How to create expression

Hi guys, this is Eric from www.FinalCutStudioSchool.com and we’re going to delve a little deeper into shake this time and I'm going to show an example of some basic expressions and how expressions work.

Now I'm not going to be able to explain a lot of this but I want to give you an example of how expressions work and why they’re so powerful. As you can see here, I’ve added a regular color wheel node and I moved 2D node. I'm going to in to my move 2D parameters and open up my pan. I'm going to go into xPan and in my little box here I want an intermittent expression. I'm going to put sin(time) and hit enter.

The first thing that you’ll notice is this (+) comes up which means you have an expression in there. I'm not sure if you can tell this on YouTube but now that added that expression in the xPan when I move my play head you can see the little jiggle. I'm not sure if you do a whole lot of Key framing but in order to key frame this it would take a lot of key frames to add that jiggle back and forth without a pre baked behavior if you’re just doing it by manually key frame on it. This can save you a lot of trouble wit h that simple expression.

We can just say time and as you can say all that’s going to do is slowly move over time, over the cursor no matter how long I’ll hold it and scroll it to the frames. Even if I‘ll go to the frame a thousand it will keep moving over time because that’s all I got in there is time.

I can also add some basic math functions to it, I can say time*4. Now, you can just doing the exact same movement only x4 a lot faster and I can step to the key frames. It's the same if you’re having to key frame this it's actually wonderful. It increases the flexibility so much. Let's say you only wanted this to start moving after frame 10, you want it to stay right where it's at and in frame 10 you want it to stop moving. We would put time<10?0 and now it wont do a thing. I'm scrolling up on frame 5, 6, 7, 8, 9 and hit frame 10 it starts doing this thing.

We can enter on noise expression by typing noise(time)*5/50, I’ve added in some random noise. It's kind of just going around randomly back and forth in the xPan. Now that we’re full in the xPan, I can copy this by highlighting it, command C, go to my yPan, paste it and hit enter now I have the same expression on both x and y . When I scroll through, I’m going to get random noise, up, down and left to right.

Let's reset all of our values and go back to xPan and we’ll start over. This time we’ll use a sin wave, that’s (sin(time)*200)+400. Now, we have some massive movement going on that’s because I added a sin wave. If I'm going to go and look at my curve editor, you can see my sin wave. This is the expression, as I scroll through up and down; back and forth, the curve wave goes back and forth.

When I put sin at the front that means it's a sin wave. If I put noise, I’ll type in noise(time)*10 and I guess its a little bit randomness in the eft to right xPan. Let's add something to that, (noise(time)*100)*(rnd(time)*100) and we have some massive movement. I'm going to look it in my curve editor and you can see my random noise is generated and as I go through it's just this random noise I the xPan. As I’ve said, I can copy and paste this and go to my yPan then paste it. I want to change the number to (noise(time)*100)*(rnd(time)*200, it’ll also show this sin wave. Now you can see both of them I can turn them off by checking my clock and we have a random noise in my xPan and yPan, and that up there is going wacky whizmo ones, all kind of random noise.

That’s basically the basics of expressions. You got your sin, noise and we look it in our curve editor you can see just a steady incline. There are all kinds of stuff and I’d like to get into more expression but it's really hard to explain the math behind it over a screen captured on YouTube. I just want to give you the sin, cosine and the time. If you’ve seen some of the expressions that I’ve inputted, for the numbers input some different numbers in and input different expressions.

Let's try one more, (sin(time)*200)+400 and look at the sin waves on this one. You could hardly see it all, let me just go back and see what it's doing to our color wheel. It's going really wild back and forth. It's such a huge cosine that we’re not able to see it all.

That’s the basics of expression, play with it, fiddle with it and see what you can come up with; If you have any questions, I’ll try to help you with the best that I can.