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We are back in Cinema 4D and if you've downloaded the project files and sources that came with this training, go Open, make sure you are in the Chapter 5 folder/Cinema 4D/room_5_starter and Open. Here I have created a different room just to keep things a bit more interesting. I have got a floor, a wall, a window that's juts out slightly from that wall, I'll give a quick render here. Why that's important is that if shadow was being cast against this wall, it would appear a little bit differently on this window than it would on the back wall, so a little bit more of an advanced case.
In our previous examples, we have been mapping video onto walls. Well in this case, we need to map our shadow catcher layers onto these walls. So just like the video wall case, we need to setup External Composting tags for these three surfaces. One thing we need to know is how big they are. So let's start with the floor. Here is my floor object. I need to figure out how big it is so I need how big of a layer to put on it in After Effects. So I am going to select my top of floor layer and note there's 3096 wall units by 2048, so that gives me its size.
I select my floor, apply a Tag>Cinema 4D>External Compositing. This gives me either a null object, or in newer versions of Cinema, a Solid that's placed right in the middle of that floor and fortunately, I already have my axis arrows placed square in the middle of the floor, right on the top of the floor. I need my shadow catchers to be white. So I am going to change these solids to be white in color, or you can replace them with a white solid in After Effects and what I'd love to do is type in the size of my floor straight here in Cinema.
The problem with that is Cinema currently restricts these solids to be no larger than 1000 pixels on a side. So unfortunately, I just need to make them 1000 x 1000 here in Cinema, then what I get into After Effects, I will go ahead and expand them out to the right size. But I've already written down somewhere what size this needs to be, 3096 x 2048. Let's pick my next object, the back wall. Again, I need my axis arrows to be flushed with the face of that wall because we want the shadows cast flush onto that wall.
I want to figure out how big that back wall is. I am going to click on back wall, note that it's 3096 wide by 1024 tall, good. I will select my back wall again and apply Tags>Cinema Tags>External Compositing. I will make it a Solid again. I will make it white since shadow catchers need to be white, and again, I'd love to make it the size of that wall, but I have to settle for just 1000x1000, as of Cinema in version 11.5. Finally, I want to create a separate little shadow catcher just for where that window is.
So to do that, I select my window boolean. That's how I created this window in the first place. I want to check its size, so I see the window main was 448 x 384, good to know. Select that window, make sure my axis arrows are flush with the face of that window. It looks like it is except for taking that bevel into account, so I will make sure I've got my Axis Move tool here and I will move it until it's just flush with the face of that window. That's good.
Select it. Tags>Cinema Tags>External Compositing, make it a Solid, make it white in color. This time, I can actually type in the numbers, and rather than typing in exactly the size of the window, it's good to have a couple of extra pixels left over because I am going to trim them with object buffers. We will get to that in a second. I am going to type in something like, say, 452 wide, just to give myself a little extra and 390 tall, so my solids a little bit bigger than this window. For this window, I really need to think about my Tag Properties.
For one thing, it was created as a boolean, one cube was cut out of another cube. I don't want the cache calculated in that point because otherwise, I am going to get solids for all these components that made up that boolean and I don't want that in this case. I am going to settle, in this case, making a solid just for the face of this window and use that as a Shadow Catcher, but if I was really trying to get the last little bit out of my composite, I would want a solid for every facet of that window, so I can catch shadows in all those different dimensions.
If you are working on a critical project, that's what you would want to do. Okay. You could just have these white solids for the back wall, for the floor and for the window. But the problem is is we do have some cut outs, some holes where shadows should not appear. Whenever we have cut-outs or we need to worry about trimming a layer, that's when we want to use object buffers. So let's go back to these guys again. I'll select my floor, and this time I will add a Tag>CinemaTag>Compositing, not External Compositing. I will go to my Object Buffer and make sure that I have assigned one Buffer, a unique buffer, to mask out just where that floor is visible in the final render.
I will go to my back wall, apply a Tag>Cinema Tag>Compositing. Underneath Attributes>Object Buffer, I am going to turn on another Buffer with a different number to create a unique matte pass just for that back wall. And finally, I am going to go to my window boolean just this window object here in the middle, and again apply Tag> Cinema Tag>Compositing, Attributes>Object Buffer. This time, Enable Buffer 3.
So I have a third unique matte pass that shows me just where this window is visible in the final composite. Now that I have got those, I need to go to my Render Settings, enable Multi-Pass, add some Object Buffers, Buffer 1, Buffer 2, make sure I increment the number to number 2, and Buffer 3 and increment, finally, to Buffer 3. I will go back to my Save, make sure I save these to a path that is actually on this computer.
I see that I am in my Chapter 5 folder, so I am going to create a New Folder inside for my renders called shadow catcher renders, Create, Save and do the same for my Multi-Pass. Make sure it goes in that same folder. I've got my Compositing Project File turned on to Save, After Effects and Include 3D Data. And now that I have got all that set up, let's go ahead and render it. Now you see that I am getting not only my Background render for the entire wall, but individual Object Buffers, a floor, for the back wall, without the window, and for the window itself. Pretty good.
Well this is going to take a while to render, so I am not going to make you sit here and wait. When this is done, we will jump into After Effects and see how we need to build our Shadow Catchers as part of that scene.
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