From the course: After Effects CC 2021 Essential Training: Motion Graphics

What is compositing? - After Effects Tutorial

From the course: After Effects CC 2021 Essential Training: Motion Graphics

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What is compositing?

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- [Instructor] What is compositing? Loosely, it's the combining of two or more visual elements into a cohesive image. As an example, compositing in its simplest form is placing one image on top of another, like adding a layer of text onto a picture or drawing a goofy mustache on a selfie. Building up smaller components like text, still images, and live action footage to create a more complex composition is often the end goal that could not be achieved otherwise. Here, we'll take a look at an overview of some of the key concepts and terminology associated with compositing and how they fit within the realm of motion graphics. So here are some key concepts. We have mattes, rotoscoping, keying, blending modes, and tracking. Mattes are used to isolate one portion of an image. It essentially cuts out the portion of a picture that you want to use or throw away. In After Effects, mattes can be generated a number of ways, including creating a mask directly on a layer or by having one layer reference the transparency of another. That's a method called track matting. You can use keying effects or the Roto Brush tool. No matter how the matte is derived, use of mattes make it possible to isolate part of an image to layer on top of other pieces. Rotoscoping is the process of essentially tracing over an area of footage you wish to isolate. The end result is the generation of a matte by use of an animated mask. Keying, this is another method to generate a matte by creating transparency over the range of a certain color. Green screen or blue screen keying allows to take any area in our footage that is that color and eliminate it, which results in everything else becoming isolated. Blending modes. After Effects allows one layers pixels to interact with the layers below it using the color and brightness of the pixels and combining it mathematically. These blending modes can often darken or lighten the overall image. Oftentimes in motion graphics, we'll want to have one element move around with another. And while we can use parenting to link up to hand keyframed animation, we need a different approach when using live-action footage. Tracking is the process by which we could have After Effects follow the position, scale, and rotation of a given point in the footage. From here, we can use the tracked information to link up any other element. There are two methods of tracking, point and planar tracking. Point tracking follows a particular pixel around the frame while playing our tracking uses planes in the footage to derive motion. In addition to tracking the motion of something in the footage, we can also track the camera used to create the footage. Camera tracking produces results that move in After Effects camera inside the software the same way the physical camera moved in the real world when acquiring the footage. One of the use of tracking is to invert the results of a track, and that would result in the stabilization of the motion. These are core ideas involved with compositing and we'll explore a few of these further as it relates to motion graphics in movies to come.

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