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Using the Compositing tag and creating object buffers

From: CINEMA 4D Essentials 5: Rendering and Compositing

Video: Using the Compositing tag and creating object buffers

This is the image that we're going to be creating based on our original CINEMA 4D render. And this is the original rendering, and this is the revised rendering. What allowed me to change the color of the type without affecting the cubes is something called an object buffer. An object buffer is simply an alpha channel for an object within your CINEMA 4D scene. It's different than an alpha channel for the entire scene, it's an alpha channel just for a single object. Here in the project window, we've got a Special Passes folder.

Using the Compositing tag and creating object buffers

This is the image that we're going to be creating based on our original CINEMA 4D render. And this is the original rendering, and this is the revised rendering. What allowed me to change the color of the type without affecting the cubes is something called an object buffer. An object buffer is simply an alpha channel for an object within your CINEMA 4D scene. It's different than an alpha channel for the entire scene, it's an alpha channel just for a single object. Here in the project window, we've got a Special Passes folder.

This was generated when we imported our CINEMA 4D file from our Renders folder. I'm going to double-click on workflow_object_3, and this is the object buffer for the type. You could see that it's just a black and white matte that only highlights the type, and this allows me to control the color of the type. The process for making this matte is pretty straightforward. It involves something called the Compositing tag. The Compositing tag is the most powerful tag in all of CINEMA 4D; it's the most important in my opinion.

It allows you to do dramatic things with your rendering process. Let's move over to CINEMA 4D. So this is our scene file in CINEMA 4D, Compositing-Tag-START. Here's my type element. What I want to be able to do is to have an object buffer for that type element. So what I'm going to do is right-click on the Extrude NURBS that represents the word Compositing and go to CINEMA 4D Tags, and then Composting tag. Now this gives me this little tag that looks like a clapboard. On that tag is a property called object buffer.

I'm going to activate object buffer number 3. Now I could put any number that I wanted in here. I can make this 3,000 or 27; it doesn't matter. The important thing is that the object buffer is a two-stage process. We have to have a number here that matches a number in our render settings. We're going to make that number in the render settings in just a moment. First, we're going to set our numbers here, and then once we've got them all set, we'll confirm those numbers in the render settings. So now, I want to have workflow in the exact same object buffer. So rather than go through the whole process of right-clicking again, I can just hold down the Ctrl key and drag a copy of the Compositing tag down onto the word Workflow.

So now I have the exact same Object Buffer settings for these two words, just what I want. Now let's do an Option+R or Alt+R on the PC, and bring up our interactive render region, and let's enlarge it just a bit. Now if your Quality setting is set to halfway, go ahead and raise that up to full quality there. That's that little triangle there. I'm going to bring that down so I can see the entire frame. You'll notice that when I render, I can't actually see my type, that's because of this disc.

There's a disc in the scene, and I'll uncheck the Visible in Editor dot in order to see the whole thing. This disc is causing a highlight on the surface of my type. You can actually see that right here in the reflection on the type. I call this a highlight disc. It's a common technique in motion graphics. These discs are used all over the place to generate little highlights on the surfaces of your type. I don't want this highlight disc to be visible on the rendering. The Visible in Editor and Visible in Render buttons only go so far. I can hide this disc here in the Editor window by making this top dot red.

I'll click twice on that. This bottom button though, if I were to double- click on that, that would make my disc not visible in the rendering either. Watch, I'll double-click, and make it red and you can see that my disc goes away. That defeats the purpose of having the disc there. So what I want to do is to create a situation where the disc shows up in the surface of the compositing workflow but does not show up in the type itself. It also shouldn't show up in the floor. So I need a Compositing tag for that. So let's first off make the bottom dot gray again, so that the disc shows up.

Then we'll right-click on the disc, and go to CINEMA 4D tags > Compositing. The Compositing tag is incredibly versatile. There are a lot of settings in it. Underneath the tag properties for that, we're going to turn off Cast and Receive Shadows, we're going to turn off Seen by AO, that's Ambient Occlusion, and then we're going to uncheck Seen by Camera. When we do that, watch what happens. Now you can see that the disc shows up in the surface of my type, but it's not visible in the rendering. That's really important.

I'm going to uncheck the Active Camera icon, and let's take a look at the scene from a different angle. One of the things that happens as we move through, let's go right here. You'll see that the disc is also visible in the floor; when this gets done redrawing, you'll see that I can see my disc in the floor, and I don't want that, that's this blue gradient right here. The Compositing tag has another very important option called Exclusion. If I go to the Exclusion option, there is an Exclude pulldown here; it says Include or Exclude. I want to leave it on Exclude.

What I want to do is tell this disc to not affect the reflections of the floor. So if I take the floor object and drag it in here, watch what happens to this area of the rendering as it finishes. You can see that the disc no longer shows up in the floor. That's a really important option. Let's go back, and look through the camera. Click on the Active Camera icon. Now you notice that right here at the bottom of the type, that little dark spot right there is a reflection from the cubes showing up in the surface of the type.

So I don't want the cubes to show up on the surface of the type either. So what we need to do is to add a Compositing tag on the Hero Cube to have it not show up in the main type. So let's right-click on the Hero Cube and go to CINEMA 4D tags, add a Compositing tag. And in the Compositing tag, under the Exclusion option, I'm going to say don't affect Compositing, and don't affect Workflow. And you notice that got rid of a little bit of it, but it looks like I've also got these main cubes as well to deal with.

So what I'm going to do is right-click on this null here. This null is the null that holds all the other cubes in the scene. Let's right-click on that and go to CINEMA 4D tags and then do another Compositing tag. So let's add a Compositing tag. Now in the Exclude options, let's drag in Workflow and drag in Compositing again. And watch what happens, that's going to clean up the face of our type. There we go! You see we no longer have that black splotch down there. That was based on the reflection probably from this cube right here.

Next step, we want to make sure and set object buffers for the other important elements in the scene. Now I know that I may at some point I want to add a glow to this cube or just do something to it, change the color, who knows. So I'm going to add an object buffer to this. A lot of times when I add object buffers, I may not end up using them, they're just preventive measures. It's much better to have an object buffer and not use it than need an object buffer, and not have it. So I'll often times set an object buffer even if I am not sure if I'm going to need it or not. So on this Hero Cube, let's make that object buffer number 1.

And then I'm going to go to the main cubes, and set that object buffer to be number 2. So object buffer 1 is the Hero Cube, Object Buffer number 2 is the rest of the cubes, object buffer number 3 is the type. So we've got our object buffers and we've got our Compositing tags all set up. Now what we need to do is to make sure that we have those object buffers covered in the Render Settings. Let's hit Command+B or Ctrl+B on the keyboard to bring up the Render Settings. And my Render Settings are pretty basic right now.

All I have done is set the Aspect Ratio of the scene, so I know that I'm going to need to render from 0 to 89. So let's go and render from 0 to 89 for my Frame Range. Now what we need to do is to activate Multi-Pass. So let's activate Multi-Pass and then in the Multi-Pass options, let's click on that, and go to Object Buffer, and we'll add that three times. There is number 2 and there is number 3. Unfortunately, the object buffers will always be numbered. Uou cannot name your object buffers, but what you can do is name them here in the render settings so that you at least have a reference for what they are.

So let's first start off by highlighting each of these. I'll click on the first object buffer, hold down the Shift key, and click on the last object buffer. That brings up all of their IDs at the same time. Now I can go through and name 1 number 2, name 1 number 3. The only thing that links them back to the object buffers is this number. This number links it to the Compositing tag that's over here. As long as the numbers over here, match some numbers over here, then you're going to get something in your object buffer. It's very important that these numbers match. Now what I'm going to do is to name my object buffers.

So object buffer number 1 which is this guy, we're going to call it 1 and Hero Cube. I'll use the down arrow and call this next one 2 Other Cubes. Let's call this last one 3 Type. So that is the basic object buffer setup. So we first set object buffers to eliminate any sorts of odd reflections, then we set up our object buffers for the main elements in our scene.

Sometimes you set up object buffers for things you know you're going to need, sometimes you set up object buffers for things you might need. Then once we had our object buffer Compositing tag set up, we went to the render settings and made object buffer settings for each one of the numbers that we used in the Compositing tags. Those are the most important steps for setting up the Compositing tag. The next most important tag in CINEMA 4D for working with compositing programs is called the External Compositing tag. We'll take a look at that in the next movie.

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CINEMA 4D Essentials 5: Rendering and Compositing

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Rob Garrott
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