This video is sponsored by Skillshare. Hey, everyone. It's great to see you again. It's been a while since my last
video, but it's good to be back. I hope you had a great summer. Now. The topic of today's video is
going to be all about the new and improved path tracer in. Four point 27 that just
released not too long ago. Now, previously the Patriots
are had a number of limitation. It was much slower and it didn't
support the vast majority of material type like subsurface, scattering,
translucency skies, so on and so forth. Now, although features are
mostly supported and it's amazing pass rates are rendered what
we call a ground truth image. So this is similar to offline
render Ruth like V-Ray and Arnold. It works by casting lots of rays into
our scene together information about light and color to shade, a given pixel. It includes feature, complete materials
within reflections and refractions, super sampled anti-aliasing and
approximate of caustics, which is totally new, but why he was at at all. What's the point it's slow. It's not real time. It kind of defeat the
purpose of using unreal. The path tracer is extremely useful. When you want to compare your real
time lighting with a fully path rate renderer pass tracer don't lie. They're not approximation
of what light should do. They are physically accurate
giving you much, much better result, much better shadows. So much more detail. You can then use this to measure the
quality of your real time rendering and make adjustments from there. So for me, coming from a VFX background,
Beyond excited to start working with the path tracer again, I think this is
an addition that makes unreal insanely powerful, but you might be wondering,
well, what's this path tracing thing. And video had been trying to sell
us on the RTX and Ray tracing stuff. What's the difference. They are more or less completely
interchangeable terms we could nit pick about how Ray tracing is a bit more of a
general term at the poet, the passenger. But outside the people writing
render engines, I doubt that definition difference matters. So in order to enable it and get
it running your engine, you need to make sure that you have Ray
tracing enabled in your project. This is a must, there's no way around it. So in order to enable Rachel thing
on our project, we need to click on the settings button up top. Then click on project settings,
and you're going to scroll down to the side where it says platforms,
windows, click on the window button and where it says default RHI. We need to make sure that this is
set to direct X 12 and the next step and the search detailed panel up top. We can click here and type Ray
tracing and you'll need to make sure that Ray tracing is turned on. Now, when you click on this here, a
window will pop up, asking you to enable the support compute skin cash options. Click. Yes, you're going to need this as well. Once that's done, you can restart
the engine and you'll be ready to go. Now we're ready to jump into how to use
the path tracer and all of its settings. So now the best part about
the path tracer is you can. Turn it on without having to do
anything else in your scene, you don't need to change your materials. You don't need to do anything else
to what we're going to do is we're going to go to the button up top here
and switch just to pet tray thing. Now be careful things are going
to slow down considerably and this video will actually get
pretty choppy when I click it. So I'm going to turn this on right here. And you'll notice that it's
now starting to do its thing. It's slowly calculating our samples. Our image is getting progressively
better and better, but now you might realize that's just one frame. If I turn the camera rotate around, you'll
see, oh, this does not look so good. This is really slow. Especially if you're used to,
you know, working in real time, this is a real pain to work with. So all of our path tracing
settings are controlled through post process volume right here. And in the detailed panel, we're going
to search for path and you'll see right here, we have samples per pixel, 16,384. For the sake of the video, I'm
going to turn this back down to 10. And because we have the de-noise or
enabled right down here, pay attention to what happens when I hit enter. Now, poof, everything is back to normal. Everything kind of
de-noise now what happened? Why is it so fast now? Why is it such a clean image? That's because as soon as the 10 samples
here have finished calculating the de-noise where it's going to kick in,
whereas previously it had to finish the 16,384 samples before being de-noise. That's a lot of samples. It's going to take a very long time. So for previewing purposes, it's often
easiest to just tone down your sample counts so that you can get it easier,
quicker, faster, better preview. But now we have a series of things that
are just plain wrong with our scene here. The first of which being our image
is very splotchy is kind of ma like we, we've lost a lot of fine detail,
especially on the wood floor here. If I switch this back to. Okay. Notice how we had a whole
bunch of like gritty texture. Like if we have a lot of grime, there,
there was lots and lots of details. But switching to the path, tracer,
everything is kind of mushy. It's kind of muddy. What's happening. That's because of the denoiser, the
denoiser is incredibly aggressive. And honestly, if you want the
absolute Crispus sharpest best possible result with the past tracer. You're going to need more samples. There's really no way around that. You're not going to be able to get
the Crispus best possible render with low samples and a Detroiter. Now, there is a very useful console
command that you can use to give you a progress bar of the rendering process. So opening up the console command menu
at the bottom, I'm going to enter our dot path tracing dot progress and display one. And by hitting enter. Now when I moved to camera and you'll
see, we have a progress bar at the bottom. This is super useful for just getting
an idea how much longer you need to wait before the render is complete. If I create the sample up to 500, now
the progress is going much slower, but it's really nice to know how
much longer do I really need to ways. So jumping into Photoshop real
quick, we have two renders here. So one would rendered with 10 samples. Plus the Dean razor and the other one on
the right hand side here, what rendered with 500 samples with the Dino laser. So at first glance, especially on
a compressed video on YouTube, they may actually look pretty identical. You might not be able to tell them
apart, but the moment you start zooming. You'll notice that the version with 10
samples really starts falling apart. So right here on the base plate, the
kind of black plastic thing here, I had a roughness texture with a bit
of roughness breakup in there, and you can see it here on the 500 sample
version of the render, whereas in a 10 sample version of the render, the
de-noise are completely obliterated. All of that detail, there just,
everything is perfectly smooth here. There is no back breakup, same
thing for some of the details on the shell of our turtle here. So paying attention to the scale
detail on the shoulder versus here and on the top of the head. We have a lot of scale detail there
there's lots of little nitty gritty stuff. Same thing was the edge
of the shell right here. Whereas on the 10 sample version of the
render, all of these details on the top of the head and on the shell, it's been
completely destroyed by the de-noise or because the de-noise is so aggressive. We can even see on the
front of the shell here. We got to kind of not cheer
a bit of damage on the shell and here it's barely visible. Let's go ahead and zoom
in on the floor here. And the same thing kind of applies. It's actually surprising how
well the de-noise are worked, but it's no comparison to the
500 sample version right here. We get so much. Crisp little details. It's the small details like this
that make a substantial difference in a quality of a render. And the same thing applies with just
the edge of the wood plank here. We got these little notches, the
ever so subtle break up of the lines. Whereas here it's just kind of smushed. We've lost a lot of detail here. So again, it's pretty subtle and
I'm actually quite impressed with the performance of the Dene Windsor,
especially at higher resolution. But if you want the best possible
quality, there is really no way around using more samples. In fact, if you have enough samples, you
may be able to omit the de-noise or, and. So it's worth keeping in mind that
the de-noise or really is mainly intended for use with still images. And you can see here, I have a render
with 100 spatial samples with the de-noise or turned on, and you'll
notice that right around here or really all across the entire image it's
getting really flickery and jittery. And it looks like crap. The reason for this is because
the de-noise is not temporal. And what I mean by this is
the denoiser, or does not. De-noise the current frame basically. The Dino is of the previous frame. So each frame will be deemed noised
in its own way, individually resulting in a super jittery mess like this. Now this can be mitigated somewhat
by either having more samples. Adding in, from temporal samples in
the mix in the movie render queue. So now you can see right here, the
results are much better with temporal samples, but I've increased the
contrast here so that we can see more. Clearly, we still get quite a little bit
of jitteriness and flickering ness in the shadowy areas, especially areas with lots
of details, right around the head here and in the area that have lots of lenses. So just keep in mind that the de
noiser does not necessarily work all that well with animated footage. Now, next up in a detailed
panel, we also have max bounces. Now the amount of bounces you have here
will also affect your render times. So toning down my sample. So let's say 106. And turning my back bounces to one. You'll notice that we start getting
a lot less indirect lighting. So what's happening is the light comes
in, hits our surface and bounces one time. If I do three bounces, you'll notice we
get a bit more indirect lighting, right? Especially our box right here. The box in the bottom left hand
corner is a great indicator of what's actually happening here. So by setting this down to one
again, You'll notice our box in the foreground is very dark. Cranking this up to 10. Now in the darker areas, things start
getting lit up a little bit more. There comes a point of diminishing return
when it comes to the amount of bounces. So you don't need to have
an insane amount of bounces. In fact, for many
renders, I've captured it. Really, you should only be using as
many bounces as you need, but we'll get a little bit more into that later when
we touch base on the glass materials. Next up we have filter width here,
which says the anti-aliasing filter. So lower values will be a sharper
and more aliased whereas larger values are softer and blurrier. So it's switching over to
another environment here. I just want to show you a few
other nifty features that we can find in the past rating settings. So I'm going to go ahead and delete
every single light in my scene here. So delete this directional light. And in my eighth year, I backdrop,
I'm going to make sure to my skylight, it actually disabled. It's not affecting our world. Right. So we have no license. Our scene. The only thing in our teen will
be this emissive HTRI texture. So what you'll see,
everything is pitch dark. And when I turn on the path tracer,
you'll see, boom, we've got light. And the reason for that is because in
the post-process volume, if we search for path trading, We have emissive materials. Okay. So everything that is
emissive will cast light. If I turn this off here. Well, there is no more light in nursing. Nothing is happening. So this is the really nifty feature. This is super handy when
you just want to throw in. Yeah. Nice looking HTRI you don't need to
configure any skylight or anything. Everything just works kind of the
way you would expect again, because of the de-noise or you'll see,
everything is kind of splotchy. Doesn't look that good. So again, you need more samples
if you want some CRISPR results. And now if I want to throw a
directional light in here, well I could, and now we have a much brighter. So in this section, I wanted to
talk to you a little bit about changes to the way that materials
are handled with the path tracer. And we're going to take it. I look at some of these right here. So first off you've got the thin
translucent model right here, which is kind of like a clear
plastic type of thing, but also cast colored shadows right here. Next up we have proper path traits,
glass, which looks phenomenal. And looking at the example here,
we now have approximate caustic, refractions, and reflections,
which is just so nice to have. Now next up, we have frosted
glass, which is the same material as the regular glass material. However, by upping the roughly. Of our glass material. We can now have frosted glass. And lastly, right here, we have random
walk subsurface scattering in 4 26. The pass rates are, did not
support subsurface scattering. So this is a really,
really nice addition to it. In our project. So let's take a look at these
materials one by one, just so that you know how they are set up. So starting off with the subsurface
scattering, the path tracer now uses a random walk, subsurface scattering
method, which all happens under the hood. You don't need to enable any plugins
or any settings to get random walk, subsurface, scattering to work. It just does right away. So all I have here is the shading model
at the bottom here, set to subsurface. And with these four nodes, I can
control the color and how far the light will scatter through my model. Next up, let's take a look
at the glass material. You'll see here. It's nothing complicated. We only have a flat base color,
roughness, opacity, and the index of refraction of 1.5 with a blend mode
set the translucent here and the lighting mode set the surface forwards. That's it. That's all you need to do in order
to get really good looking path, trays, glass now, and independent. You want the frosted glass? All you need to do is to increase
the roughness of your glass material. If you want to know more about Rachel H. Glass specifically, you can watch
my tutorial on it right here. The link of which will be down below. Now, the last one I want to talk about
is the thin translucent method right here, and the material set up for this. It's a little bit weird. It's a little bit
different than the others. So let's take a look at it right here. Again, the material is pretty subtle. Make sure that we have our blend mode
set, the translucent and the shading model set the thin translucent right here. Really? The refraction, no Palestinian
roughness settings are all identical to the glass material. The only difference here is you need to
add the thin translucent material node right here by pressing the tab button
search for it, thin translucent material output, and you'll find it right. And the color right here is what's
going to determine the color of your shadow, the color of your actual
plastic, or then translucent material. So this is perfect for like
plastic wrap or anything. That's very thin like a bubble. I don't recommend that you use
this, add the colored glass option. It is not going to look very good. It's going to look more like plastic
than glass, even though those material types are relatively similar. They are different. And if you're looking for the absolute,
most physically accurate result, you're going to need to differentiate those two. So when working with glass materials,
it is very important that you have enough bounces to work with. So let me demonstrate right here by
selecting our post-process volume and going into detailed panel, we're
going to search for path tracing and let's demonstrate what happened. When I turned down the max bounces
to something like one you'll notice none of our glass material. Are really looking like laugh anymore. If I set it to two. Okay. It's starting to look a little bit better. Three a little bit better, and let's say
10 now with 10, they look as they should. So again, when using translucent
materials, you need to have enough bounces for them to render correctly. I think I want to talk about in
this section is a few changes to the way that the skylight is
handled with the path tracer. So. The pass rates are, does not support
atmospheric sky or volume metric clouds. So if you have a volume metric cloud sky
set up like this, the one that has like really nice sunsets and such you'll notice
when we go to the pass rates are here. So sky goes completely black. You're not going to get anything,
but there is a workaround. So by selecting our skylight in our
scene, if you set it to real-time capture like that, It will capture our sky. So you'll notice it's a little bit blurry. It's a little bit pixelated and
low Rez, but if we go back to lit mode, you'll see, it is pretty much
the exact same result as our sky. So it is capturing our sky and
creating a cube map for us. So going back to the past rates
were here, even though it's low resolution, we can fix that. So select your skylight again. And in the detailed panel, we're
going to set the cube map resolution right here to let's say 10, 20 feet. And now we have a super high resolution
sky, which is almost the same as the sky that we have in lit mode. Not quite the same, but almost, and this
should be good enough for most use cases. Now, in the event that you don't want
to use a sky system and unreal, but you would rather use an HDI or something. Then the best way to do that would
be to use the HTRI backdrops. You can find right here, if you don't
see it in the list here, you may need to enable the plugin for the HTRI backdrop. Before I put in my Easter, I backdrop,
I'm going to delete my sky system here. Okay. And I'm going to drag and drop the
HTRI backdrop into my scene in the HTRI backdrop in a detailed panel. Don't forget to select your skylight right
here and disable it because otherwise they're going to get a double lighting. You're going to get the
lighting from the image. This of the HTRI itself and also
delighting of that's a skylight is casting on your scene. So be careful about that. And now our HTRI backdrop, it's going
to be our source of light, and now we can apply whatever HTRI we want
right here in the key of map section. So now if I go back to the path tracing
mode, you'll see everything kind of looks the way that you would think. So those are two ways to work
with either the skylight or an HTRI when using the pass tracer. Alternatively, what you
can do is select your sky. Set the source type to SLS specified QMAP
and choose acute map of your choice and just like that we can load in an HTRI of
our choice very quickly and very easily. You're just not going to have the
HTRI showing up in the background like we had with the HTRI backdrops. While you take the time to
process that information. I want to take a moment to thank
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get a one month free trial at Skillshare so that you can start learning today. And with that being said,
let's get back to rendering. So what's all new, amazing features. There are always a series of caveats and. Limitations and things that don't totally
work perfectly to become the pasture now supports more feature than it. Doesn't support. I'm going to go ahead and tell you about
the feature that it does not support. So we've got hair strands, which are
not supported cascade particle systems, spline meshes decals, which is a real
bummer because I use decals all the time. And so do you probably, but hopefully
that comes in a later version. Next up volumetric fog, exponential
high fog, light functioned hair and single layer, water material types. There is no multi GPU support and
lastly is semi depth of field support. So it's important to keep in mind that
the passenger is only using the regular. Depth of field post-process the depth
of field is not a path traced feature. So just keep that in mind and
you can see right here, there is some kind of jitteriness going
on in the depth of field areas. I am pushing the duct with field,
to its absolute limits here. And while it's not perfect, it's. Pretty good. Like the fact that I can get this kind
of result so quickly is phenomenal. So yeah, I might sound harsh toward
the devs at epic, but hats off to them. The fact that they have
pulled this off is so awesome. So I will include it, the link in the
description below to the full list of supported and unsupported content. You can find it right. Now a few good things that you should
probably know about is that when using really bright materials for
interior renders, you should absolutely keep your albido values below one. So more along the lines of 0.8, you
should not be using a value of one anyway, because there is virtually nothing
in the world that has no Beto of one. Even the purest whitest snow
on a top of the Andes will have an albedo of like zero point. So to keep your render times
lower and get a better result, you should keep your base color or your
albido out a value of 0.8 or lower. It's a double whammy. You're really, it's a win-win. And that brings us to the
next section of this video. How do you have to move your render queue
with the path tracer in order to export? Amazing. So the path tracer now works flawlessly
was the movie render queue, as you saw in the intro of the video. So I'm going to show you how to set it up. Now, if you're not familiar with how
to use the movie render queue, you can find a tutorial on it right here,
and you can find the link down below. So let's open our movie render queue
settings by clicking right here and let's click on our settings. It is really important to know
that when comes the time to render within movie render. You're not going to control the samples
through the post-process volume. That is the key takeaway here. So by going to the settings tab here and
adding the antialiasing tab, the samples of your path tracer are controlled through
the spacial sample count right here. If I wanted to have, let's say 500
samples, you need to enter 500. Right here. You should also override the anti-aliasing
and set it to none for better results. But you're also going to want
to play around with the temporal sample count because temporal
samples will give you a much better motion blur than spatial samples. Now keep in mind that the temporal samples
and the spatial samples kind of work together and they multiply one another. So let's say for example, I wanted
to have five temporal sample counts. You no longer need to have a
spatial simple count of five. You only need 100 because it's going to do
100 times five for a total of 500 samples. If you wanted to have 10 temporal
samples, then you only need to have 50 spatial samples. So what I recommend you to do, if
you start by figuring out how many samples you're really going to need
for your render and then do the math and then figure out how many
spatial and temporal sample counts. That is how it works. And that's really the main takeaway here. And now, lastly, before rendering, you're
going to delete the deferred rendering tab here, and we're going to add. Path tracer. And you can find down
here, you'll see here. The passionates are the exact same
settings as a deferred rendering tab, and that's really all you need to do. So my preferred rendering
settings are as follows. The temporal and spacial sample counts
completely depend on what it is, I'm rendering, but in general, 16 spatial
samples and 16 temporal samples are a really good starting point and last. Turn off that Dean wiser. Yeah. You heard me noise is detail. Every moving to noise means removing
the detail and your results are going to end up like a splotchy myth. Like we've seen it in the
examples throughout this video. So in the example you saw
in the intro, absolutely. No de noising was used and
the result turned out pretty. Okay. In fact, I prefer to de-noise my
rendered in posts that like individual results or something, because I
have way, way more controlled. Once you determine how
many samples you need. And the movie render
queue is set up correctly. Hit that record button. It's a bit of framed out. This video has helped you out. Don't forget to hit the subscribe button. It really makes a big difference. Thanks so much for watching
and we'll see you next time.
