Figure 13.2 shows how the same object at the same size indicates its depth by its color. The background has great foreground and background reference for black and white levels; although the rear plane looks icy blue against gray, it matches the look of gray objects in the distance of the image.

Figure 13.2. One plane (white circle) is composited as if it is a toy model in the foreground, the other (black circle) as if it is crossing the sky further in the distance; a look at just the planes shows them to be identical but for their color (left). The difference between a toy model airplane flying close, a real airplane flying nearby, and the same plane in the distant sky is conveyed with the use of Scale, but just as importantly, with Levels that show the influence of atmospheric haze.

The technique used here is the same as the one outlined in Chapter 5 with the additional twist that now you understand how atmospheric haze influences the color of the scene. Knowing how this works from studying a scene like this one helps you create something similar from scratch even without such good reference.

The plane as a foreground element seems to make life easier by containing a full range of monochrome colors. When matching a more colorful or monochrome element, you can always create a small solid and add the default Ramp effect. With such a reference element, it is simple to add the proper depth cueing with Levels and then apply the setting to the final element (Figure 13.3).

Figure 13.3. If your foreground layer lacks the full range of values, match a grayscale gradient, then swap in the element. These gradient squares have the same settings as the planes in 13.2.

To re-create depth cues in a shot from scratch, you must somehow separate the shot into planes of distance. If the source imagery is computer-generated, the 3D program that created it can also generate a depth map for you to use. If not, you can slice the image into planes of distance, or you can make your own depth map to weight the distance of the objects in frame (Figure 13.4).

Figure 13.4. This grayscale depth map is made up of individual roto shapes, each shaded for relative distance (further elucidated in Advanced Rotoscoping Techniques for Adobe After Effects by Pete O’Connell, Creative Cow).

There are several ways in which a depth map can be used, but the simplest approach is probably to apply it to an adjustment layer as a Luma (or Luma Inverted) Matte, and then add Levels or other color correction adjustment to the adjustment layer. Depth cueing would be applied to the furthest elements, so applying this matte as a Luma Inverted Matte and then flashing the blacks (raising the Output Black level in Levels) adds the effect of atmosphere on the scene.

Tip

Getting reference is easy for anyone with an Internet connection these days, thanks to sites and services like flickr.com and Google image search.

Depth data may also be rendered and stored in an RPF file, as in Figure 13.5 (which is taken from an example included on the disc as part of 13_multipass.aep). RPF files are in some ways crude, lacking even thresholding in the edges (let alone higher bit depths), but they can contain several types of 3D data, as are listed in the 3D Channel menu. This data can be used directly by a few effects to simulate 3D, including Particle Playground, which accepts RPF data as an influence map.

Figure 13.5. An RPF image close-up can be clearly seen to have jagged edge pixels, but a depth map does not have to be perfectly pristine. An EXR does not have this limitation. (Created by Fred Lewis; used with permission from Inhance Digital, Boeing, and the Navy UCAV program.)

Notes

One good reason to use a basic 3D render of a scene as the basis for a matte painting is that the perspective and lens angle can be used not only for reference, but to generate a depth map, even if the entire scene is painted over.

More extreme conditions may demand actual 3D particles, which are saved for later in the chapter.

Study the actual sky (there may be one nearby as you read this) or even better, study reference images, and you may notice that the blue color desaturates near the horizon, cloudless skies are not always so easy to come by, and even clear blue skies are not as saturated as they might sometimes seem.

Some combination of a color keyer, such as Keylight, and a hi-con luminance matte pass or a garbage matte, as needed, can remove the existing sky in your shot, leaving nice edges around the foreground. Chapter 6 focuses on strategies for employing these, and Chapter 7 describes supporting strategies when keys and garbage mattes fail.

The first step of sky replacement is to remove the existing “sky” (which may include other items at infinite distance, such as buildings and clouds) by developing a matte for it. As you do this, place the replacement sky in the background; a sky matte typically does not have to be as exacting as a blue-screen key if the replacement sky is also fundamentally blue, or if the whole image is radically color corrected as in Figure 13.7.

Figure 13.7. A very challenging matte for several reasons, not the least of which is the uneven desaturated quality of the sky. Placing the pigeon in a radically different environment requires color and grain matching to compensate for a less than stellar source.

A locked-off shot can be completed with the creation of the matte and a color match to the new sky. If, however, there is camera movement in the shot, you might assume that a 3D track is needed to properly add a new sky element.

Typically, that’s overkill. Instead, consider

The basic phenomenon to re-create is the scenery at infinite distance that moves less than objects in the foreground. This is the parallax effect, which is less pronounced with a long, telephoto lens, and much more obvious with a wide angle. For the match in Figure 13.6, a still shot (no perspective) was skewed to match the correct angle and tracked in 2D; the lens angle was long enough and the shot brief enough that they got away with it. A simpler example is included on the disc.

When covering the entire foreground evenly with smoke or mist, a more realistic look is achieved using two or three separate overlapping layers with offset positions (Figure 13.9). The unexpected byproduct of layering 2D particle layers in this manner is that they take on the illusion of depth and volume.

Figure 13.9. Overlay layers of fabricated smoke to add dimensionality and depth.

The eye perceives changes in parallax between the foreground and background and automatically assumes these to be a byproduct of full three-dimensionality, yet you save the time and trouble of a 3D volumetric particle render. Of course, you’re limited to instances in which particles don’t interact substantially with movement from objects in the scene; otherwise, you instantly graduate to some very tricky 3D effects (although I have seen it done in After Effects with warps).

Notes

Fractal Noise texture maps maintain the advantage over Turbulent Noise in that they can loop seamlessly (allowing reuse on shots of varying length). In Evolution Options, enable Cycle Evolution, and animate Evolution in whole revolutions (say, from 0° 2 × 0.0°). Set the Cycle (in Revolutions) parameter to the number of total revolutions (2). The first and last keyframes now match, and a loopOut("cycle") expression continues this loop infinitely.

Particle layers can be combined with the background via blending modes, or they can be applied as a Luma Matte to a colored solid (allowing you to specify the color of the particles without having a blending mode change it).

To add smoke to a generalized area of the frame, a big elliptical mask with a high feather setting (in the triple digits even for video resolution) will do the trick; if the borders of the smoke area are apparent, increase the mask feather even further (Figure 13.10).

Figure 13.10. This mask of a single smoke element from the shot in Figure 13.8 has a feather value in the hundreds. The softness of the mask helps to sell the element as smoke and works well overlaid with other, similarly feathered masked elements.

The same effect you get when you layer several instances of Turbulent or Fractal Noise can aid the illusion of moving forward through a misty cloud. That’s done simply enough (for an example of flying through a synthetic cloud, see 13_smokyLayers.aep), but how often does your shot consist of just moving through a misty cloud? Most of the time, clouds of smoke or mist are added to an existing shot.

You can use the technique for emulating 3D tracking (see Chapter 8) to make the smoke hold its place in a particular area of the scene as the camera moves through (or above) it. To make this work, keep a few points in mind:

Close-Up: Selling the Effect with Diffraction

There is more to adding a cloud to a realistic shot than a simple A over B comp; water elements in the air, whether in spray, mist, or clouds, not only occlude light but diffract it. This diffraction effect can be simulated by applying Compound Blur to an adjustment layer between the fog and the background and using a precomposed (or prerendered) version of the fog element as its Blur layer.

This usage of Compound Blur is is detailed further in the next chapter, where it is used to enhance the effect of smoky haze.

13_smokyFlyover.aep features just such an effect of moving forward through clouds. It combines the tracking of each shot carefully into place with the phenomenon of parallax, whereby overlapping layers swirl across one another in a believable manner. Mist and smoke seem to be a volume but they actually often behave more like overlapping, translucent planes—individual clouds of mist and smoke.

Mesh Warp lays a grid of Bézier handles over the frame; to animate distortion, set a keyframe for the Distortion Mesh property at frame 0, then move the points of the grid and realign the Bézier handles associated with each point to bend to the vertices between points. The image to which this effect is applied follows the shape of the grid.

By default, Mesh Warp begins with a seven-by-seven grid. Before you do anything else, make sure that the size of the grid makes sense for your image; you might want to increase its size for a high-resolution project, and you can reduce the number of rows to fit the aspect ratio of your shot, for a grid of squares (Figure 13.13).

Figure 13.13. The Mesh Warp controls are simple, just a grid of points and vectors. You can preset the number and quality; more is not necessarily better (just more to control). Points can be multiselected and dragged, and each point contains Bézier handles for warping the adjacent vectors.

Tip

Mesh Warp, like many distortion tools, renders rather slowly. As you rough in the motion, feel free to work at quarter-resolution. When you’ve finalized your animation, you can save a lot of time by pre-rendering it (see Chapter 4).

You can’t typically get away with dragging a point more than about halfway toward any other point; watch carefully for artifacts of stretching and tearing as you work, and preview often. If you see stretching, realign adjacent points and handles to compensate. There is no better way to learn about this than to experiment.

I have found that the best results with Mesh Warp use minimal animation of the mesh, animating instead the element that moves underneath it.

Mesh Warp is appropriate for gross distortions of an entire element. The Liquify effect is a brush-based system for fine distortions. 13_smokeCloud.aep includes a composition that employs Liquify to swirl a cloud. Following is a brief orientation to this toolset, but as with most brush-based painterly tools, there is no substitute for trying it hands-on.

The principle behind Liquify is actually similar to that of Mesh Warp; enable View Mesh under View Options and you’ll see that you’re still just manipulating a grid, albeit a finer one that would be cumbersome to adjust point by point—hence the brush interface.

Of the brushes included with Liquify, the first two along the top row, Warp and Turbulence, are most often used (Figure 13.14). Warp has a similar effect to moving a point in Mesh Warp; it simply pushes pixels in the direction you drag the brush. Turbulence scrambles pixels in the path of the brush.

Figure 13.14. Liquify is also a mesh distortion tool, only the mesh is much finer than Mesh Warp’s and it is controlled via brushes, allowing more specific distortions.

The Reconstruction brush (rightmost on the bottom row) is like a selective undo, reversing distortions at the default setting; other options for this brush are contained in the Reconstruction Mode menu (which appears only when the brush is selected).

Liquify has the advantage of allowing hold-out areas. Draw a mask around the area you want to leave untouched by Liquify brushes, but set the Mask mode to None, disabling it. Under Warp Tool Options, select the mask name in the Freeze Area Masked menu.

Liquify was a key addition to the “super cell” element (that huge swirling mass of weather) for the freezing of the New York City sequence in The Day After Tomorrow. Artists at The Orphanage were able to animate matte paintings of the cloud bank, broken down into over a dozen component parts to give the effect the appropriate organic complexity and dimension.

Many effects, including smoke trails, don’t require particle generation in order to be re-created faithfully. This section is included less because the need comes up often and more to show how, with a little creativity, you can combine techniques in After Effects to create effects that you might think require extra tools.

Initial setup of such an effect is simply a matter of starting with a clean plate, painting the smoke trails in a separate still layer, and revealing them over time (presumably behind the aircraft that is creating them). The quickest and easiest way to reveal such an element over time is often by animating a mask, as in Figure 13.15, or you could use techniques described in Chapter 8 to apply a motion tracker to a brush.

Figure 13.15. No procedural effect is needed; animating out masks is quick, simple, and gives full control over the result.

The second stage of this effect is dissipation of the trail; depending on how much wind is present, the trail might drift, spread, and thin out over time. That might mean that in a wide shot, the back of the trail would be more dissipated than the front, or it might mean the whole smoke trail was blown around.

One method is to displace with a black-to-white gradient (created with Ramp) and Compound Blur. The gradient is white at the dissipated end of the trail and black at the source (Figure 13.16a); each point can be animated or tracked in. Compound Blur uses this gradient as its Blur Layer, creating more blur as the ramp becomes more white. Another method, shown in Figure 13.16b, uses a different displacement effect, Turbulent displace, to create the same type of organic noise as in the preceding cloud layers.

Figure 13.16a and b. To dissipate a smoke trail the way the wind would, you can do so using a gradient and Compound Blur, so that the smoke dissipates more over time, or using the Turbulent Displace effect that, like Turbulent Noise, adds fractal noise, using it to displace the straight trails from Figure 13.15.

To make it easier on yourself, look for elements that can be readily isolated and articulated; you should be able to mask the element out with a simple roto or a hi-con matte if it’s not separated to begin with. Look for the point where the object would bend or pivot, place your anchor point there, then animate a gentle rotation. 13_ambientAnim.aep (on the disc) offers a simple animation of the arm of a street-light, held out from the background. A little warp on the clouds behind it, and this still image could convincingly be a brief moving shot (Figure 13.17).

Figure 13.17. It’s impossible to do a full wind dynamics simulation in After Effects, but if there should be a little ambient motion to go with some moving clouds, look for simple ways to add it, such as this wiggle expression tied to the top of the light pole.

Close-Up: Primary and Secondary

Primary animation is the gross movement of the object, the movement of the object as a whole. Secondary animation is the movement of individual parts of the object as a result of inertia. So, for example, a helicopter crashes to the ground: That’s the primary animation. Its rotors and tail bend and shudder at impact: That’s the secondary animation. For the most part, in 2D compositing, your work is isolated to primary animation.

You also have the option of acquiring and adding elements that indicate or add to the effect of wind motion. Figure 13.18 is an element of blowing autumn leaves shot against a black background for easy removal and matting; granted, you could add an element this turbulent only to a scene that either already had signs of gusts in it or that contained only elements that would show no secondary motion from wind whatsoever.

Figure 13.18. Sometimes you can find elements that will enliven your scene when comped in, such as this clip of blowing leaves shot over black. (Footage courtesy of Artbeats.)

Study reference photographs of stormy conditions and you’ll notice some things that they all have in common, as well as others that depend on variables. Here are the steps taken to make a sunny day gloomy (Figure 13.19):

Figure 13.19. An ordinary exterior where “it never rains” becomes a deluge.

Figure 13.20a through e. The progression to a heavy, wet day (top to bottom).

That’s dark, but it looks as dry as a lunar surface. How do you make the background look soaked? It seems like an impossible problem, again, until you study reference. Then it becomes apparent that all of that moisture in the air causes distant highlights to bloom. This is a win-win adjustment (did I really just type that?) because it also makes the scene lovelier to behold.

You can simply add a Glow effect, but it doesn’t offer as much control as the approach I recommend.

Follow these steps:

Figure 13.20e shows the result; it now looks like a wet, cold day, but where’s the rain?

Particular contains all the controls needed to generate custom precipitation; it contains a lot of controls, period. A primer is helpful, to get past the default animation of little white squares emanating out in all directions (click under Preview in Effect Controls to see it). To get started making rain, create a comp-sized 2D solid layer, apply Particular, and

You might think it more correct to boost gravity than velocity, but gravity increases velocity over time (as Galileo discovered) and rain begins falling thousands of feet above; however, this is not something you need to replicate, as no one will know the difference.

You do, however, need to do the following:

From here, you can add Wind and Air Resistance under Physics. If you’re creating snow instead of rain, you might want to customize the Particle Type, even referring to your own Custom layer if necessary for snowflakes.

What is the color of falling rain? The correct answer to this zen koan-like question is that raindrops and snowflakes are translucent. Their appearance is heavily influenced by the background environment, because they behave like tiny falling lenses. They diffract light, defocusing and lowering the contrast of whatever is behind them, but they themselves also pick up the ambient light.

Therefore, on The Day After Tomorrow our crew found success with using the rain or snow element as a track matte for an adjustment layer containing a Fast Blur and a Levels (or Exposure) effect, like a reflective, defocused lens. This type of precipitation changes brightness according to its backlighting, as it should. You may see fit to hold out specific areas and brighten them more, if you see an area where a volumetric light effect might occur.

The final result in Figure 13.19b benefits from a couple of extra touches. The rain is divided into multiple layers, near and far, and motion tracked to match the motion of the car from which we’re watching this scene. Particular has the ability to generate parallax without using multiple layers, but I sometimes find this approach gives me more control over the perspective.

Because we’re looking out a car window, if we want to call attention to the point of view because the next shot reverses to an actor looking out this window, it’s only appropriate that the rain bead up. This is also done with Particular, with Velocity turned off and Custom particles for the droplets.

And because your audience always can tell when you have the details wrong, even if they don’t know exactly what’s wrong, check out Figure 13.22 for how the droplet is designed.

Figure 13.22. It looks jaggy because you don’t want particles to be any higher resolution than they need to be, or they take up massive amounts of render time. There are two keys to creating this particle: It uses the adjusted background, inverted, with the CC Lens effect to create the look. Look at raindrops on a window sometime and notice that, as little lenses, they invert their fisheye view of the scene behind them.

Once again, it is attention to detail and creative license that allow you to simulate the complexities of nature. It can be fun and satisfying to transform a scene using the techniques from this chapter, and it can be even more fun and satisfying to design your own based on the same principles: Study how it really works, and notice details others would miss. Your audience will appreciate the difference every time.

The next chapter heats things up with fire, explosions, and other combustibles.