Blender 2.7 Tutorial #46 : Eliminating Fireflies (Render Noise) #b3d Video Lecture | Learn and Master: Blender (English) - Professional Skills

hello and welcome about 46 my BtoB is
blender 2.7 in this video I'll be
talking about fireflies and how to
eliminate them now what does that be are
fireflies well they're an artifact that
shows up when you render a scene using
these cycles render engine some of the
time to show you what these look like
I've got a really simple scene here I've
got basically an enlarged stretched
default cube with one of the faces at
one and cut off and inside this cube
which will be acting as our room I have
a simple small flat square plane that's
one tenth of one button unit on each
side so it's very very small and on that
plane we have in Mission material so
it's at a hundred strength which means
it'll be quite bright or sufficiently
bright to light most this room I've got
a camera set up at the end of the room
to point into the room let's go ahead
and render so go to the camera tab and
the render section and press render
so go ahead and render it out the scene
at the default settings for blender in
other words we have ten samples and what
you can see is that we have all these
white specs all over our image and these
are fireflies these are artifacts that
we obviously don't want in our scene so
how do we fix this problem how do we
have the same looking the way we wanted
without all these specs all over our
scene well your first inclination would
be partly right if you thought right off
the bat that hey just increase your
samples that might fix it let's go and
see if that works now what does that
mean well under the camera tab under the
sampling area basically what this does
is this render setting here is set by
default at 10:00 it's the amount of
times this tent number is the amount of
times that the light is calculated per
area on your screen to make the image
less grainy and more accurate and more
clear the higher this number is the
nicer looking you're under will be but
of course it'll make your render take a
lot lot longer by default it's 10:00 I'm
go ahead and type in 200 and I'll press
render again
all right so we've got a hit and figure
out the exact same scene but this time
instead of using ten samples we set the
scene to 200 samples and we still have
that grain if you think back to when we
use ten samples this is what we have we
had an image with lots of these white
dots or fireflies on it and at 200
samples it gets better but it's still
very very grainy so why is this
happening well for one we're using an
object in other words a mesh object that
has a mission shader on it and that
object is very small and it's very close
to the ceiling in my room so though
several things going on there we're
using a mesh with an emission shader on
it the lamp is very small and it's very
close to one of the other main objects
in the scene
in this case the ceiling what would
happen if we were to move that lamp
object or the mesh with the ignition
shader on it away from the ceiling well
let's go ahead and take a look I've got
a head of Ritter that exact scene out
and as you can see the fireflies pretty
much disappear crap there are none in
this example at all this is great but as
you can see it's casting sort of a
shadow where the objects edge is not
really casting as much light as opposed
to its up-and-down surfaces so I mean
that's a good thing we know that we can
get rid of these fireflies by moving
away and you lamp from any object great
but what if you want the lamp object to
still be up near another object like a
ceiling
well another solution is to make that
object larger so what I did is i scale
this object out by I think about 10
times now put it back up to the ceiling
so our light is now back at the ceiling
it's just lot larger and this is what we
get same number of samples again right
up to the ceiling but we get no
fireflies there is a little bit of noise
here though as you can see up near the
corners it's a little bit grainy
although still very good and I think
that Karina's would go away if we turn
our samples up to let's say 500 or a
thousand or even 2,000 it would improve
so that's one solution you can make the
object larger or you can move it away
from the object so it's not casting that
a hotspot it's not really brightening up
an object making that object be
bounce light essentially but a very
overexposed balanced light okay so
what's another solution if none of these
work for you or if you'd rather use a
proper lamp object you'll also get
better results what does that mean well
our light source right now is a mesh
it's just a flat plane with one polygon
four edges and four vertices there are
lamp objects though as you should know
if you haven't got ahead and watched my
video on lighting and rendering in
cycles I'll put a link to that on the
screen right now lab objects are even
better to use and they don't show up in
your scene as a large white object so if
we go to the add menu and you say add
lamp and then an area lamp you can unset
the area of the lamp in other words the
surface size to the same I believe this
is two by two and with that we get this
result it's even better that's even less
noise there are no fireflies the lamp
object is in the exact same spot and I
think a fable about the exact same size
and the scene looks even better so what
you could do here is you could probably
composite in another light object up
here if you try to put a light object in
other words like an orb with a white
material on it it might actually cast
its own shadow and we're not going to
deal with that in this video but as you
can see we're getting a good result here
it just works what happens if we scale
that light down back to the original
size and the words back up to that small
size of the original light well that's
what you get it's just a very slight
difference from that one which is the
large light to this one with the small
light you can see as I toggle back and
forth that the like it's a little bit
dimmer and fades off more at the side so
that's my room example switching themes
now I want to show you a few other
reasons why you might get fireflies or
noise in your renders I put a simple
scene set up here it's got a few objects
it's got a ground plane a couple of area
lights and a lamp if you were to go
ahead and download the saqqaq file if I
link that in the description area below
this video let's go and take a look at
it scene I have of course a few area
lamps and I believe they are of size 1.0
they're Square area lips I've got a few
objects a monkey head a cylinder and a
comb all three of them have different
colored just very very simple diffuse
VSD
materials and the ground plane is going
to be causing a lot of our issues our
ground plane has a glossy a shader on it
you can add it of course under the
materials tab instead of a diffuse
material or shader we have a glossy one
here so what happens when we try to
render well I'm going to go to my camera
tab and just make sure my render
settings are at ten which they would be
by default and if I press f12 or go and
press render here you'll see what the
scene looks like I have a lot of
fireflies or a lot of noise or speckles
on it and I don't want that let's go
ahead and try turning up the number of
samples to again 200 so under the
sampling tab under the camera tab render
samples we'll set that to hundred and
I'll go ahead and press render so it's
finished rendering out and as you can
see our situation didn't improve very
much we have a lot of speckling going on
here we've got some noise or fireflies
at the base of these objects all around
the cylinder and especially on the
underside or the cheek of the monkey
head what's going on here well the kind
of noise that we have now is called
caustic noise what is that well if you
think of what caustic light is you might
think of kind of the Marbley reflections
that you get if you were to look under a
pool or just basically in any kind of a
pool deck where you have light passing
through or being reflected by a glossy
material or traveling through a
transparent object with a different
amount of density in it that causes that
kind of marbling sort of a light blunder
doesn't really handle those very well so
let's go ahead and try turning off
caustics or caustic lights to do that
I'll go to my render tab and under the
light paths area we can see that we have
reflective caustics and refractive
caustics now what these mean are if you
have a scene with a transparent object
like glass object you might get
refractive caustics which means the
light actually bends as it's going
through that material and so if you want
to make sure that that's not a cop out
you would uncheck that if you have
anything that's glossy or reflective you
might get reflective caustic closer to
what we're seeing here right now with
all of this
so I'm going to uncheck reflective
caustics and we'll go ahead and press
f12 or the render button again and see
if we get a better result so as you can
see our noise is gone and our problem is
solved but wait our scene doesn't look
as good anymore if you notice underneath
the monkey head we aren't getting that
nice bounce light that we had before
although it was all especailly it's what
we would probably want to make to seem
more realistic in other words we would
have bouncing light coming off of a
reflective ground up onto the monkeys
underside of his cheek and that's a good
thing so how do we get that back we're
not getting the noise if I recheck
reflective caustics and press f12 or
click render we get that nice bounce
light back under the monkeys cheek add
some of the reflections back on the
floor underneath the monkeys head so how
do we solve this well there are many
ways I wanna show you the most easy one
first and we'll go into something a
little more complicated to fix this
problem all we have to do is under this
light path section under the camera tab
we can turn up filter glossy now what
this does is it basically takes the
light as far as I can understand it
takes the light after it bounces once
and it sort of blurs the light now
unfortunately the more you blur that
light
in other words light that's after one
bounce the less accurate it becomes but
the more you won't see these speckles so
I'll go ahead and try out this filter
glossy 20.5 the default is zero and if I
press f12 or click render again as you
can see now we have very few speckles we
could turn the filter glossy setting up
to one or maybe even a little bit higher
but you would start to notice that the
light being left look a little bit more
muddy you wouldn't get quite the nice
definition of the brightness under that
edge right there it would start to look
much more even which is what you might
actually want let's go ahead and try
that up I'll turn the floor Gossie up to
one and I'll go ahead and press render
again
as you can see now we have another good
result here if you really compare the
last two renders of this render versus
this one you'll see again that we don't
have quite the same definition under the
monkey's cheek but again we have a
little bit less noise too so it's up to
you what result that you want there is
another way though of course to fix this
problem in fact there's many ways I'll
show you one more I'll go ahead and turn
filter glossy back down to zero which of
course will give us that noise back but
what I'll do this time is I'm going to
make it so that the floor does not act
as a glossy material for the other
objects in the scene but we will still
get to see that glossiness if you think
back the video we'll talk about sky
color versus skylight I showed you how
to use the light paths node in order to
stop reflective light from one object
from bouncing onto another object well
we can use that light pass node in
exactly the same way here so I'll press
escape on my keyboard to see my scene
again and I'm actually to change my view
from just material down here to rendered
so we can actually see what it looks
like and I'll press 0 to look to my
camera with the floor selected and it
will be easier to do that if I actually
have two windows here with the floor
selected I'm going to go ahead and take
a look at these nodes we have a glossy
shader here and of course a material
output but what I'm going to do is I'm
going to make another shader a diffuse
white shader and have that color be the
one that's reflected up under the monkey
cheek and on the rest of the scene so
let's go ahead and press shift 8 and I'm
going to add another shader I'm going to
add a diffuse material here and I'm
going to add another so shift a and add
another mix shader'
now what this will do is it will blend
these two together and then we'll use a
light paths node to make it so we can
only see this one but the other objects
in the scene only see this one so I'm
going to drag the mix shader' into that
noodle there and then connect these two
and I'll press shift ain't know what you
can actually see here is now we are
seeing kind of a mix between this white
or almost white alternate all the way up
actually like that what I need to do now
is add a light paths node so I'll press
shift a
and I believe it is under input there it
is light paths note so I'll add that
click to put it right there now we're
going to do here is we're going to make
it appear as a diffuse material to other
objects in the scene so I'm going to use
this little note here and drag it right
here and as you can see now we're
getting a really good result we have our
glossy material on top we have our
diffuse white material on the bottom
we've got our plugged in light paths is
the view stray into the mix shader'
and if I go ahead and press f12 so as
you can see we've got a good-looking
scene we haven't filtered any glossy we
haven't turned off any caustics and
that's because the ground is now just
acting like a white floor bouncing up
that light like I normally would on the
under face of the monkey I think we have
an a little bit too much light here so
what I would probably do is press escape
and turn this diffuse color down to a
lighter shade if I make it much darker
or lighter shade of grey and then I
render again you can see now that we
have a little bit less light under this
cheek which means that we have a lot of
control over the amount of bounce light
in our scene
anyways that'll be to this video thanks
for watching and I'll see you next time
you