Design smooth, organic animation paths in After Effects using RotoBezier and trace path techniques. This article guides you through setting up a null object to follow a custom path, enabling dynamic motion control for elements like a rocket ship.
Key Insights
- RotoBezier allows users to quickly generate smooth, curved paths from straight-line inputs without using bezier handles, making path adjustments more intuitive.
- The trace path feature converts a shape path into a motion path for a null object, enabling dynamic animations that update live when the original path is adjusted.
- Noble Desktop's training covers how to use null tracing, effect properties like "Progress" and "Loop," and customizing preview settings to visualize path-following animation in real time.
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So for this lesson, we'll be creating realistic or organic motion in another fashion. We're actually going to use the program's ability to create nulls that follow a path, a shape path, and then we're going to basically parent the rocket ship to that. So the first thing I got to do is create a path.
So I'm gonna take my pin tool and I'm gonna do this the easy way. I'm gonna turn on the option, which basically automatically makes smooth curving paths. That's the goal of it, actually.
So I don't need to fill this out, so I'll click on fill and disable it. But I am going to have a stroke and I'll leave two pixels. That's fine, basically.
I'll just choose where to start. I'll start over here, I think, actually. And I'll just click.
And this is what RotoBezier does. It basically gives you a smooth curving path by making straight lines. So I'm just clicking around.
It's auto-curving it for me. I can adjust these points so it's not a problem later. If I don't exactly do it properly, not a problem.
I'll end up right there. We'll start pulling around with the selection tool feature of the pin tool. Notice as I do that, they're auto-smoothing.
This feature is designed to provide me with curving paths. So RotoBezier is pretty nice about that. If you don't want to use RotoBezier, that's not a problem.
If you're familiar with how to make smooth paths using the regular pin tool, just disable that feature. And then you can use it just like the pin tool and like Photoshop, Illustrator, that sort of thing. So I'm going to make a few more adjustments to this to smooth it off a little bit.
Like so. And that's the result of RotoBezier. So I can make curving paths.
Let's start with straight lines. And the program basically auto-smooths it for me. That's all it is.
So it's pretty cool. Works out pretty well, if you notice. Like that.
And unlike with the bezier paths, it doesn't have handles. So again, adjusting it is simply a matter of changing the position of each point. So like that.
Okay. Okay. So I've got the path, and now I need to actually find what I'm looking for.
So I'm just going to rename this path. I'll call it motion path, by the way. I'm going to locate that, the path.
I'm just going to double-click on it right here. In the properties panel, when you double click on the shape property path, or technically, for that matter, we can double click on anything, its property reveals in the timeline. That's what I'm looking for.
This is what it's going to use. I'm going to right-click on it. I'm going to key from the assistant and null controllers for path points.
Null tracing. Nulls follow path points. I want null tracing along the path.
That's what I'm looking for. What this will do is create a new layer. A null.
Hello null. I'll change its color from purple to something brighter. Maybe yellow is a good choice in this case.
You can see it easily. I'm going to press A to reveal its anchor point. This is simply a personal thing I like.
I prefer when the anchor point is in the middle of the layer, not in the corner. So 50 50, because nulls are always made to be 100 pixels wide. I just like that a little better.
Now, as I drag through it, it's following the path. Now, for the record, if the path itself does change, because I can change the path with my selection tool, then what the null is following will also change. Notice right here, the null will simply update.
The null layer, no problem at all. This is actually a live effect. The other thing is that it actually automatically loops, and it gives you one second of animation by default.
So I'm going to open up that null layer. Trace motion paths is what it's called, by the way. I'm going to call it following null.
You can call it Bob, for all it cares. And in transform is a position run by an expression. Rotations run by expression.
But if I close that, I look at the effects. It's an effect called trace path. This is actually what the command did.
Progress is the length of it along the line. So 0% at the beginning, 100% at the end. And the fact that it loops is an option.
So loop on disable loop for that. I would like to slow down this motion, so I'll just give myself five seconds of motion. I'll just drag that second progress keyframe out to five seconds, and it'll hold shift as I drag, it'll snap.
So now it's moving much more slowly. I can't actually see that because the null doesn't display when you preview. But if I go to the preview panel options, I can turn on this third button right with include.
And now, when the path is selected and I preview my timeline with spacebar, I'll see the null move as well. So nulls automatically hide in general when you preview, but with this option, you can enable them. And that's what's happening with the null.