor and suggests a proper tutorial will follow. They emphasize the importance of good green screen setup and demonstrate how to import images as planes for pre-keyed characters in a scene. The tutorial also covers the use of reference empties for motion tracking and stabilizing footage, as well as the creation of 3D objects that integrate with the green screen footage to create a realistic composite.

05:01

🚀 Advanced Green Screen Techniques and Environment Setup

The second paragraph delves into advanced techniques for working with green screens in Blender, including the use of F-curves for animation, the creation of masks for isolating subjects, and the integration of lighting to match the green screen footage. The author explains how to manipulate camera angles and movements to create dynamic shots, such as having the character appear on an elevator or flying around a scene. They also discuss the importance of matching the lighting in the digital environment to that of the green screen footage for a seamless composite. The paragraph concludes with tips on exporting the final composite with an alpha channel for transparency and the benefits of using Blender for indie filmmakers.

Keywords

💡Blender

Blender is an open-source 3D creation suite that supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing, and motion tracking, even video editing, and game creation. In the video's context, it is the primary software used to demonstrate how to create a shot with a green screen, highlighting its compositing and 3D modeling capabilities.

💡Green Screening

Green screening, also known as chroma keying, is a technique used in video production to superimpose actors or objects onto a different background. The script describes how to key green screens in Blender, which is essential for creating realistic composites where the subject appears to be in a different environment than where the footage was actually shot.

💡Key Node

In the context of the script, a key node is a component in Blender's compositor used to isolate certain colors (in this case, green) from the footage. It's a fundamental part of the green screen process, allowing the removal of the green background to replace it with another scene.

💡Pre-multiply

Pre-multiply refers to a method in compositing where the green screen footage's color channels are pre-multiplied by its alpha channel, which is crucial for correctly handling the edges and transparency when keying out the green screen. The script mentions converting to pre-multiply to improve the visual outcome of the keyed image.

💡Emission

Emission in Blender refers to a material property where an object emits light as if it were a light source. The script describes using emission to project the green-screened footage onto 3D geometry, making the 2D image appear as part of the 3D scene.

💡UV Project Modifier

A UV project modifier in Blender is used to project an image or texture onto a 3D model based on the model's UV coordinates. The script mentions using this modifier to make the green-screened footage stick to the geometry, adjusting the scale to match the camera's perspective.

💡Motion Tracking

Motion tracking is the process of analyzing video footage to determine the position, orientation, and motion of objects within the scene. The script refers to a previous tutorial on motion tracking in Blender, which is used to stabilize footage and integrate it with 3D elements, ensuring that the green-screened subject appears to interact naturally with the 3D environment.

💡Eevee

Eevee is Blender's real-time rendering engine that allows for quick previews and final renderings with advanced lighting and material features. The script mentions using Eevee to match lighting color and intensity, which is crucial for integrating the green-screened subject with the digital environment.

💡Masking

Masking in video compositing is the process of selecting a part of an image or footage to isolate it from the rest. The script describes using a masking workspace in Blender to refine the green screen key by manually isolating the subject from unwanted background elements.

💡Compositor

A compositor in Blender is a node-based editor used for combining various elements of a scene into a final image or sequence. The script details the process of setting up a compositor to key out the green screen, add masks, and composite the final shot.

💡Alpha Channel

The alpha channel in video and image editing refers to the transparency information that allows for the separation of an object from its background. The script emphasizes the importance of choosing a format with an alpha channel for exporting the pre-keyed footage to preserve the transparency data.

Highlights

Introduction to using green screens in Blender and basic keying process.

Emphasis on starting with the fun part: placing pre-keyed people in your scene.

Using the 'Import Images as Planes' feature to integrate footage with emission settings.

Instructions to activate the 'Images as Planes' add-on in Blender preferences.

Detailed explanation of aligning feet and integrating natural shadows, reflections, and occlusions.

Challenges with animating the camera and maintaining the illusion of stationary subjects.

Using motion tracking to stabilize footage and apply camera motion.

Leveraging the point cloud from motion tracking to model geometry that aligns with footage.

Projecting footage onto geometry using emissive surfaces and image textures.

Utilizing the UV project modifier for accurate projection and integration.

Parenting footage to the camera for dynamic scaling and consistent alignment.

Techniques for normalizing handheld footage and adding new camera movements.

Importance of lighting and matching digital lighting with on-set conditions.

Tips for masking out unwanted areas using Blender's masking workspace.

Exporting pre-keyed elements with alpha channels for transparency data.

Optimizing viewport performance with lower resolution proxies.

Recommendations for lighting green screens: ensuring flat and even illumination.

Encouragement for indie filmmakers to explore the potential of Blender and similar technologies.

Transcripts

okay part two of me trying to explain

how to make a shot like this in in free

open source software blender and uh

today is green screening here we go so

i'll have a proper tutorial on how to

key green screens in blender at the end

here because look okay in the compositor

just stick a key node between the movie

clip and the composite and click on the

green oh and convert pre-multiply to

make it actually look good and if it

doesn't you probably didn't like your

green screen good but i want to start

with the fun stuff because there's a

bazillion green screen tutorials already

out there so how to place pre-keyed

people in your scene so hit f3 type in

import images as planes find your

footage select emission and there you go

if you don't have images as planes

already activated open the preferences

activate it in the add-ons tab and then

maybe save preferences to keep it on by

default so i don't have to say this

every time now you can line up the feet

and yeah yeah i've gotten a haircut

since then but you have natural shadows

reflections occlusions you can you can

even animate the camera a little bit

until the subject walks away from the

camera and then things get weird nothing

lines up anymore and that makes sense

because as far as the footage is

concerned as they go into the distance

they're just rising up and shrinking and

animating the camera blows the whole

illusion so you can just have your

person stay stationary and it can be as

simple as that or you can set up two

reference empties and try to animate the

footage so it cancels out the person's

motion parent it to another you can try

to match up the person's original motion

that's annoying and not good and don't

do that instead i i recently did a

motion tracking tutorial uh link links

below so let's build off of that first

off if you track footage apply that

motion to a camera then parent that

footage to the front of the camera it

stabilizes the footage because the

footage motion cancels out the camera

motion because i mean if you think about

it of course it would in fact okay so

this is a tangent but remember the point

cloud we got from the motion tracking

tutorial model some geometry based on

that so it just intersects the reference

points now it'll line up with the

footage but this is still just a camera

overlay wouldn't it be cool to actually

stick that footage to the geometry give

the object a new material give it an

emissive surface and make the base color

an image texture just loading your

footage set the vector to window that'll

make it fill the camera view oh and

don't forget to give it enough frames

and turn on auto refresh now projects

right onto the geometry as long as

you're in the camera view it always

projects from wherever you are that's

kind of weird we want it to stick so

just use a uv project modifier using a

uv map and the camera now if you go back

to materials and use uv instead of

window it'll project the footage from

the coordinates of the camera although

you might have to change the modifier

scale to match your footage a little bit

and subdivide the object but now it's

stuck to the geometry even if your

footage was handheld now it's normalized

you can add a second camera and animate

some new camera movement uh obviously

works best if you stay close to the

position of the original camera but this

can be super useful technique you can

digitally extend out your tiny practical

set put in a big crane move that'd be

impossible to film in your garage this

is this is one of my favorite things

because it really lets you rework almost

every aspect of a shot in post it makes

compositing easier too because you're

not just dealing with 2d layers of 3d

life it's actually there in 3d space

which is a lot easier for my brain to

wrap around oh and since it's an

emissive texture radiating light if you

have an object in there the texture will

actually light the object with

directional accuracy within reason what

that also means is if you shot your

footage handheld you track it and mount

the foot to the front of the camera your

person will be stationary he's still the

same issue as before though if they walk

away they'll shrink up into the air so

here's what we do select the footage

then shift-click on the camera hit

control p to parent the footage to the

camera then control c copy both the

location and the rotation you might you

might have to activate the copy

attributes add-on if you haven't already

it's a very good add-on now tab in it

edit mode hit gzz to slide the plane out

along its local z-axis go into the

camera view and scale it to fit the

frame perfectly now since the origin is

on the camera when you scale the footage

it gets bigger and further away in a way

that perfectly cancels itself out from

the camera's point of view cool huh so

what do we do with this well scale it up

and down so the front of the foot is

just almost clipping into the ground

turn on auto keyframing go a few frames

later and uh and scale it again do the

whole shot this process goes pretty

quick if you can't see their feet give

it your best guess it's really forgiving

and because of trigonometry or something

like that the scaling is actually

normalized and you have your person

walking around the way they actually

were on set in fact look at this this is

from the dynamo dream teaser and because

of this process you can see the footage

not only automatically scales to cancel

out her size difference as she walks

away it also correctly places her in the

right place in the scene crazy just from

lining up the feet once you start 3d

tracking everything just clicks into

place that's a lie a lot of things don't

but this this thing did so so let's

start laying out the environment i'm

going to start with some walkways

intersecting those tracking markers

everywhere she goes maybe maybe block in

some future buildings this is keying not

modeling so we're going to go fast and

loose and let's cheat a little so at one

point caitlyn stops and backs up a few

steps in the digital environment i have

this happen right after she walks behind

a wall and i can just add a couple

keyframes to the camera to make it

continue moving forwards as she walks

backwards when she pops back out we can

use that same bit of green screen again

so we have it feel like she's exploring

a larger space it's cheap but it's fun

or oh okay at one point i have her kind

of rotating in place on her heel i'm

going to add an empty right under her

feet parent the camera to it and

okay so constraints can get funky so i'm

going to convert it to an f curve here

now it's actually animation data instead

of a constraint and now it lets you

parent the camera to the empty and

keyframe it at the start of her turn

rotate the camera add another to the end

and now it looks like she's staying

still but the camera's moving just just

a fun trick if you want we could parent

that empty to a platform and now she's

on an elevator

[Music]

this is also a great time to start

matching up the lighting you can see she

passes a light source here so i'm going

to add a digital light to the scene to

help integrate her a bit if you figure

this out ahead of time you can have

digital objects casting actual light on

your actors eevee also makes it really

easy to match lighting color and

intensity random tip if you're setting

up lights and stuff in eevee and notice

your footage is casting big shadows go

into the material settings and change

shadow to alpha hash and it works a lot

better now so a very exciting thing is

that this process gives you a ton of

freedom to tweak the camera if you want

i like shooting a bit wide so i can more

easily line up the actor's feet with the

floor and then zooming in a bit with the

virtual camera or add a whole new camera

flying around while the original is

still doing its thing obviously you have

to stay in front of the footage you can

tell it's 2d but it's more forgiving

than i expected what i usually end up

doing is just parenting a new camera to

the tracked camera so i get all the

existing camera movement but i can also

still look around and tweak the camera

however i like well okay ian you say

with the voice of an old man who's seen

more than we can ever dream how do you

get this green screened element super

easily open a compositing workspace

reusing nodes add a movie clip and

loading your footage ignore the render

layers we're going to connect straight

to the composite the composite knows the

final node it's what will be saved when

we hit render if you control shift click

on a node it pops up a viewer node that

shows us what we're doing v and alt v

zoom in and out and the alt plus scroll

wheel lets you pan it's not very

intuitive but you get used to it under

matte add a keying node and slide it on

in there you'll have to update the

viewing node to see what you're doing

and this is the big green screen bit

select some mid to darker green now just

slide up the clip black to get rid of

stuff you want to get rid of and slide

down clip white to preserve stuff you

want to keep ideally you want to keep

these numbers as close to default as

possible doesn't look good let's add

some sauce add an alpha convert note hey

hey sometimes that's all you need but

often you'll have to tighten things up

by eroding the mat a couple of pixels to

get rid of like that fringe and this is

usually enough for me but you can tweak

all the other stuff screen balance and d

spill balance can be great to tweak and

a negative feather distance can

sometimes help if you have a really

messy key just try not to overdo it i

don't know what kernels do if you slide

something in direction it looks better

do it okay but what about all this stuff

around the borders we have to mask it

out which is also easy open a new

masking workspace uh loading your

footage and control click to add a mask

circle your subject and click toggle

cyclic to close it you've just created a

mask with control handles and you can

move them just like anything else in

blender hit a to select them all or b to

box select g to grab arch rotate s scale

all that good stuff hit i to add a

keyframe then go a few frames later move

the mask and hit i to add another keep

going surrounding your actor it doesn't

have to be perfect you're just trying to

isolate the actor from all that other

garbage hit alt s and you can control

the feathering if you want under mask

display you can turn on overlay to see

what it'll look like if you want to add

another mask be sure you add it to a new

mask layer you can even make them

negative oh yeah also okay if you hit

tab you're in the tracker what can you

just control click on a distinctive

point track it tab back to masking

select points you want to attach and hit

control p to parent them to the tracker

yes try to do that in after effects no i

oh no i know you can it's just slightly

easier here i didn't mean to please now

jump back into the compositor and add a

mask node using our mask and drag it

into the garbage matte input if it

appears off make sure your project

resolution matches that of the footage

this is important also they assume

you're rotoring out the garbage instead

of what you want to keep so use an

invert node to flip it all around and

there we go looks gorgeous

now we export it the trick is picking

the right format since we're pre-keying

this we need a format with an alpha

channel included that's that's

transparency data i'm not an expert but

i did try every combination i could

think of and uh uncompressed tiffs gave

me the best frames per second what i

recommend is using two versions one full

res and another at like one third

resolution so your viewport doesn't get

bogged down when it's time to do the

final render just replace the textures

with the full res version and it's all

good oh and i should have mentioned this

earlier but if you're importing an image

sequence just select all the images and

make sure anime image sequence is

checked there you go so i i hope this is

useful there's a ton of other stuff that

can be said about lighting green screens

and all that but mostly it comes down to

making sure you have enough light and

the screen is lit as flat and evenly as

possible

i'm just always really excited about the

possibilities of of technology like this

and what it can do for like indie

filmmakers huge huge thanks to the folks

over on the patreon lots going on over

there lots of tutorials i've got a video

going through the entire making of this

shot and lots of assets you can use

rigged photo skin dudes plants rocks

burger textures like waterfalls steam

fire rain all that it's been we've been

nuts it's been really good um so yeah

thanks for watching