Gobos and Gels

Finishing our tour of 3D lighting in After Effects, we’ll discuss gobos and gels. For those new to lighting, a gobo is an opaque object that blocks off some of the rays cast by a light, either to more carefully control where they fall, or to give the impression of light streaming through an object such as a window blind or the leaves of a tree. A gel is a translucent object placed in front of a light, which colorizes the rays cast by it. It is generally a solid color, but can be a graphic. Here are a few different approaches to replicating these inside After Effects.

Lurking in the Shadows

The second stop in our overview of 3D lighting in After Effects is the subject of shadows. In the Dark Ages (before version 5, when After Effects got 3D), in order to fake the all-important perspective clue of one layer darkening another layer behind it, we needed to use plug-ins such as the stock Drop Shadow effect, Real Shadows from Red Giant Software’s Image Lounge, and CC Radial Shadow (formerly part of Cycore Cult FX; now included with After Effects). With the introduction of 3D space in After Effects back in version 5, the correct casting of shadows between layers became somewhat “automatic” – as long as you know how to set it up.

Blinded by the Light

The 3D implementation in After Effects is very flexible. You can selectively place some layers in 3D space, and leave others in normal 2D. If you don’t create a camera, the composition reverts to a default camera. If you do create a camera to fly around your 3D layers, you don’t need to create lights – by default, the layers keep their original colors, as if perfectly illuminated. Or, you can add 3D lights to your composition.

Lighting is probably the most subtle and powerful aspect of 3D in After Effects, as it can create wonderfully moody shifts in brightness and color, as well as “automatic” shadows without needing to tweak Drop Shadow effects for each layer. Lighting is also probably the least understood aspect of 3D in After Effects. Therefore, we’re going to spend the next few columns discussing lighting tips and tricks, starting this column with the basics: the differences between – and uses of – diffuse, specular, and ambient lighting effects.

2D Texture Mapping

We find it useful to employ both 2D and 3D programs in our work - not just to create different looks, but also because techniques learned in one can provide inspiration for a new approach in the other. One example of this is in the area of texture mapping - making a computer-generated object or surface appear to have a physical texture, with real paint or decals applied to it.

In 3D, advanced users wouldn’t dream of leaving a surface untextured; they would apply treatments to make it appear more realistic (or surrealistic, if that’s what the scene calls for). Then why do so many 2D artists settle for plain, solid-colored text? Sometimes, this is the best approach to clearly convey a message - but it can be interesting to consider texturing our 2D objects as well.

There are a series of three tricks we employ to add texture to our text - especially if it is supposed to look like it has been applied to another object in our composite. Let’s take the challenge of making some text appear painted onto a the side of a building to see how we would apply these techniques.

Luminance Ranges in Video

It would seem like a simple concept: “black” is the darkest color you can have; “white” is the brightest color. However, not all video hardware and software think this way. Quite often, systems can go “darker” than black and “brighter” than white, allowing safety margins for certain situations.

This means that some systems uses different values for black and white than others. This can cause a lot of problems for a video editor or artist who uses a variety of tools during a production, because images may shift in relative brightness and contrast for no apparent reason. Compounding this problem is a lack of accurate information about how to manage these shifts. But if you ignore them, the results can range from washed-out images to illegal color values.

Therefore, you will need to take it upon yourself to be aware of the black and white definitions that different systems are using, and to translate between them as needed. We will also discuss the oft-confused analog concept of “set up” and how it relates to these digital values. It initially requires a bit of a mind-twist, but will pay off in the long run. We will be using After Effects for some of the examples later in this article, but these concepts apply to all systems - so read on…

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