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My render in Cinema 4D is done. I am back in After Effects with a new project. I am going to do Command+I on Mac, Ctrl+I on Windows to import. I'm going to select the folder for my shadow catcher renders. You'll see, again, Cinema has created a .aec file for me, my backgrounds and my three object buffers for my shadow catchers. So I will go ahead and select aec and Open. Once I bring this into After Effects, we'll look at our composition, I'll deselect and you'll see, in addition to my 3D render, I have solids for my floor, my back wall and for my window cutout.
Here is the render just as seen unmolested. The lights are animating a little bit in the scene, in addition to the camera moving, and we'll verify that by selecting the camera, these different lights, pressing U to reveal their keyframes and you can see the motion going on, the camera eases to hold at five seconds, while the lights keep drifting. And finally, our Special Pass renders, our three object buffers, the floor, the back wall, minus the window, and finally, the window by itself.
Let's go to the scene and start setting it up and this is going to take a little work, but we're going to do everything three times for our three surfaces. First, let's make those three solids the correct orientation and the correct size. Now, for some reason, Cinema brings in that solid facing straight forward. It doesn't realize it's supposed to be laying flat on the floor, but that's okay. I see it's my red or my X arrow that I need to rotate it along. That's the axis I want to flip it on. So, I'll type R for rotation and orient it 90 degrees so that it lays flat along the floor.
Next, I need to change its size, underneath Layer>Solid Settings. I know that this floor is 3096 pixels wide. I like to have a few extra pixels on the edges to trim off, just to keep things nice and clean. I'm going to make it 3100 wide. For the Height, I know it's 2048 in Cinema. Again, I'll just round it up to 2050, click OK. Now I have a surface that covers the entire floor. Next is the back wall. Twirl up the floor, select the back wall, again, choose Layer>Solid Settings, the shortcut is Command+Shift+Y on Mac, Ctrl+Shift+Y on Windows, and change its size.
Again, its 3096 wide, I'll round that up. It's 1024 tall and I'll round that up to, say, 1028. Now, I have something covering the entire back wall. And the Window Boolean was already the correct size, so there is no need for me to do anything further with that. The next thing I want to do is trim those shadow catchers, so that they exactly confirm to the surfaces they are sitting in for. So in the case of the floor, I'll pick my shadow catcher 1, this render that matches the floor, drag it just above the floor, hit F4 to open up the modes panel and say use that as a luma matte and there is the floor trimmed.
I'll pick up my shadow buffer number 2, drop in front of the back wall, set the back wall to luma matte and it will matte that out. And finally, I am going to grab my third buffer, drag it above my window, set it to luma matte as well, and now I've got that cut out as well. Okay, so I have these three solids, each sitting in for my surfaces in a very rough fashion. Before we really see how to make these shadows work, I need to create something that casts the shadow. So I am going to select my Text tool, have a nice bold font, such as Arial Black, I'll pick a color such as some sort of medium gray so you can see what it looks like.
I have a nice big font size picked already. Let's just start typing, such as shadows: catch me. Press Enter, then press V to return to the Selection tool. I need to go back to Switches down here in the timeline, so I'll press F4, but I need to enable the 3D layer switch for my text. I do so and it kind of defaults down in the floor. Let's go ahead and pull it up out of the floor, push it back a little bit, pull it over a little bit and pull it up a little bit.
Again, layers in After Effects do not cast shadows by default, so I need to select it, type aa to reveal its Material Options and turn on Casts Shadows. The shortcut is Option+Shift+C on Mac, Alt+Shift+C on Windows. So now, my text is casting shadows. I see a bit of this shadow down here on the floor, but the wall has this very strange look about it. Well, this is because these solids are catching lights and catching shadows. We want our shadow catchers to only capture shadows, not light.
The light's already been factored into the 3D render. It's only the shadows we want to add. So to do that, I am going to start with my floor, select it, type aa to reveal its options. Keep on Accepts Shadows, but turn off Accepts Lights. That way, it is just a 100% white solid and if you forgot to make your solids white, just go ahead and change your color in Solid Settings, and that has captured my nice black shadow. We'll do the same to the back wall, aa, Accepts Lights off.
Now I see black shadows. And for the window, aa, Accepts Lights off. So again, this is very important, Accepts Shadows on, Accepts Lights off. That's one of the main secrets to this trick. Okay, I now have black shadows on white walls, but what I really want to see are my original walls underneath. Well, this is where blending modes come back to rescue again. Remember when we did multi-pass renders that Cinema put the Shadow layer in Multiply mode so the white was unaffected, and only the dark areas were darkened on the render? Well, we want to do the same thing here.
Once again, press F4 to return to our modes and now for the Window Boolean, I will set its mode to Multiply. Now, the window comes through as just the shadow. Go to the back wall, same thing, Multiply mode. There is the back wall with its original rendered color but with my shadows added in. Finally, floor, set it to Multiply mode as well, and there is the floor with just the shadow from the text.
And to show you that this is interactive, I am going to pull the text around and you'll see how as I pull it closer to the lights, the shadows grow in size and also travel across the floor. As I drag it up over this window, you'll notice how the shadows do, indeed, break up across this window. They are falling on the front surface of that window separately than they are falling on the back wall. So, that's another important trick. We have a little bit of artifacting here on the edge, but frankly, that's a lot better than no shadows at all.
Well, by the way, speaking of artifacts, sometimes when you do this sort of trick with object buffers, if you render this with an Alpha Channel, you might see a white fringe in here, in an interface between the Alpha Channel and the object buffer. If you ever see that white fringe, select the object buffer layer, not the shadow catch layer, but the object buffer, that's causing you some grief and giving a white fringe, and apply the Minimax effect to it, Minimax.
Apply it to your object buffer, set it to Minimum rather than Maximum, set it to a small Radius of 1 and that will clean up any white fringes you see on the inside. It does have the cost though of shrinking your shadow catcher and also creating a bit of an edge here right around this fall off. So only use it if you see an artifact.
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