Mtg 24/26: Thu-03-Apr-2025

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Volume Scattering

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Audio Transcript

You like me to ask the question again,
sure,
for the assignments, you have them due on April 8. We were
wondering if you're we'd be willing to extend the deadline
to possibly the 15th, but I thought you mentioned you would
accept them until then, so We're wanting some clarification.
Yes, okay, you
now, assignments you
So the way it's phrased, i
i Sorry I was late today. I was not keeping an eye on The clock.
I
It seems to be struggling to make a connection and
let me try the other part.
I fingers crossed And
okay, so that's, that's, if that's the way it's set up now,
so you can submit to labor 15 with a 20% penalty. I
Who would like to have april 15 with a smaller penalty? I
was wondering if you would be a little bit later on The initial
due
date or 11th last year classes. I
so we did that
you can still have the end cut off be the 15th, just change the
initial duty to be april
11. Will be April 13.
Who likes that idea? Do?
Okay, let me see if I can happen
quickly. Here. I
Okay, so taste that I
Oh, okay, I think I successfully made that change. I
and she got a message about it, yeah, okay,
and the other question we have was content of the final exam.
What is supposed to be the content of it
more so? Is it cumulative? Is it more so focusing on post
midterm, etc?
Yeah. Yes, okay, so I
so as I said, Before I welcome your input, I
and suggestions I
Okay, so that's My advertisement for Your input. I
so after the midterm, I said
that I'm going to ask the same kinds of questions on the final
so if You're familiar with the midterm, that'd be A good you
try it.
So the final will be comprehensive, whole semester,
mid to more Questions And
so
sources We've looked At You
okay, so I'm going to ask you to show that you understand the
concepts involved, rather than, you know how to write it the
integral or something like that. Does that seem okay? Yep.
Will it be like a similar format to the midterm or it's short
term, like short answer your questions.
Will there be any multiple choice questions on there?
Would you like multiple choice questions?
Some would be nice.
They take less time because I ran out of time mostly on the
first victory. Yeah, then again, we'll have more time on
the final
section. There's a good like, say 40% of the exam is multiple
choice. Gives us a little less stress. I
Yeah, so we had some issues getting started on time for the
midterm,
no matter how
I thought I was prepared to deal with The eventualities. Then
they came to bite me.
Anyway, I
it. So if you want a number of multiple choice questions, so
I'll make this a question, the quiz question for you over the
weekend to think up. So what are some good multiple choice
questions for the exam? Do
you want, like the potential answers, or do you want just the
question, like,
when we give you questions suggestions, do you want us to
to give you what we are thinking? The answer should be,
yeah. Well, I think it's especially true For multiple
choice questions that I
it not sure why I stopped.
Oh, that one, yeah,
so how would you like my multiple choice question on the
quiz for today? Oh, yeah. I get
the matching one select for the six drop six possibilities.
Yes, that was
nice. That actually worked, I think well, because then you
actually still have to know which one belongs to which,
yeah, as well as whether it's increasing or decreasing, or
what it's doing that's moving
a little bit there. Oh, there we go.
Okay, yeah, that's cool.
I rendering, or if it was actually a panic,
where did you get your screen saver background
kinds with the operating system? Oh, well,
Daryl, to see what don't
know if there are other ones that are available, but this is,
this is called Sequoia, this release, which is
1015 1015 Yeah, I
1015 Yeah, 15.33
anyway, yeah, I think it was 10 to Mark 15, but it's really not
anymore.
Anyway, i
Does that make sense for the exam? Okay, so
provides the clarity that we needed.
Wow, about the assignments, yeah, a rubric
that the TA uses to grade. Because, like, when we get the
grades back, we get like, 2.7 out of three. Like, that's like
a good instead of an exemplary. But like, I don't know what's
like missing to go from like that good grade to the
exemplary, or is it just kind of arbitrary?
I it's not arbitrary, but
I think we struggle To i
to make them Clear, so much
anxiety. I
I would it would still be helpful for me to fill that in.
I think so, okay, we'll work
on it. I want to say here, so
the way that I put this together was
the comment would be the same for exemplary plus exemplary and
exemplary minus. It's
just like a near miss and above and beyond or what.
Yeah, so
the issue is trying to differentiate
those three levels of each each
section that's understandable,
so exemplary, plus that's full marks and and then it goes so
it's multiplied the way the
points available for the category times 1.0 for that one,
and then it's point nine, point 8.7, and it goes down to point
one. So if you, if you submitted something, you'll get a 10th of
the marks anyway.
It should have explained this before.
So the idea, though, is that not everybody's going to get an
exemplary plus or
not, everyone should expect to get an exemplary plus. I
think he was more wondering, how does he get feedback on what he
did to find out how he could improve to get a better chance
of having an exemplary closed, basically a worded rubric, like
a worded rubric where you need to do this or you're missing
this.
Yeah, okay, successfully having the tetrahedra is worth this?
Like, that's like the requirement to get here, doing
the proper texturing of the desk is enough for this. It gives you
a little bit more guidance and direction, what specifically
you're looking for, so we could be more on the mark.
Just something to think about, I suppose, first teacher, it would
help a bit for like, what specifically, specifically
you're asking for, as opposed to, like the general, yeah.
Okay, so do you want to talk about, do you want to talk with
me about the feedback you got from the first assignment.
Yes, I still have office hours, although no one comes to see me.
No, that's right, you do. You're the exception that proves the
rule. Anyway. You can do that, and we can talk about things
more and more specifically. And I will if
so the comments I've written in the past in the rubric are maybe
a little more general than the specifics that we just you just
suggested. Yeah, okay,
there's got to be a healthy balance between the two words.
The grading is general, but it's more the feedback that we're
looking for, some more specifics on, not necessarily the general
like, the general grading, like, Okay, I know what I mark. I try
to tell people, Hey, this is why you lost the parks, or this is
what you were missing. So I think it's more that aspect that
we're looking for of, okay, we've lost the marks. Okay, fair
enough. You've broken it down into which parts like the Create
scene, all that stuff. But when we don't get that exemplary,
plus having an ID, getting more specifics on our particular case
as to why we're not getting that okay. How could we have taken it
to that next step?
Okay, does that make sense? Yes, it does. So I that's an easier
fix to get some more comments from the marker.
Am I wrong? Is that kind of like for the
document, the run parts like, where the Analyze? Parts like,
what more analysis? The Green Scene is kind of understandable.
Like, yeah, I made a pretty simple scene I didn't really
like that's way too much for increasing way more extra
objects than the virus that would kind of makes more sense.
Why? How could it document better? How could I analyze it?
Okay,
all right, so
I'll get some more clarity about that for you about the what was
done, and then what will what we'll use for the assignments
that are coming up. Still, I
thank you. You're welcome.
Okay, So our quiz for Today, we're
so what's what accounts for The increase in radiance along
array? Do?
Okay, so The reduction,
the reduction
in radians, radiance
due to the conversion of light to another form of energy,
okay, emission
radiance that's added to The environment. It's like the
bottom one, last one.
Scattering is radiance heading in one direction that is
scattered to another other directions.
I that's number two.
Declares the particles. Yeah, so I
now is it generally accurate to say that radiance is constant
along rays between surfaces, no
in a vacuum, and since most places are in a vacuum, it must
be true. That's the assumption that all spaces are vacuum.
Let's change.
Then again, there's also radiation in The vacuum. So it's
like I
the answer not saved number one,
got two out of three because you didn't answer the third
I didn't answer the first one. Yeah.
Okay, so we did pretty well with that one. I
Yeah. So we're not always working in a vacuum.
Like, generally, like 90% of the universe is a vacuum. I think
you've got backwards. 99%
universal isn't in a vacuum.
Mostly speaks about
you big part of the universe.
We're talking Earth, okay, that's
interesting. Cary centric,
Earth. Is there vacuum?
Watching Earth atmosphere? I
so if we have
some null scattering in him and homogeneous. That's
where it varies throughout space.
The degree of scattering will change depending on where in
the material or space.
So we can make it homogeneous by adding I
which makes it easier to sample and
I didn't, this is a five o'clock this is a five minute video. And
I, I and I start to look at but think this is from Unreal
Engine. I
Hey, Lewis, as I said to you, the Twitter D is Henning
Greenstein phase function, you receive this light vector. It
can be your sun, can be your moonlight, and, yeah,
anisotropy, Will you act as the how much amount around the faux
supply you want this value to be distributed in a circular way
from the light vector source. What this means? It means that
this this position here for your light vector, you will be taking
into account. And if we look at inside this, this function, it
is quite simple. It's really math, okay, and you see that,
basically, you take your value for an isotropy. And we you
draw, you see that you have pi here, draw like a mask, circular
mask around the focus, or the origin of your of your light
source. And to make it even easier, I will show how I'm
using here. So this is the pure light vector and an isotropic
value here, and I multiply by this alpha, this alpha from
these material parameter collection I'm using as a
intensity for my sunlight. And you see that is also I use the
same, the same function here for the the moonlight. Okay, so this
is the intensity, and this is the color teaching the end. I am
multiplying here, so I have my color, I have my intensity, and
I'm multiplying and giving this color to something as my
material is a ray Martian material. And like here of
drawing each point, then you can see, this is my skin, which I
use Ray Marsh, and this is my moonlight. Here you have just a
texture with a light behind it. And the intensity for the white
in this is given by another value, but the that material
parameter collection, it is represented here. So as it
scholars in RGB, and the alpha is the intensity. So if I
increase this intensity, you see the effect. Okay. Now look at
this. It is brighter around the source than it is far from the
source. And it is given here like, if I use like, point minus
point three, you see that running lighter. Even
if I look here back, you see that it's darker. The effect
also contributes to the color here. So anisotropic minus point
nine, you hear very strong light and you see that basically far
away is completely dark. And if I just use like minus one,
you'll be completely black because we are like, constant
effect work. One seems to be no effect at all.
Point two,
you see that we have the light totally distributed, because,
again, it is a circle,
so the intensity
and the light color is spread everywhere around the surface,
like a halo shape,
point one,
zero, minus one, you see that is Getting the effect is coming
closer to the center.
And like minus six, it is the most expected for a behavior for
moonlight, of course, sunlight, you can't use this much, so
that's two exaggerated for minus one. So rated four, minus one,
seven I could use building use at smaller steps here. I guess
this explains, well how the function works. See, you go
back so too long a video site. Anyway,
it's a pretty cool use case. Yep, yeah, because if you have
that moon phases and say again like that, then you can have it
so that the degree of light changes based off the moon
phase. You have it sort of automated, to a degree
full moon, as opposed to Crescent Moon, etc. You
so this was
I linked to the set of slides last
week when I didn't have a meeting. But here's a video of
his presentation of the slide. So I thought maybe that would be
a useful thing to look at. It's about bit longer than the time
we have left, but we can watch till our class ends, and if we
have
questions, you can ask.
So first of all, it pleasure, once again, to welcome natty
Hoffman, the natty first organizers course in 2010 as
we're really, always, really grateful to him for always
helping us out find speakers each year.
So nothing is the vice president technology at 2k So previously,
has employed an Activision working on graphics R and D for
various titles, including the Call of Duty series, Santa Sony
a Santa Monica studio, so coding graphics technology for god of
war three, Naughty Dog, and developing first PS three, first
party libraries, westward studios, leading graphics
development on Earth and beyond, and internal driving Pentium
pipeline modifications and assisting the SSE instruction
set definitions we've got along in the last few years history.
Thanks for Matty. Thanks for the introduction.
Hi. So some of you may have seen this background talk before.
I've done quite a few modifications to this here, so
we won't all be all packed so, but one thing that hasn't
changed is that over the next 15 minutes, I'll be going from
physics underlying shading to the math used to describe it. So
what is light? From physics standpoint, it's technically an
electromagnetic transverse wave, which sounds very fancy, but it
actually means that the electromagnetic field wiggles
sideways as the energy propagates forward. This
wiggling in the electromagnetic field can be seen as two couple
fields, electric and magnetic, wiggling at 90 degrees to each
other. Electromagnetic waves can be characterized by frequency,
the number of wiggles they do in a second or wavelength, the
distance between two wave peaks. Now engineers have in various
disciplines have to deal with electromagnetic wavelengths
ranging from gamma waves that have wavelengths of less than
100 than a nanometer, to extreme low frequency radio waves, that
those waves are 10s of 1000s of kilometers long and everything
in between, but the range that we can actually see with our
eyes is both a tiny, tiny subset of that range only from 400 to
nanometers for pipeline to 700 nanometers for red light. Now to
give you a bit of intuition for what 400 to 700 nanometers
actually is, because the physical size of this will
become irrelevant later in the talk. So on the left, you can
see visible light wavelengths relative to this sort of gray
cylinder. That's a single strand of spider silk, which is one
micron in width. And on the right, to give some extra
context, you see that same strand of spider silk, how it
can be relative to the width of human hair. So, you know, it's
something that's very, very tiny, but still it's, I mean,
you can see a strand of spider silk with your naked eye, and
these are fairly close to that, maybe half or a third of that.
So far, what I've shown you are simple sine waves that have
single unique wavelength. And this the simplest possible type
of light wave, but it isn't at all a common type of light wave.
Most light waves contain many different wavelengths with a
different amount of energy in each this is typically
visualized as a spectral power distribution, or SPD, for short.
As you can see in the upper left, the SPD for this
particular wave shows that this wave's energy is all in a single
wavelength. It's all in the single wavelength in the green
part of the spectrum. And this is typically what you will see
in light emitted by laser. So it's sort of a Dirac delta
function in the SPD. In actuality, lasers actually have
a little bit of bandwidth, but they are extremely narrow. Now
here we see the SPD is for red, green and blue laser that h
multiplied by factor and added together to produce the SPD on
the right. Now this kind of spectral power distribution is
similar to what you would see in life a laser projector. And
laser projectors are starting to show up in higher end theaters,
newer theaters. They offer wide contrast, wide gamut. They have
some advantages. So this is an extremely spiky spectrum, and
it's still very simple, and it's not one sine wave, it's three
sine waves. And if we look at the actual waveform, we can see
that after adding up these three simple sine waves, we end up
with something that maybe looks a little more complicated than a
single sine wave, but not that much more so. I mean, you can
see some underlying frequency, and there's some larger reads
there. However, most light that you'll see in nature doesn't
look like that. SPD looks more like this. This is the SPD for D
65 which is a standard spectrum for white light, outdoors light,
and you can see also the waveform that it will create,
which is, of course, very complex. Basically, the broader,
the more detailed SPD, the more chaotic looking the way from a
form will be, and the less a simple sine wave. Now an
interesting thing is that although these two SPDs could
not be more different, one is extremely smooth and broad, the
other one is three delta functions, but they have the
exact same color appearance to humans. Now, the y axis isn't at
the same scale, so obviously spikes are higher to compensate
for the lack of width, but the fact that human color vision
cannot distinguish between these two signals tells us that human
color vision is incredibly lossy. It maps the infinite
dimensional SPD down to a three dimensional perceptual space.
Now if we look at this wave form in vacuum, it will propagate
forever. The electric and magnetic wave will sort of
enforce each other, and they'll just keep on going and going but
for rendering what we care about is what happens when this light
wave interacts with matter. Now what happens is, when an
electromagnetic wave hits a bunch of atoms or molecules, it
polarizes them. That means that it stretches and separates the
positive and negative charges and forms dipoles. This absorbs
energy can then come away, and this energy is radiated back
out. You can imagine, like a spring, the dipoles and this
energy is irradiated outwards. And sometimes some of it is lost
heat. Other times, all of it is preserved and radiated outwards
in new waves going in all kinds of directions. In a thin gas,
molecules are far enough apart that you can treat them
individually. And then there are fairly simple physical and
mathematical formulations that understand what's happening. But
in other cases, in dense gasses, liquid solids, the combinations
of the deckles interact with each other, and the waves
interfere with each other. And the whole thing is, in the
general case, much too complex to accurately simulate. So the
science of optics, in this case, physical wave optics, in order
to tame this sort of chaotic situation, they adopt certain
abstractions, simplifications and approximations. For example,
they have the concept of a homogeneous medium through which
light travels in a straight line. Now, homogeneous medium is
an abstraction, obviously, because matter composed of atoms
can never be truly homogeneous for all scales. But in practice,
this abstraction works quite well for materials that have
uniform density and composition. The optical properties of this
homogeneous medium is described by its index of refraction, or
IR, for short. This is a complex or, in other words, a two part
number. One part of the IR describes the speed of light
through the medium, and the other one describes how much
light is absorbed by the medium. And there are many media that
are completely non absorbent, and for them, that number will
be zero, localized in homogeneities in the medium is
you have to model things of a completely homogeneous medium.
So the way that optics models these localized and
homogeneities is as particles. So the assumption is that we
have these abrupt IO discontinuities, and they
scatter the incoming light over various directions. This is
similar to individual molecule polarization that we discussed
earlier, but these particles can be composed of many molecules,
and there are some formalisms in order to handle all this
situation. Again, it's a bit of an abstraction over what's
actually happening. Now, the overall appearance of a medium
is determined by the combination of its absorption and scattering
properties. For example, a wide appearance, like the whole milk
in the lower right corner, is caused by high scattering and
low absorption. You sort of can sort of see absorption and
scattering as to add independent axes here. And if a liquid is
colored, that means it absorbs light more readily in some
wavelength than others, so it's sort of spectrally selective.
Now, we've briefly touched on participating media here, but
actually the rest of my talk will be focused on object
surfaces, which is a more common and basic case in memory. Now,
from an optical perspective, most important thing about a
surface is its roughness. No surface can be perfectly flat.
At the very least, we have irregularities at the atomic
level, irregularities that are of similar size or smaller than
light wavelength. We will. I will call this nano geometry,
and these cause a phenomenon called diffraction.
There is something called the Huygens Fresnel principle that
can help understand the diffraction on the intuitive
way, it states that each point on a planar wave, you can
imagine, each point on a planar like wave is the center of a new
spherical wave that's being emitted, and then these
spherical waves will interfere with each other in order to
create a new plane wave. Now so far, this hasn't gave us
anything in terms of intuition. We went through a plane wave,
through a bunch of sea waves, back to the plane wave. But
where this, where this sort of mental picture helps is when the
wave hits an obstacle, and that's when you get diffraction.
So when the wave hits the obstacle, then you imagine these
spherical waves, and then one side of it, the spherical wave
that's on the very corner of this obstacle, it doesn't get
canceled obvious. There's no other waves next to it, and you
see the light is kind of bending around the corner. It's actually
not traveling a straight line. And that's an example of
something you don't get with the standard geometric optics. And
the effect of this will be to slightly soften shadows. Even if
you have a point light, your shadows will be very slightly
soft into this effect. Now what's more interesting for
reflectance, which is what this course, is about, is diffraction
on the surface, the irregularities of snail geometry
that's on a surface. And for this case, I'm going to look at
an optically smooth surface. An optically smooth surface is
defined as a surface where all the irregularities are in the
Nano geometry category. So all the irregularities are smaller
than the light wavelength. It's actually not hard to polish a
surface to that degree. Commercial grass is commonly
polished far smaller than a visible light wavelength. And if
we look at this plane wave hitting this surface that's
irregular on a scale of 10s or hundreds of nanometers, then we
can apply the same Huygens principle. And so we see that
every point in the surface is emitting its own spherical wave.
And this looks a bit chaotic, because it is. Some of these
surface points are higher, some of them are lower. That's due to
the Nano geometry, and then all these screw waves will sort of
interfere and reinforce each other, interference. And you'll
get this kind of complexity, structured wave front. This
little drawing actually doesn't do justice, and you'll end up
with some amount of the light scattered in all kinds of
directions. Now, the smaller the Nano geometry, the less likely
fraction, the more of it will be reflected, sort of in the
regular specular way that I'll talk about soon. So it's really
a function of the height of the bumps. And if you have a
surface, that's, I think the term is super polished. I don't
know if that's a technical term, but I've seen it used on several
websites. It is possible, with some effort and expense, to
polish a surface to the level of individual atoms, then the
scattering that happens on a surface like that will be small.
It'll be around 1% or half a percent of incident light, but
it's definitely still measurable. So there's no such
thing as a perfect surface. Now we're going to take a break from
wave optics and move into the more familiar, geometric or gray
optics, which is a more simplified model, and it's
really the model that all of the geographics, with a handful of
exceptions, has been using since forever. One simplification we
make is to ignore nano geometry. Basically. As far as geometric
optics is concerned, if it's smaller than a light wavelength,
it doesn't exist. Any optically smooth surface will treat us
this mathematically perfect, abstract, flat surface. Now, it
can be shown in the equations governing electromagnetic waves
that such a perfectly flat surface, ideal surface, will
split light into exactly two directions, reflection and
refraction. Now, most real world surfaces aren't optically
smooth, but they have irregularities of the scale
that's much larger than the light wavelength, but still
smaller than pixels. So we'll call this micro geometry to
differentiate from nano geometry that was smaller than light
wavelength. And this micro geometry variation, it doesn't
cause diffraction. What it does, it simply is tilting the surface
in various directions. And since, as we saw here, both
reflection and refraction direction depend on the surface
normal, on the surface orientation, then the micro
geometry is simply changing the local normal at a very small
scale, and you end up with reflective rays, even though
each specific point on the surface is only reflecting the
incoming light of a single direction, because a pixel
covers a lot of bits of surface angle in different directions,
you end up with a sort of statistic aggregate. Now this is
roughness on the microscopic scale. If I look at these two
surfaces, then to our eye, they seem equally smooth. They seem
like these nice, you know, smooth hemispheres. One has a
hole in the middle of the map. They're very similar shapes. But
in on the microscopic scale, they're different. This top
surface is slightly rough. If you took a micro micrograph of
it or micro photograph of it, you'd see these sort of gently
undulating hills, as it were, and that means that incoming
light rays will hit surface points that angle slightly
differently and will bounce out in slightly different directions
and end up with this sort of narrow ish cone. And that's why
the reflections are only slightly blurred the surface on
the bottom, however, it is on the micro scale very rough. If
you looked at the microscope, would look like valves or
something. And so every bit of surface by the light is angled
in a very different direction, and the light spreads out in
very white color. Now, in the macroscopic view, we don't model
the micro the micro geometry explicitly between it
statistically and view the surface as reflecting and
refracting light in multiple directions in a cone. And the
rougher the surface, the wider this cone will be. Now the
questions we've talked about reflective light, what happens
to refractive light? And this depends on what kind of material
the object is made of. Light is, since light is composed of like
magnetic waves, the optical properties of the substance are
closely linked to its electric properties. And we can group
materials with the three main optical categories, metals or
conductors, dielectrics or insulators and semiconductors.
And really, in games and movies, you don't see a lot of exposed
semiconductors lying around. So we can, in most cases, ignore
that situation and just divide it into metals, non metals, that
has advantage of being way more intuitive to an artist and
talking about dielectrics and the like. Now, metals
immediately absorb all refractive light. Basically,
there's a CS, the electron that sucks up all the electromagnetic
energy, and it's gone never to return. Non metals, however,
behave like those cups of liquid we saw earlier. Effectively, you
have this participating medium underneath the surface that the
refracted light is participating, and the refracted
light is scattered or absorbed, or scattered and absorbed, and
you have all the same variations we saw in those cups of liquid.
If the object is making a completely clear substance, like
glass or liquid, the light will just keep on going. But if
there's enough scattering, which most objects will have, some of
this refracted light will be scattered back out of the
surface. And those are the little blue arrows that you see
coming out of the surface in various directions. And I've
kind of tried to visualize the fact that the light internally
is getting selectively absorbed, so it's getting tinted blue. So
the arrows are sort of the yellow arrows turning blue and
blue and bluer until they get back out on the surface. Now
this re emitted light comes out at varying distances from entry
point. And you can see the L bars show one way. One Ray is
coming up really close to entry point, one ray coming up a bit
farther. And this distribution of distances depends on the
density and other properties of the scattering particles. Now if
the pixel size or shading sample area or distance between shading
points the shading rate, or however you conceptualize that
that's sort of the area of interest for shading. If that
pixel size is large, like the red border, green circle and
image compared to the entry exit distances, then we consume
distances are effectively zero for shading purposes, we can't
resolve the fact that the light is coming out in a different
point that it's entering. So in that case, by knowing the entry
takes a distance, we can compute all shading locally at a single
point, and the shading color is only affected by light that's
hitting at one point. It's convenient to split these two
very different light material interactions and different
shading terms. So we tend to call the surface reflection,
term specular, and the term resulting from refraction,
absorption, scattering and re refraction, we call diffuse.
Now, in the other case where the pixel is very small, or small
compared to the end to the exit distances, so we have the red
border green circle again, but it's much smaller in this
picture compared to scattering distances, then we can't tweak
the shading as all happening the single point. We need some
special subsurface scattering rendering techniques and even
regular diffuse shading, the physical phenomenon is the same.
It's still subsurface scattering. The only difference
between something where you're running a subsurface scattering
shader at one point where you're running a regular diffuse
shader, is the difference between the shading resolution
and the scattering distance. So it's not true to say that this
material is a subsurface scattering material. This all
depends on the distance to the camera. Right? If you have
plastic far from far away or from arm's length, then it acts
like diffuse. But if you're looking at Super up close, like
in The Lego Movie, then you can see visible diffusion happening.
And the same thing happens in first human skin has physical
scaling behavior. But if you're looking at human from far away,
you can just shape them as a purity gift. Now so far, we've
discussed the physics of like pattern interactions. Of course,
to implement them in a game or film render, you have to
you with a vendor, yeah, is he making some useful points to
help the understanding of what we've been talking about.
Anyway, we're out of time today, so thanks for today. Have a good
weekend. Conclude our material with a look at the the area
lights, chapter 12.
So does that include dome area lights? Just area
so we'll deal with area lights.
Okay, yep,
thanks again for today. Take care, everyone.

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