Creating a pre-render

Now believe it or not, I have a bunch of friends that kind of make fun of me for doing this technique, but honestly, I really kind of enjoy pre-rendering. So if you're an old-school designer, you probably know exactly what I am talking about, but if you've always been in the world of real-time motion graphics with Motion, you may not completely grasp the advantage of pre-rendering something. So let me take you through a typical workflow that I would do when I know I'm going to be creating a rather complex animation. So let's look at our project here and as you can see, we have a video layer with the Keyer attached to it.

Now we definitely went over how to create this in the Green Screen chapter, so I am not going to jump into the Keyer options and things like that. I just want us to look at the playback here by pressing the spacebar on our computer, and you notice immediately that it's going to play back rather slowly. That's because Keying is somewhat processor intensive. Now I know this key is a little rough, but that's perfectly fine because the treatment that I want to do, I am going to change her into a silhouette, and then I want to replicate that silhouette all over the place.

Let's think about the processing that's going on right now. See, I have got the green-screen footage, which if we zoom out here--I will Command+Minus--you notice it is larger than our project. So let's go to the Inspector with that piece of footage selected and in the Properties section change the Scale down to 67%. That way as she dances around, she's not getting cut off on the edges and then she really moves out of the scene. Now this process of just choosing the green-screen color and keying out the background is pretty intensive.

Now we're also scaling the image down as well. The second we try and load this into the replicator, imagine what's going to happen. You're going to have, I don't know, twelve copies of this or sixteen copies of this, and each time, yes, it loads the keying once, but it has to replicate that multiple times. So as you would imagine, this can be very processor intensive. To make the work a lot faster, one of the things I like to do is just pre-render something if I know that I'm going to be using it for a specific task.

I like how her T-shirt is cut out of the background because of the style it's going to create. So select the QuickTime file and let's go to the Library and in the Filter section I want to go to Color Correction. See what we are going to do is change her into a silhouette. So grab the Colorize filter and just drag it and drop it right on top of her QuickTime layer. And in the Inspector, let's remap black back to black and we will remap white all the way to black, and now we're getting that kind of famous silhouette look.

If I press the spacebar here, you'll see the playback is a little slow and I do have a little bit of degradation that's going on within our dancer, and that's just because the black and white values aren't quite covering absolutely everything the same. If we go to the Inspector under Remap Black and Remap White, you can just make doubly sure that that's 100% black when we make that adjustment, same thing here with the white. Okay, so now that we have got our silhouette set up, now it's time to actually export this.

Now in the past, if I had to go to Share right now and say Export Movie, it would export of this black silhouette and the red background married together. Now the old way to fix this is to deselect the background and then go up under Share and export the movie. But there's a faster way to do this and if you have many, many layers underneath of something that you've keyed and you just want to export the one keyed layer, all you have to do is select that one layer and then go up under Share and choose Export Selection to Movie.

See, when I do this, it's automatically going to only export that one layer. Now I know it doesn't look like that based on the thumbnail, but it will. So let's look at some of the options for this. Under the Export options, yes, I want to export ProRes 4x4, because in the Render settings I do want to export my Color channel plus the alpha, which is the transparency of the image. Now for the Render Quality, instead of using the Canvas settings, I am going to set that to Best, and in this one instance I don't want to enable Motion Blur.

Now I can continue going through and showing you all the different options, but this is the look we are going for. So all we have to do is click Next, and now we can pre-render this element. If you go into your exercise files folder, in the Media folder there is a folder for Footage. In there we have an option for Exported_Sources. So when I click on that, you will see I have my KeyedDancer video file that I already output earlier. Now just so you can see exactly what happens when I do hit the button, I'll go ahead and just add a 2 at the end of KeyedDancer here and click Save.

Now what's going to happen? It will render the dancer, key it off of the background with an alpha channel, and then open that QuickTime and show us exactly what's going on. So notice when I open the QuickTime, even if I press Play, not really seeing anything. That's because it did output the transparency data and since all I had was her filled with black, we are not seeing anything. What we need to do is actually view the alpha channel. So to do that, I'll just collapse my two layers and turn off their visibility.

And if we go to the File Browser, let's navigate in our exercise files folder, in the Media folder under Footage, there is an option for Exported_Sources, and here's our version 2. Notice I get a preview right up here in the File Browser. If you want to see it in your project, just drag and drop it right into the project. Now, as I'm looking at this, I still can't see this, so you may have to come to this color window up here in the upper right and change it from Color to Alpha Overlay, or change it just to straight Alpha.

That way you can see exactly what's going to actually be transparent and what's going to be filled in. Now there is one last setting you should pay attention to when you go to export your movie as a pre-render, and that's the actual size of the movie. See, if I knew I was only going to make our dancer 50 pixels high and make duplicate copies of her, I would just make a QuickTime that's only 50 pixels high, and then I would just use that as the source for my replicator.

By not including all those extra pixels to making her large, I'm just making the pre-rendering that much more efficient, and that will make the replication that much more efficient. So the easiest way to think about pre-rendering, anytime you think you're going to be building a project that might look like it's going to actually bog down your system, you may want to look at the individual elements to see exactly which ones you'd like to pre-render.