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One area of potential confusion with mocha is how it handles motion blur in combination with After Effects. Because the way it does in with motion tracking data is different than the way it does it with shape d ata. Now here is an example we played around earlier where I tracked a section of this wall and wanted to put something fresh on that wall in After Effects and of course, tried to match the motion blur the best I could. To do that, I selected my layer with a tracking data, did export, and this menu is going to change probably in the final shipping version but basically I picked the version that said After Effects Corner Pin supports motion blur.
This adds positional data in addition to the corner pin data to allow me to get motion blur in After Effects. And there are other options if you're using Red Giant's Warp plug-in, if you are using the excellent mochaImport script but I've got just bare bones After Effects. So I'll select that, copy to clipboard, and you already saw back in After Effects that if I wanted motion blur on my special graffiti that I've added to this wall, [00:01:04.9 5] a little brown shape back there, I just need to enable motion blur for that layer. There is the sharp original shot.
It doesn't looks very realistic when the things are flying by. There it is with motion blur enabled. It fits into the scene much better. That's what to do for tracking data. Shape data is different. Go back to mocha. If you've been watching the tutorials on Imagineer's webs ite, you might have seen that tutorial for the standalone version of mocha that has a dedicated Motion Blur parameter. Enabling this parameter allows it to render mattes which have blurred edges.
However, mocha with After Effects does not render mattes. Instead you export shape layers. So you don't pay any attention to that parameter. Instead you need to do a a bit of playing around with the shape data. So I going to take my shape here. Instead of making it a motion track, just for fun, let's use the shape data to create our track matte. I will export, Selected layer, copy to clipboard, switch to After Effects, get rid of my wall addition for now, don't need it. Pick my original shot, make sure my time indicator is back at the start of the clip or at least where I started my motion track, then paste, and now I've got mocha shape data just for that wall segment.
Now you might have noticed that it does not have blurred edges and even enabling motion blur for the layer with mocha shape is not going to add a blur to it. You need to do a trick and this is a universal trick which applies to anything you want to add motion blur to in After Effects, including footage that already rendered say from a 3D program. I will turn it off for now and I want pre-compose this layer. I want to have the shape data with its motion and its own pre-comp, so it looks like a fresh piece of footage to After Effects.
Layer > Pre-compose. I'll call it mocha shape percomp. I am going to move all attributes back, which mean to also move my mocha shape effect, and there is no need to open a new comp. I'll stay where I am. Click OK, there we go. Now to add a motion blur to any footage or pre-comp layer in After Effects, pick Effect > Time > Timewarp. We'll set just a couple of parameters here.
We've got o set the Speed to 100 or 100%. You need to Enable Motion Blur, so turn that on, and set the Shutter Control to Manual rather than Automatic. Now I can say, hey I have 180 degrees of of motion blur, a typical filmic motion blur for this layer, and now I've got motion blur on my shape layer. Before, after. V ery cool addition, particularly if I just had a white track matte here that I'm going to use to matte out another layer.
If I zoom in on this, look closely to these edges. You'll notice that there is some ghosting or stuttering at these edges. All you need to do is increase the Shutter Samples to make this look better. I recommend at least 8 samples and if that's not smooth enough, go all the way up to 16. And now you've got a really smooth edge. It takes longer to render but it's worth it. Just a give you an idea of what that looks like on normal matte, I'll select my Comp panel, tap Shift key, go back to the mocha precomp.
Let's just look at this as a color composite, as just that white shape. Tap Shift, go back to my original comp here, give it a moment to render, and there is my beautiful blurred matte. Without that motion blur trick, just sharp edge with the default number of samples, kind of stuttery, not a very good edge. Trading off some render time, maybe 12 samples.
Beautiful, smooth matte edge that I can now apply on top of other footage and blend it into my original seen. So that's how you add motion blur when you're working with mocha. But this trick with Timewarp, its universal. You can use in other things, such as 3D renders that don't have motion blur.
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