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Explore how to use the motion tracker and stabilizer built into After Effects and shows how to handle a variety of shots. Author Chris Meyer leads a quick tour of the third-party software mocha and demonstrates the workflow for The Foundry's KEYLIGHT, both bundled with After Effects. The course also covers tracking a greenscreen shot with a handheld camera and replacing its background.
The After Effects Apprentice videos on lynda.com were created by Trish and Chris Meyer and are designed to be used on their own and as a companion to their book After Effects Apprentice. We are honored to host these tutorials in the lynda.com Online Training Library®.
I want this text to integrate better with this scene. And one way to do that would be to have it cast shadows on the face of the building behind it. To do that, I need to have a layer attracts the face of this building that receives shadows from the text. So I'm going to select the 3D Camera Tracker effect apply it to my underlying footage, lasso together some more points here, average them together to create myself a good Track Point, make some more up there, move my target roughly where I need the Shadow Catcher to be centered -- the sun seems to be coming down at this angle - I could hold down Opt on Mac, Alt on Windows and resize it a bit, but I'm going to be doing a lot more precise sizing later on once I've created the Shadow Catcher.
Now that I have my target in place, I right-click and choose Create Shadow Catcher and Light. This means two layers will be created; one is my light from my scene and the other is this layer called Shadow Catcher. And indeed, you can now see a shadow appear in the scene. After Effects has done some work for me, in making sure it sets the parameters for my text Shadow Catcher and Light for all this to work. And I'll type AA to reveal 3D parameters. After Effects has already set Casts Shadows to be on.
And when the 3D Camera Tracker created my text, it also set Casts Shadows to be on. Normally 3D Layers default to cast shadows being turned off because that takes more rendering time. But the 3D Camera Tracker anticipates I may be creating a shadow catcher later on. So when it created a text layer, it turned the switch on ahead of time for me. Finally, the Shadow Catcher itself takes advantage of a really cool material option. Not only can you decide when or not to accept lights, you can decide when not to accept shadows.
And as of After Effects CS6 they added a new option. Before shadows used to be off or on, and before when you had Shadows on, you had to create a white Shadow Catcher, you had to turn off Accept Lights, you had to use a Blending Mode to blend the shadow in. Now After Effects has added a nice little parameter called Only, where the only thing that renders for that layer is the shadow it receives. Very nice touch. Control that up for now. I do have the light in my scene but my shadows aren't falling exactly the way that I want. So there's a couple of tweaks I need to do.
I'm going to select the Shadow Catcher Layer, type "R," zero out its Orientation, and then type "S" to get it to Scale. I need to scale and position the Shadow Catcher to only to be on the face of this building and not overlap this other building because any shadows that would fall on this building would not be the same as on the main building behind. I'm actually going to turn off the Constrain Proportion's lock so I can scale these independently and make these shadows just the size that I want. That's roughly the width that I want.
I'll use the Axis arrow, constrain to X and move it over. So it just carefully lines up between the edges of that building and the edge of this building. Double-check that over time, yeah, that'll be fine. And I don't need to worry about the Y dimension quite as much just making sure that it's high and low enough to catch all the shadow I might want to cast. Now the other thing I noticed is that my Shadow angle isn't quite right. This building is casting a shadow down and outward in this building but my shadow is currently going in the other direction.
Well, let's just switch to 4 Views here quickly. I'm going to hold the Spacebar to pan down so I can see my shadows, look at my top view make sure I can see all my layers, C for the Camera tool, right-click and drag just to pan back a little bit. I see that my light is indeed in the wrong place. It's off to the right. I need it off to the left. So I'll press V for the Selection tool and drag my light over until it's cast slightly to the right side just like the other shadows in the scene.
Maybe there, pick my front view, look at all my layers again, and move the light up. The lights below the building, in this case the sun is slightly above the building. I'm looking at these other buildings behind to see roughly how my shadow should be cast. That looks a bit better, attracts a little bit more nicely. I think I'm going to cheat my light a little bit more to the right though because I do want to illuminate the right side of my building slightly as well.
I want that shadow to wrap around a little bit just for fun. Okay, that looks better. Looks like my Shadow Catcher could come out very slightly taking in this entire edge, and finally my shadow is again a bit on the dark side. So I'll select my Light, type AA, and reduce its Shadow Darkness slightly so it's not an inky black shadow but it's something that matches the other building here a bit more closely. Somewhere around there, it looks nice. Okay, let's go back to 1 View. I'm going to press Shift and forward slash (Shift + /) to re-center my view make sure I'm doing everything at 100% so that it renders nice and crisp, and RAM preview.
Now that is kind of fun. I think I'm going to move my text just a little bit though. Select my Text, pull further away from the building and you'll see that the Shadow Perspective changes. Maybe drag it a little bit just to reduce chances as it collides with the other building like around there. Now you notice that my poster on the side here has gone dark. And the reason is, is that it reacts to the 3D Lights in the scene and they're kind of glancing office, they're not really fully illuminating it. I could add an Ambient Light or a Fill Light, but even easier would be to select my Poster Layer, type AA, and set it not to accept lights, just go ahead and keep its original color.
I'll copy that parameter and paste it on my copy to the poster below. So I have a nice shadow on the front of the building. If I wanted the shadow to wrap around the side of the building, I just need to create another Shadow Catcher for this side. And I'll do that quickly. Take my Camera Tracker, take my Track Points back. Lasso a bunch of points to average together to get that face, right-click, Create Shadow Catcher. Select it. Type "R". Remove its Orientation.
"S" turn off the Constraint Proportions lock. By the way, Scaling of your Shadow Catcher Layer does not affect your render quality. Well, good, that sizes up pretty well there. But I'm not really seeing much of a shadow so I think my light needs some repositioning. I'll go back to 4 Views, pick up my light and pull around the edge a little bit here so that the end falls across that side of the building. Go back to 1 View. Not sure I like that elongated end but it does help sell the scene a little bit better that the shadow is integrated into that scene.
Reduce my Shadow Darkness a little bit and maybe increase the intensity of the light to better illuminate my text. Now I am noticing one other problem I need to troubleshoot because I am still seeing some effect of shadows here on my poster. When you see that, you've got something going on so just a poster casting shadows onto the building. In other words, the poster is not at the same position in space as your Shadow Catcher is. And that can happen when you use different sets of data points to create new layers using the 3D Camera Tracker.
I'm going to look at the Shadow Catcher, press P for its Position, and I see it's at around 5823Z, and I'm going to look at my Null that I created earlier and see that it's actually a little bit offset in space at 5716. But when I created that Null I was really careful to select four points far apart and a bunch of points in the middle. When I created the Shadow Catcher I was considerably sloppier and just grabbed a handful of points. The Null probably has a more accurate track and more accurate position. So I'm going to take 5716, enter it for the Z position, the depth in this world, and now the Shadow Catcher and the Poster are on the same plain, I don't have any problem with ghosted shadows appearing in my scene.
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