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Skill Level Intermediate
- [Steve] Hi, this is Steve Wright, welcoming you to this week's Nuke Nuggets, a close look at the Roto Node Feather falloff control. The Roto Node gives you tremendous control over the lick of the feathered edges of a Roto. Here we'll take an inside look at the four falloff types and the falloff slider to see what the various feathers look like and their final effect on the edges of your comp. I'll select my shape here to light up falloff type. Now we're talking about the four falloff types right here.
By default, we'll look at the first one which is linear. I set up a sampler node so that I can show you, sample, exactly what the falloff looks like, and of course the linear falloff is perfectly linear. This up here is the edge of my shape. Then the falloff is linear until we get to the edge of the feather. So the edge of the feather's down here, the edge of the shape is up there. Now the linear gives you a hard edge at both the shape and the feather.
So we look in the viewer, we're looking at the alpha channel, we can see here this is my feather edge and it's sharp like the curve indicates. I don't really see a problem with the shape edge until I drop the viewer gamma down, oh, there we go, look at that. So that reflects this shape edge here. Now if we look at a comp, we can see we have a nasty hard edge at the feather edge and you can see a bit of a hard edge here. if I gamma down the viewer, you can see it really clear.
So that's your linear. Now we'll come back and look at the feather falloff slider in just a minute. Next, let's take a look at the smooth zero. OK, we'll sample that, and look what we've done. We've picked up a false edge down here at the feather edge, but I still have a hard edge for the shape. If we look at the alpha channel, we can now see the soft edge and I can compare it to the original linear hard edge, there it is, but we still have the hard edge at the shape.
So I'll viewer gamma down, boom, nasty hard edge, nasty hard edge. OK, viewer gamma up, and we look at the comp, we can see that the feather edge is nice and smooth, but again, our shape edge is showing up in the comp. OK, let's take a look at smooth one, and we'll sample that. So what's happening here is I get a smooth edge here at the shape, but a hard edge down at the feather edge. If we look over here at the alpha channel, we can see again hard edge at the feather, smooth, even if I gamma down the viewer, my shape edge is nice and smooth.
And if we look at the comp, we'll see the same thing, nasty hard edge here at the feather, nice smooth at the edge of the shape. Last we'll take a look at the smooth and see what that does. Aha, we have an ess curve now. I have a smooth edge here at the feather edge as well as up here at the shape edge. So this is the prettiest of all. If we look at the alpha channel, we see my feather edge is smooth, and viewer gamma down, the shape edge is smooth.
Looking at the comp, everybody is smooth. OK, let's go back and look at the feather falloff slider right here. I'm going to set this back to linear and resample. Now it didn't update, what's going on? Is my Nuke broken? No, this is just the cache. Nuke remembers that I've already seen this picture, so it's not bothering to update the sampler. Well, we'll just go up here to the cache and say clear all the cache and click sample current frame one more time.
Click, there we go. So if you're trying this at home and your sampler node doesn't update, clear the cache. OK, so let's look at the effect of the feather falloff slider on the linear one. Let's raise the feather up. Now, by the way, watch over here. You can see the effect visually. Feather up and let's resample. There you go, that introduced a nice soft edge on the feather side, but a nasty sharp edge on the shape edge. And we'll go in the other direction, resample, I'll get a sharp edge at the feather edge and not such a sharp edge at the shape edge.
OK, let's put that back to default and resample, and we didn't get an update because we need to clear the cache. One more time, sample, here we go. OK, now let's look at tricking this thing up. I'm going to close this. You see what I've done, and I've got my Roto here and a color lookup node there, so let me open up my color lookup node. And let's pull the viewer over here so we can see what's going on.
So I'm starting off with a linear falloff. I'm going to choose the alpha channel curve, because that's where my shape is. Select both control points, right mouse pop up, set the two control points for horizontal, which gives me an ess curve. Now if I resample, I have an ess curve on my feather. In fact, you can see right over here how nice that looks. Let me toggle that on and off for you.
See that? Pretty, pretty, huh? The nice thing about doing this is I can play some games. I'll add a control point here and I'll increase the slope of my ess curve, and then we'll resample. Ooh, look at that. So with the color lookup node, I can literally sculpt the edges of my Rotos. And by the way, the same edge-sculpting technique will work for any of your keys as well. So there you have it. How the feather falloffs work, and their effect on your comp edges.
Be sure to check in next week, so you don't miss out on my next Nuke Nugget.