Merge & Apply in Resolve & Fusion: In-Depth Look at Alpha Manipulation, Screen, Overlay and more

Merge & Apply in Resolve & Fusion: In-Depth Look at Alpha Manipulation, Screen, Overlay and more


I don’t want to endorse graffiti nevertheless
let me paint a smaller one next to me. Welcome to a short tutorial about the merge and apply
modes in Fusion. So here it is, the most basic compositing tool in Fusion – the merge node
and of course you all are familiar with the standard I suppose. If I have a foreground
A and merge over the background B, then the result is, I see the foreground and where
it is transparent I still see the background, or the background shines through. So far probably
not surprising but they’re actually quite a lot of settings for such a simple operation.
Now in this tutorial I want to do 2 things: I want to discuss about the apply mode. These
different ways how the merge happens and different computations. You know these maybe from Photoshop, there they’re called I think blend modes or blend operations and they’re different modes which
are quite useful I will show you a few examples how you can use them for different compositing
tasks. The second part which I will actually start with, so I should say the first part of
this tutorial, I go through these settings and these are there to decide how the alpha channels
operate and how you can manipulate the alpha channels in the normal compositing operation.
On top you have just for completeness you have a transform. This is transforming the
foreground on top of the background. You can do this with the separate transform node as
well and on the bottom you have which algorithm is used in this transform, so how to interpolate the resizing and so on so this is not the topic here. The topic is purely
the middle. So let me start with the operator and different alpha manipulation settings. Now
operator over is the standard if I change the operator to In that means my foreground
gets put into an area defined by foreground and background so it gets just thrown inside
and actually let me make the foreground a bit transparent to illustrate a bit more, so
you see the alpha channel is now only a determined by the foreground and the background is only
used to determine this area where the foreground goes in. So that is what In means. Another
usefull thing is Atop so this means I keep the alpha channel completely from the background
and I throw the foreground only into the area defined by the background. So these I think
are Over, IN, Atop are the most common ones Held out and this Exclusive Or these are a bit exotic, maybe I would say this is more like for logical operations or maybe every now
and then you can use it. So show the foreground where there is no background or show foreground
and background everywhere where there is is not foreground and background. Well, okay doesn’t
sound very natural but sometimes you have some logical scenarios where you might use this in channel logic or
similar. Now let’s have a look at these settings here and these settings are mostly
applicable only in the Norman mode and to illustrate this we now need a bit of transparency to
see what’s happening, so that me again make the foreground transparent. These settings sound
a bit like color settings right? Gain and burn and that’s actually what is happening. You’re doing kind of a color correction off the alpha channel inside the merge in
different ways. First of all Subtractive, additive, this is the distinction between multiplied alpha, premultiplied and unpremultiplied alpha. If you have never heard
the terms this might warrant a separate tutoraila but just to give you an idea. This picture
here has a alpha value and now you should look into this area at the bottom where the
values of being displayed this has now an alpha value of around 50 percent of 0.433. However the red value is the 1.0 and this is a bit unnatural because typically
if a picture becomes transparent than the picture also becomes darker or the colors become
less intense, so when I merge an image with transparency over another image I would expect
that the color is no longer like 1.0 but that the color also dims and what is typically
happening when I make a picture transparent I multiply the color values with the
alpha values. However, this is a compositing right, so when you get pictures from
a 3D application or from Photoshop or when you get an image and an alpha channel separate, maybe from a keying process this may or may not have happened. So if you have an image
which does not have the alpha values multiplied onto the color values then you can do it
actually inside the merge. If I look at this picture I still have my foreground with the
red color value 1, but if I go to the subtractive completely. I see it gets darker and I see
in the values red is now point 0.433 which exactly my alpha value so it got multiplied
with the alpha. So if you have images which were not multiplied before you can do it this
way. Another thing is if you have for example a Keying example. It’s not multiplied and
you see you can use this to tune the edges sometimes. So between the multiplied and the
unmultiplied – Premultiplied and unpremultiplied These words are really terrible, but that’s how it’s actually called, anyhow so on the scale from subtractive to additive
you go from darker to normal or to not multiplied and since the transparent areas
are typically the edges, if you have any effects of green screen a similar, this often means
that you often have control over how the alpha how the transparent edges are being
handled. Second part here, alpha gain, this is indeed just a scaling off the alpha value
of the foreground. So here I go if I put it all the way to 0 my alpha everywhere where it’s
transparent goes all the way down to 0 so again if I have semi transparent areas and so on, I can can scale them and thereby control the merge. Burn In is kind of
the opposite. Alpha gain relates to the alpha of the foreground burn in relates
to how the background color is mixed together based on the foreground of the alpha. And if that
sounds theoretical let me just show you. So if I put the burn in, you see that the color
gets stronger and more intense and if you look at the values you see that the values
were now added. My background had read 1 blue 1 and in the combined area I have
read 1 and blue 1 and alpha 1.433 so the alpha is now even about 1, so in the complete burn in
1.0 version, what I’m doing is actually adding it’s a add or plus operation. it’s not on a typical
compositing operation but again you can use use this merge for this kind of mathematical, logical
operations to add channels together on some things together, the option is there and
sometimes you might use it just to strengthen or to change the way the colors are being
applied. Okay so this is the alpha manipulation Blend is of course the usual blend you have
it in practically all tools it just says to what percentage should this toool actually work. Blend 0 means I have completely my background this tool does nothing blend 1 means this
tool does everything on top and in between you have the scale and of course this is also
the tyipcal blend between foreground and background that you can animate etc.
Okay this was the theoretical part about the alpha channel. Now. I want to go
over to the more practical part and discuss a few of these apply modes and that I think
is best instead of telling it in theory showing you examples and the first example I see
here is called screen and there is areason for it I believe and to make it super obvious
I have – a screen. Okay so and if I have the screen in the background and screen my foreground
image using the screen operation than this is what is happening. And the reason why this
is really looking like a cinema projector now is that the screen works really well
with adding light effects. So if I add white it becomes white if I add black, nothing happens and so on, so I add to the highlights at to light colors and this works pretty well
with light effects of all kinds projector is an obvious example another example could
be lens flares for example, here I have some crazy lance flares and an equally crazy
scene and if I screen those two together. And maybe change the gain or blend, doesn’t
matter dial it down a bit I get my light effects on top. Okay, the result looks
ugly but I think that’s not related to the screen but to the used images, never mind,
so the screen for any form of light effects highlights, adding on top of the highlights,
making things only brighter, that is when you want to use the screen. The complete opposite
of the screen is the multiply. And here’s an example for that, I have a wall and on
top of that wall I want to paint my logo and this should only get darker and if that’s what I want, then I can multiply. Now the colors get multiplied. Multiplying by white will do
nothing, multiplying by black is black and in between it just gets darker, right. So
this is the multiply, any form of painting on backgrounds etc. like with a blocking paint that kind of thing looks like you multiply. If you want to combine screen
and multiply that’s also possible that is where we have the overlay now this is actually
the example you saw in the introduction. So I have my graffiti and if I merge it over
the wall, then this is how it looks like, let me zoom in a bit. So overlay does a mixture
of screen and multiply. It preserves the highlights and it preserves the shadows. So in this case from the wall you still see the dark areas here shining through, you also see the
light areas being preserved. So with multiply for example I get this, I get all
the dark areas getting even darker I don’t see the the shadows properly any
more and the highlights, same for screen so it gets super bright but here, I
keep the the dark areas but the brightness may go too high. So overlay is really the
combination of the two, it keeps the highlights and the shadows from the background and merges
the foreground into it. And of course you might still want to manipulate the blend or gain and do some color correction and so on. Now, in my list I skipped one mode and
that was the dissolve and just for the pure fun of it I show you what it does it has
a gain value, if it’s 1 it’s like a merge, if it’s 0 it does nothing and in between
I can animate it and this is what I’m getting and I have really no idea why I would ever
use this, but just to have the feature, now you know it’s there. Okay let’s continue with
something more useful there are – if I jump a little bit there are these two darken and lighten and these two blend modes or apply modes they can sometimes save you time in compositing and the example I’m choosing here is a sky replacement, I have this very simple image with the uniform sky and I have a cloud image and now I want to add a bit of
texture into the sky and want to see more from the clouds. So the first thing I can
do here is just use lighten. And what you see here is it takes, it compares the foreground
with the background and it takes the minimum values, so whatever value is lighter gets chosen. That’s it. So in this case the clouds here are lighter than the clouds we
had in in the background in this area and that’s why they’re being replaced here. The
good thing about this kind of operation is it gives you often very clear boundaries so
you don’t get get some form of merge, you get really a replacement and
the replacement includes the edges. Right. So in this case it works quite well
in this area doesn’t work so well over here. So let’s see what the darken does instead. If I go for darken, I replaced the darker areas it’s the exact opposite, so I’m taking the
minimum values, I take the values from this if it’s darker than the original otherwise I
take the original value and I see here at the horizon that my rectangle mask is not
really working, so I just put down a bit and I see another great thing. The horizon is
typically darker than the sky. So I don’t have any problem at all at the horizon I don’t
get any any bad effects, I don’t need to rotoscope or anything because the horizan is darker, so it doesn’t get replaced, it remains intact and only the sky gets replaced and for most of the picture it works and in this area I’m running into some trouble
here because here the the separation between light and dark areas is not not good enough.
So whether lighten or darken really works it is very sensitive to the color of both
pictures but if you do have this light / dark separation and horizons I think are typical
examples where you often have it, objects in the sky like single clouds or airplanes or something in the sky often in these cases you might have the separation between light and dark
and then this can actually be a useful. Now there are a few more tools here and I think they are mostly here because you know Photoshop has them and people say the more the better right. Well, Soft Light and Hard Light this is suppose like for diffuse light sources or very
harsh light sources which you can add like a spotlight effect or something like this
maybe you can use it every now and then. Color dodge and burn, yes I mean dodge and burn comes from photography but I rarley see that in a compositing context, I’m not sure I’ve
ever used it, of course you can always try if you want to achieve some some funny effect. If you have a really realistic example, please tell me in the comments below, I’d love to
hear it. If I come up with an example in the future I might have to do part 2 for this
tutorial but for now even this tools here, Hue, Saturation, Color, Luminosity… so basically instead of the alpha channel you’re using Hue, Saturation to decide how to combine
foreground and background and almost always this gives stupid results I mean. Saturation,
Color, again if you have some clever a real life example where you use this please let everyone
know and if not enjoy that there is the extra functionality. Okay, let me stop right here,
so much for a foundational discussion of the merge tool. So this time I really started
from the simplest example to discuss effects on the alpha channel and then going into the different apply mode settings, I hope you enjoyed this style of tutorial, next time I will again
take a single effect and walk you through step by step from scratch. I hope you enjoyed it, if you have any questions let me know. I hope you enjoyed this tutorial if you’re
looking for a more systematic training check out the video over here and see you around
next week.

9 thoughts on “Merge & Apply in Resolve & Fusion: In-Depth Look at Alpha Manipulation, Screen, Overlay and more

  1. Hello, not sure if you are gonna see this but.
    Im used with Nuke and just started with Resolve.
    Is there a Node kinda like Shuffle from Nuke?
    Thanks

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