Green Screen Composite
One of the things everybody always wants to do in Fusion is a green screen effect. Now, a little disclaimer. A green screen effect is very complicated most of the time. It's not quite as easy as just clicking on green, and everything looks great. There's usually quite a bit of work that it takes to get your transparency just right. That said, this is a pretty easy example, and you can at least kind of get an idea of the workflow of kind of how things work inside a Fusion when it comes to green screen. So, I have my green screen clip here of our businessman, and I'll switch over to the Fusion page, and he is very excited. He's very excited to be here wearing a suit. Good, good for him. So, the first thing that we're gonna do is kind of put this on the upper layer, because really, what we want to do is put a background behind this guy. So, I'm gonna start out with a background. So, I'll take my background node like this, and I'll disconnect my media in. And I can take my media in and mer...
ge it over our background, and take the merge in put that into media out. Now, nothing's really changed except for, we have a little bit of space between our background and our merge, to be able to add whatever we wanna put behind him. And before we can see any of that though, we need to get rid of this green screen. So, I'm gonna select media in, and hit SHIFT space bar. Remember, that brings up our select tool menu, and I'll type in key, K-E-Y. A key is just the term for selecting a certain color. Okay? So, I'm gonna use an effect called delta keyer. Delta keyer is pretty much what you use to get rid of green screen here in the Fusion page. And we'll run our media in through that effect. Now, nothing's happening because we haven't set any of our controls here in the inspector. I'll click and drag this eyedropper, and as I sample the green screen, we can see that it kind of gets rid of it. Now, what I'm gonna generally wanna do is get pretty close to our talent here. Just because that's where we are really gonna want a good edge. Now, if we were to select our background and change the color here to, I don't know, like orange-ish. Then, we can see that, yes, it's cut him out of the background. But we also have a little bit of noise and kind of weird stuff happening here. And it just doesn't quite look great. And we can get a little bit better view here if we look at the transparency channel of this effect. We can do that by hitting 1 on the keyboard, and bringing it up over here. And then, clicking on this viewer and hitting A. And that will bring up our black and white image. Now, if you do some compositing, you'll start to see these kind of black and white images. These are called mattes. And basically, what that works is it's a channel in an image that controls the transparency. So, the white in a matte is completely opaque, and the black is transparent. So, you can kind of think of it as white is on, and black is off. So, we want this image to be on anytime that there isn't a green screen, and off for everything that was green. Now, ideally, you want this to be perfectly black and perfectly white. And we have all this gray around here. That means that we're going to have a key that just does not look good. So, we have to refine our matte. So, I'm gonna take this delta keyer, and there are a few different things that I can do here. I'm gonna switch over to this third icon here, where it says matte. And one thing that I can do is adjust this threshold. If I take this low threshold up, that's going to make more things black, and that's going to fix a lot of the problems for this shot. This is, for the record, a pretty nice, pretty easy shot to key. It will usually take a little bit more work than this, but for now, we'll just use our low threshold and our high threshold to make sure that this is a nice black and white kind of matte. And now, we're gonna have a nice transparency here that we don't see a lot of green fringe around him. Even his hair and everything looks pretty good. This is a pretty easy matte to adjust. So again, it won't always be this way, but if you shoot it right, sometimes, it can be about this easy. So, now we have this guy isolated. Now, we can put something in the background that looks a little bit more realistic, maybe than this kind of orange-ish background. So, to add something new into the Fusion flow here, we go over to the media pool, and grab whatever we wanna put in there. I'll just grab this still. I can grab it from the media pool and just drag it down into the nodes. And that will make a new media in node. Remember, a media in just takes an image usually from the timeline, if you're just opening it from the timeline, but you can also take an image directly from the media pool. I'm gonna close the media pool. And let's go ahead and rename this. I'm gonna hit F2 on the keyboard, and call this Background Image. Just so things don't get too confusing. And I'll rename this one, Guy. So now, we need to put our background image behind our Guy. We wanna be really careful inside a Fusion when you bring in a still, especially a high resolution still. Because, oh, it looks like this is white here instead. I don't wanna look at the alpha, I'll click on this and hit A to switch that back over to the color preview. If you bring up a still, especially a high resolution still, it will bring it in at its native resolution, which is fine except for, Fusion is a little bit picky with how things are sized. And so, you really wanna make sure that everything is kind of using the same dimensions. And if you have something that's bigger, you sorta want to crop it. One way to do that is just to merge this over a background. So, right here in the upper right hand corner of our screen here, we can see this is 5900 by a 3900 ish (chuckles) huge image, right? If we take a background, and we merge this over a background, and we open our merge here in the left viewer, we can see up here, it's 1920x1080, which is the resolution of our timeline. So, that's the same resolution as everything else, which means that it's going to play nicely. Now, we don't need to make another background 'cause we already have a background here. So, I'll just merge this over our background like this. And okay, maybe we like that. Or, maybe we want to change that around. Again, I can grab the merge and adjust the sizing here and the merge, but it's a good idea again to make a transform node, so I'll hit SHIFT space bar, and type X F. Just so we always know what's going on here in the flow, and I'll take the size down. And now, we have this nice kind of little background here. So now, we have our background, and we have our guy, but we have one problem. This guy, he looks a little bit warm to be standing in front of this kind of bluish toned window. So, why don't we do some color correction? I'll select delta keyer, and click on color corrector. And what this will be doing is correcting just our guy after he's been keyed. I don't wanna do this before our key, or else that's going to mess up the green selection, right? So, we're just going to color correct this specific thing. And I'll just take it a little bit more blue. Something like that. That looks pretty good. One other thing you want to do when you're color correcting something that has transparency, is in the color corrector node, go up to options, and make sure to click pre-divide/post-multiply. And that will just fix a lot of problems that can happen sometimes when you have a transparency channel. Okay? So, now we have this guy kind of neutralized a little bit more, his skin isn't so warm, we can kind of cool it down and match that lighting a little bit. So, there's our guy in front of the windows, and it looks a lot more realistic now that we've keyed out the green. And we've also added a little bit of color correction to kind of match those two layers. So, that's essentially how you would do a green screen inside a Fusion. Again, there's a lot more to learn, but those are the basics.