>>Sjoerd: Hi, and
welcome to this presentation on our new sky and
atmosphere rendering that was first added
to Unreal Engine 4.24. My name is Sjoerd De Jong,
also known as @Hourences, and in the next
half an hour, we're going to take a look
at the following. We're going to start
off with the basics. I'm going to show
you how easy it is to get going with the new
sky and atmosphere rendering. It simply works. You drag it in, and within
seconds, you're up and running. Then we're going to
move over by taking a look at the various
settings that are available, and then we're
going to step it up. We're going to go
into space and look at how the new sky and
atmosphere rendering adjusts itself to a space view. We're going to take a look
at the material integration of the new feature, a number
of random tips and tricks, a couple of CVars to talk about. And then by the end
we're going to wrap up by taking a brief preview
at the new volumetric clouds that are going to
be added in 4.26. And there will also be
at the very end, a note of this presentation, a quick
recap of all the recent changes and upcoming features. Before we do get
started, I would like to give a bit of credit and
highlight a few contributors. So first of all, a big thank
you to the entire Unreal Engine engineering team. In particular,
Sebastien Hillaire, who is the principal architect
and engineer behind all of the sky and
atmosphere and volumetric cloud rendering that
you're going to be seeing. Also, I'm using a lot of
assets from Quixel Megascans and from our Marketplace. I'm using the spherical shader
from Nightshift Studios, Tropical Jungle Pack
from PolyAsset3D, the Meadow from
NatureManufacture, the Fictional Aircraft
Pack from ModelWorks. And you can see all
that content comeback in this environment,
which is what we're going to be working with. So this is the result
we're looking for. It's a bit of an
alien-ish planet. You can see it has
a double moon there. And this is what we're
going to use as a demo scene to show the sky and
atmosphere rendering. Let's get started. So starting with basics,
it is very, very simple to get this up and running. In fact, we only need
to do two things. We need to work with
the Directional Light and with the Sky and
Atmosphere Actor. We'll switch over
to the environment. Here is the environment you saw
before, but without any light, any sky present. It's a very big world. We've got a little
valley here, a little space we're going to leave the
camera at most of the time. This is our scene. Now, first things first,
a Directional Light. Here's a Directional Light. Let me drag it in a little
bit more towards the center. Switching the view
mode to lit mode. And out of artistic
purposes, I'm going to set the
intensity to 12. But the really
important thing here is that if you look in
the advanced options, it says here, Atmosphere
Sunlight, Yes. So you have to enable that. That registers this
Directional Light as being a Directional
Light, a sunlight, there has to be detected
by atmosphere rendering. Once you've done that,
you're pretty much there. You can go to Visual
Effects, Sky and Atmosphere, drag that in, and that's
really pretty much it. By having done that,
we're immediately there as I zoom out a little bit,
you see get the shading. All the atmosphere
is being rendered. The sun is being rendered. And if you were to rotate the
sun, the Directional Light-- in fact, you can do that
with the shortcut Control-L. If you hold Control-L,
and while holding it, you simply move the
mouse, you can do this. And you can see it
all nicely updates. Now we have evening,
sunset, getting nights. Then you can have sunrise again. So all of that pretty
much simply just works. That's the basics. It's two steps, and
you're up and running. Now, that being said, there are
a number of additional settings we can play around with. As you see in the Properties
that we have over here, there's a few things
that are important. And you're welcome to play
around with all of them, but I'm going to change
the ground radius to 1,000. The important thing to note here on
the sky and atmosphere feature is that it's
physically based, so it tries to approximate
as good as it can a real atmosphere of a planet. So it's important
that it understands how large the planet is. I'm going to put it to 1,000. I have a pretty small planet. This is going to come into
play when we go into space. Right now, more
immediately, though, we've got these three main settings,
Rayleigh, Mie, and Absorption. All of these have to do
with a scattering of light and therefore color
in the atmosphere. So this is affecting how
the sky basically appears. So for example,
Rayleigh scattering is primarily focused
on the scattering from atmospheric gases. Mie is primarily from dust,
smoke, water droplets, that kind of scattering. And Absorption is ozone. So if you were to lower
Rayleigh Scattering to a much lower amount,
you can see what happens. If it's zero, there is
no scattering at all. Essentially, you are
now looking into space. So if you have a
very thin atmosphere, you would have
something like this. And so you can play
around with it. If you increase it,
it gets ever-redder. And you can use this to
create alien environments, maybe simulate a
sandstorm or anything in those kind of directions. Mie Scattering is similar. See, what happens
there is basically you get a lot more
reflection and scattering of light between
the particles that are floating around
in the air, so you get a very dusty environment. And the other way around,
if you bring it to zero, it gets reduced. And likewise, so,
with Absorption Scale. So those are the three
main settings you can use. You can also apply an override
for the Rayleigh scattering color, so a different kind of
alien environment, if you wish. But that's the bulk of it. Now, that being said, where
this gets really, really cool, I think-- the first time
I did this, when I first got my hands on this,
it was eye opening. You can go into space. In fact, the sky and
atmosphere rendering is dependent on altitude. So if you were to go
up with the camera-- and you might need some fairly
high camera settings here. So I'm using Camera Speed six. I've got Camera
Speed Scale at 32. You might even make that
64, or something like that. You need fairly large numbers. I'm going to point the camera
up, and I'm going to fly up. You can see, as I
start flying up, the atmosphere actually
starts to thin automatically. It's thinning. It is darkening. This is kind of
a plane altitude. Keep going up. You eventually
automatically go into space. This is amazing to see. You can see, in fact, if I
start going up all the way, we've left the planet. We're now in space. The atmosphere is
a sphere, and if we were to rotate the
sun while in space, you get some really
nice shading and effects that just automatically appear
on the surface of the planet and on the atmosphere
that surrounds the planet. In fact, I'm going to
position the twilight zone over our playable area. Now we basically have this. You can see it's
pitch black here. It's night over here. This is morning or sunset,
whatever you want to call it. This is twilight zone. And if you start going
back into the surface here, into the area, you'll
get this really nice blending of light. This is amazing to
play around with. A couple of other cool
things about this. As you fly away--
and again, you might need some very large numbers. I'm going to bump
it up a bit more. I'm going to move the
sun a little bit again. There is an option here
called Transform Mode. By default, that is simply
set at World Origin. But if you set it at Planet
Top at Component Transform, you can move the
whole atmosphere. That's a cool thing. There's another very
cool thing, is the fact that by having a setup like
this, where you essentially actually have space
surrounding an actual planet with an actual
atmosphere, it means that if you were to
want to simulate a moon, you can do so by placing
an actual, full-sized moon into the environment. Over here, I've made
a simple Blueprint that holds two giant meshes. So you can see there's
nothing in here. It simply creates a
material instance. If you look in the viewport--
and it might be a little bit difficult to see
in here, but we've got two gigantic meshes,
a moon of a moon, and the main moon itself. But that's basically it. If you place that into
your world, placing it and put it to 0, 0, 0, just
for artistic purposes-- and what we've got now is we've
got an actual moon in here. This is an actual 3D mesh. You can fly to it. In fact, you might
need even more speeds. And we're talking about millions
and millions of units here. And it's, again,
amazing to see, I think, that the engine is handling
this so well, even though you're at massive scales. So we've flown to
the actual moon. If you look at the
surface of the planet, you can see that moon from
the surface of the planet. It's a bit low in
altitude, so I'm going to raise the
altitude a little bit just for the sake of
getting it to appear. And you can see we are dealing
with immensely large numbers here. So I have 20 billion, or
whatever I just entered. The moon shows up and
blends with the atmosphere automatically. If it gets evening, you
actually get a half moon. You can get a full
moon, depending on where the sun is on the
other side of the planet in the middle of the night. All of this is just really,
really awesome to see. So that's one way you
can approach moons with this system. Now, a few things more
before we move on from there. There's a couple of CVars here. In fact, there is a wide number
of CVars available, around 20, 30 or so at the current count. Later on in this
presentation, I'm going to show you which ones
I'm using in this presentation. But just to highlight the
most important ones before we get to that point, FastSkyLUT
and FastApplyOnOpaque. I have turned both of them off. By default, they're
enabled, and they're enabled for the sake of performance. If you disable it, you lose
a little bit of performance. It does seem
perfectly reasonable. But you get higher quality. And in particular, when you
need a transition from ground to space, you might notice
with the default settings that you get a slight bump. There's a slight hitch at
some point where it switches from ground view to space view. If you disable these
two, you're going to get it completely smooth,
like I just had in my presentation. There's a few other
things there, too. SampleCountMax in particular. This is going to be
very difficult to show on the video due
to the compression, but you can try this at home. SampleCountMax is
essentially the quality of the atmosphere rendering. If you bring this down to
8 or 16 and go into space, you're going to see a dotted
structure on the atmosphere. It's noisy. If you make it 64, it's
going to be smoother. Moving on to
material integration. Here's another really
cool thing, I think. Because the feature, as it
is, it's really, really cool. But you might get
to a point where you want to customize further. Let's say you want to do clouds. Let's say that for
some artistic purpose, you want to do something
special with this sky that goes beyond the gradient
that it generates by itself. Let's say you want
to go further. You can do that, because
the Material Editor is able to intercept
the rendering and work with the information
that the sky renders. In fact, I have a very,
very basic sky sphere here. I'm going to place
it as an example, and make a very basic
example out of it. Position the camera back
at some central place. Here's the sky sphere. Again, a very basic mesh. And I have a basic material,
which is my basic sky material. Drag that on top, and what
we're getting now is this. Now, the material
is not finished, so it's currently black. Go into the Material Editor and
take a look at what we have. There is a number
of nodes that are exposed in the Material Editor. So the Sky and Atmosphere
Aerial Perspective, Distant Light
Scatter, Luminance, a couple of these
other ones, right? Several of these
are more optional. This Atmosphere
Aerial Perspective is the sun's wide
glow and tint. So essentially, the
wider glow of light that comes from
the sun in the sky. Distant Light
Scattered Luminance is the atmosphere
ambient light or ambient tint, which is really
useful for a few things. We'll get back to it in a bit. Light Direction is the actual
angle of the Directional Light. Also really useful. I'll show you a few
tricks with that in a bit. And then Light Disk
Luminance is the sun itself, so just the circle
that makes up the sun. Light Illuminance is the
atmosphere intensity color of the sunlight
hitting the atmosphere. So the way the light actually
hits the atmosphere itself. And then Sky Atmosphere
View Luminance is the gradient as you see it. So essentially, this
one and this one is what we're seeing by
default. In other words, if I were to connect just
this one to emissive, and it has to be
set-- by the way, the material has been
set Shading Model Unlit, which is a requirement. And there is a property
in here that says, Is Sky? And we've said yes, it is a sky. Right. So just applying this and taking
a look at the sky, we have-- we're now getting the
same gradient rendering on our sphere. If you were to make the sphere
larger than the small one, we would get this. You can see it cuts
up from the world. If you go through the sphere,
we see the rest of the world, right? So it's the same way we've made
skies in Unreal for many years, but now using this system. Now, if you add these together,
if you add to the Light Disk Luminance and View
Luminance together, you're getting what
you had before. So this is the most
simple setup that mimics exactly what you had before. You can see, the sun is there
and you have the gradients. It's real-time. Everything's exactly the same,
except it now renders a sphere. But you can go further with
that, which is interesting. So for example, you could
do clouds with this system. I have a very basic set-up
here, but it shows a potential. I have a simple cloud texture. It's panning a little bit. It's a little bit scaled. It uses the Distant
Light Scattered Luminance to apply the ambient color of
the atmosphere to the clouds, so that the clouds
aren't full bright, but the clouds are actually
adjusting their color to the current ambient tint,
making a little bit brighter. And I'm going to
add that together with what I already had. And that becomes emissive color. Having done that,
we get some very basic clouds. And again, the sky
is a bit small scale, so it looks a bit weird. But as you can
see, in the sunset, the cloud colors nicely
blend in with that. So you get basic clouds. If you make a more complex
set-up out of this, this is one way you
could do clouds. That being said, there
is a different way. So I'm going to
delete that again. Close material. I'll show you an alternative. This is another
approach I've trialed. I've made a basic Blueprint
here called Cloud Layer, but the only reason
it's a Blueprint is just to make it easy for
me to place during this video. Within that Blueprint,
there is nothing there. It's completely empty. There is just a
Static Mesh there, and the Static Mesh is a
very, very, very large plane. In fact, the plane is as
big as the entire surface area of the entire planet. That has a material applied,
which is this material. And this is now my
cloud rendering. And I'm using very much
sort of the same system, so I'm blending in all kinds
of different cloud textures. And we're blending
that with a couple of different other things. When you go into
space, it gets brighter on the edges with Fresnel
and that kind of thing. But at the end of the day,
I'm using the sky atmosphere information in the material. It's the same thing, except
for what I've done differently, is that in the properties,
it is set to translucent, and I actually
haven't used a sky. And by having done
that, this allows me-- as an alternative
way forward, this allows me to have a translucent
layer that literally goes around the entire planet. You can see, there is
a cloud layer here, a very high-altitude,
thin cloud. That is a large,
planet-surrounding translucent layer. In fact, if you
go into space you see those clouds
surrounding the planet, and they blend with
the light as well. So that is an alternative
way of doing this. And then you have the moons
rendering behind the clouds as well by doing it like that. Now, this entire material
integration that you have here has other purposes as well. There's all kinds of
things you can do with it. One of the things, for
example, I have over here is a simple example, too. But I have some smoke drifting
through the whole world. That's the Niagara
particle system. That's not that important. What is important
is the material that is attached to it, because
that material is also reading into some of this information. So the important one
is Light Direction. Light Direction
tells you the angle the sunlight of the Directional
Light in the material. If you know the angle,
you know when it is night. In other words, your
materials can understand when it becomes night. You can have headlights
of vehicles automatically turn on the moment you rotate
the sun away with Control-L. You can have lights in
vehicles and buildings and everywhere else
automatically turn on. You can have particles
like the cloud particle automatically
increase or decrease in brightness as soon as it
gets night or certain conditions are met. So some really cool
things you can do with it. You can use it to blend things
better into the atmosphere by reading that information. Next up, we're going to take a
look at a couple of random tips and tricks and CVars as well
as the stars, an approach to how to do stars. First of all, Heightfog. So if you had the normal
Exponential Heightfog-- and just for information,
the original Atmospheric Fog is not compatible together with
the new sky and atmosphere. But the Exponential
Heightfog is. So if you were to
drag that in-- so I'm going to combine the
two, and this gives you some additional control
over the fog because you need more density or up close
or in valleys or anything like that. So I've dragged
it into the world. Now, by default-- in
fact, I can show you that by putting the height
fall-off a bit more extreme. So now we have very,
very dense fog. But in the valley
over here, by default, that will not respect
the sky and atmosphere and the updating of the sun. So a few things that
you would have to do. First of all, in the
project settings, you would have to enable Support
Sky and Atmosphere Affecting Heightfog. So I have that enabled. Simply look for height, or
one of the other keywords, and enable that. And once you've done that,
also important is the coloring is actually additive. So fog in scattering color
and directional in scattering color, they're additive. So you're supposed
to make them black. And if you've done
that, then it will now respect, automatically,
the same blending of colors and everything else
and update along with the sky. We'll fly into the fog
over here so you can see. Again, some really nice
pictures you can make with that. Really nice atmospheres you
can make with all this stuff. And these kind of-- nice, the
silhouettes of the trees here. Some-- it's just-- it's just
awesome to play around with. I'm going to set the density
to a much, much lower value for a second. Here we are. You can also drive
this through Blueprint. You can do this the usual way
by simply scripting anything you wish into it, right? So you do something on
tick, for example, in the Level Blueprint or
in an actor, or you could say on tick, update the sky and
atmosphere Rayleigh scattering, when it gets evening, or
when a storm comes in, or anything like that. You can do that on the fly. In my case, this one's a
little bit more challenging, because I wanted to make sure
that everything works entirely and only in the viewport. That was a bit more
of a challenge. To facilitate that
further, we've made a change that's
going to come in 4.26 that will allow you to use a
construction script when you're using Control-L.
Right now, in 4.25, that is not yet supported. So what I've done
now is I'm going to delete the Directional
Light I placed a while ago, and I'm going to place
a Blueprint Directional Light instead. Here we are. And so now everything looks the
same, works again the same way. But if you look at what
I've done in that Blueprint, I have a bit of
functionality in here. So you're welcome to
script any of this similar to what I've done. Because of this, I now have
support for an eclipse. You can see the moons
are also rotating around. And if ever I can get
the sun to show up behind the moon,
which is a little bit difficult at the moment. I'm going to reset the position
of the moon, which I've previously increased too much. Let me do it like this. I actually have
support for an eclipse. It darkens, and the
sun comes out again. There's a bit of flickering
from the Control-L previewing, but it works. And all of that is just
done through Blueprint. Now, as mentioned, this is
running on construction script. In 4.25, the construction
script does not update when you lose Control-L.
In 4.26, it will, and therefore it will enable this use here. If, meanwhile, you want to do
something like this in 4.25, my work around before has been
to build a Blueprint widget, and in the Blueprint
widget, you can do things per tick, even in the editor. So I have the same
set up over here, and that has the same result. Another important CVar here is
MultiScatteringLUT HighQuality. You can enable that it. Will give you a higher-quality
multiscattering. And it will be noticeable both
in space and on the surface of the planet. You will get a nicer
scattering of light. There's also a way
of doing stars. This is a little bit of
an experimental approach I've taken here, but I'd just
like to share what I've done. I have a post process
material in here. So there's a post
process volume that has a blendable, post
process blendables, which is this one over here. And if I enable that,
this is currently disabled for the sake of the
video, and it becomes night, you get stars blending in. Stars rotate around
with the sun to simulate the orbit of the planet. But it actually nicely blends
with the atmosphere, OK? Including if you go into space,
I've got stars here, too. The way I've done
this-- and again, it is a bit of a weird
work-around, I would say, but it is a post
process blendable here that blends a cube map of stars
into the furthest-away pixels. So you've seen that I only
take the furthest-away pixels. I do a couple of
additional checks. I check it the camera
is in space or not. Then it behaves differently. And I check how
bright the sky itself is if you're on the
surface of the planet. And I fade in the stars
only in those spots where the sky is dark enough. So not where the sun
is located, and more like on the other side of
the horizon during sunset. And that becomes my set-up
here to blend in stars in a way that I can go from the
surface of the planet into space and back and
have that work seamlessly. So that's one approach you
can take there as well. There is a thing that's been
an Unreal for a long time. It's the ability to capture
the updated skylight. So that has been in the
Engine for a long time, but it's always been a bit slow. It's been heavy on performance. So up until 4.25-- until 4.26, rather. 4.25 is going to be the last
version that has it like that. A few words here on the
updating of a skylight. Now, until 4.26, so
before Unreal Engine 4.26, so as it is currently,
at the time of recording of this video, in 4.25,
the way, and the only way, you could capture and
update the skylight would be to use the Blueprint,
the appropriate Blueprint node, that would do exactly that. Here's an example of that. This is currently
stopping it, because I don't need it in this version. But I had a delay in there. Every half a second, it
would do Recapture Sky on the skylight. That was the only way. That was pretty
heavy on performance. You would notice a noticeable
hitch in performance every time that would trigger. It would be significant. So in 4.26, and
moving forward, we've added a new option on
the skylight itself that is called
real-time capture. If you enable
real-time capture, it will do exactly as
the name implies. It's completely smooth and
completely in real-time. And it costs very, very
little performance. I'm using a 32 cube
map resolution here to further reduce the
performance impact. On a Playstation 4,
this is currently taking 1.4 millisecond
for a 128 cube map, so the performance cost
is perfectly reasonable. And that's a really nice feature
that's coming in the future. It's simply a tick
box, and it works. Now, earlier I
mentioned that I'm using a whole number of
specific settings here. So for reference, these are
the settings that I am using, the different CVars. This is a high-quality setup. It's not necessarily what
you'd use for a game. But so this is the
high-end approach to it, and you're welcome to
experiment with it. A couple of these are specific
to 4.26, like everything, essentially, volumetric cloud
is for the new volumetric cloud system. That is currently
not yet in 4.25. But you're welcome to
experiment with these settings. And I'm going to
wrap up by looking at the new volumetric clouds. So while you can build a cloud
with translucent layer that goes around the entire
planet, or perhaps blending into the sky material,
displacing the sky dome-- that works, but in
4.26, you're going to get this amazing new feature. Again, this is one of
these kind of things where if you're just
playing around with it, it's just utterly amazing
to play around with this. These are volumetric clouds. If I move them,
when the sun moves, I've made it so that also
the clouds are moving. You get this. And it's amazing to play with. In fact, you get
automatic god rays that go through the clouds. You get darkening of the
environment-- not just of the environment locally. It cast an actual shadow on
the entire world with god rays as the clouds are moving by. So the most amazing
stuff to play with. You can go into the clouds,
if you wish, et cetera. Fully 3D. This is being set
up in the same way that you do the current
volumetric rendering. So there is support in the
Unreal Engine for volumetrics. This uses the same system. It uses an actor called
Volumetric Cloud Actor that gets placed in a world. In itself, it
doesn't do too much. There's not too many
settings available. In it is basically the height
of the clouds, the altitude or the clouds. But most of the work will
come down from the material. And so it uses a
volumetric cloud material. And this is the one I've made. This is built in part on top
of Ryan Brucks' initial one, where-- and this is the
core of that material. It uses a volumetric
texture to define the noise of the overall
3D shape of a cloud, and then it blends
various other textures on top, various
ways of panning it, subtracting parts of
the bottom, softening, and a couple of
different setups here. And then this is what
drives the clouds. To recap, in 4.25,
we've added the ability to move the whole atmosphere
when, for example, in space, per pixel atmosphere
transmittance, so you can have atmosphere
shadow on other measures, for example moons. Sun luminance is now
scalable and colorable. You can scale that
via the properties if you need to do so
for artistic purposes. That's going to be 4.26, though. Also in 4.26 is the whole
volumetric cloud rendering. Sky and atmosphere
volumetric shadows, as you've just seen in-- a
couple of minutes ago. Construction script support
for Directional Light using Control-L, and the new
real-time skylight capture and convolution in a
performance-friendly way. That is what's coming up next. So that brings us to the
end of this walkthrough of our new sky and atmosphere
rendering capabilities and features. I hope you enjoyed
it, and thank you.
It's very impressive what they have achieved opening up so many possibilities for even smaller developers. The future is very bright. :)
This looks fantastic! I’ve wanted something like this for ages. Unreal 4’s sky system was always really basic.
Geez, it’s not gonna be long until the one thing that Star Citizen constantly touts is gonna be free and available to literally anyone with a copy of Unreal Engine and a decent PC, huh?