Adobe After Effects CS5 Visual Effects and Compositing STUDIO TECHNIQUES phần 9 doc

ptg 428 Chapter 13 Climate and the Environment Smoke Trails, Plumes, and More Many effects, including smoke trails, don’t require particle generation in order to be re-created faithfully. This exam- ple shows 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 13.17. Or, you could use techniques described in Chapter 8 to apply a motion tracker to a brush. 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 dis- sipated than the front, or it might mean the whole smoke trail was blown around. Figure 13.16 VFX elements can be shot sideways to maximize image fidelity, and the fact that I was missing a tripod the day I took this doesn’t invalidate it as an element, thanks to motion stabilization. Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 429 III: Creative Explorations 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 13.18); 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, also shown in Figure 13.18, uses a different displacement effect, Turbulent displace, to create the same type of organic noise as in the preceding cloud layers. Figure 13.17 No procedural effect is needed; animating out masks is quick, simple, and gives full control over the result. Figures 13.18 To dissipate a smoke trail the way the wind would, you can use a gradient and Compound Blur, so that the smoke dissipates more over time, or use the Turbulent Displace effect (right) that, like Turbulent Noise, adds fractal noise to displace the straight trails from Figure 13.17. Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 430 Chapter 13 Climate and the Environment Precipitation You might want to create a “dry for wet” effect, taking foot- age that was shot under clear, dry conditions and adding the effects of inclement weather. Not only is it impractical to time a shoot so that you’re fi lming in a storm (in most parts of the world, anyway), but wet, stormy conditions limit shooting possibilities and cut down on available light. Re-creating a storm by having actual water fall in a scene is expensive, complicated, and not necessarily convincing. I like Trapcode Particular (see the demo on the book’s disc) for particles of accumulating rain or snow. This effect outdoes After Effects’ own Particle Playground for features, fl exibility, and fast renders. As the following example shows, Particular is good for more than just falling particles, as well. The Wet Look 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): 1. Replace the sky: placid for stormy (Figure 13.20, part A). 2. Adjust Hue/Saturation—LA for Dublin—to bring out the green mossiness of those dry hills, I’ve knocked out the blues and pulled the reds down and around toward green (Figure 13.20, B). Figure 13.19 An ordinary exterior where “it never rains” (left) becomes a deluge. Want to see this project already set up? Look at 13_dry_for_wet on the book’s disc. Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 431 III: Creative Explorations 3. Exchange Tint—balmy for frigid—a bluish cast is com- mon to rainy scenes (Figure 13.20, C). 4. Fine-tune Curves—low light for daylight—aggressively dropping the gamma while holding the highlights makes things even moodier (Figure 13.20, D). 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, 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: 1. Bring in the background layer again (you can dupli- cate it and delete the applied effects—Ctrl+Shift+E/ Cmd+Shift+E). 2. Add an Adjustment Layer below it and set the dupli- cated background as Luma Matte. 3. Use Levels to make the matte layer a hi-con matte that isolates the highlights to be bloomed. 4. Fast Blur the result to soften the bloom area. 5. On the Adjustment Layer, add Exposure and Fast Blur to bloom the background within the matte selection. Create Precipitation Trapcode 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 anima- tion 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 and apply Particular. Next: 1. Twirl down Emitter and set an Emitter Type. For rain I like Box so that I can easily set its width and depth, but anything besides the default Point and Grid will work. A B C D E Figure 13.20 The progression to a heavy, wet day (top to bottom). Image E shows the result—it now looks like a wet, cold day, but where’s the rain? Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 432 Chapter 13 Climate and the Environment 2. Set Emitter Size to at least the comp width in X, to fi ll the frame. 3. Set Direction to Directional. 4. Set X Rotation to –90 so that the particles fall downward. 5. Boost velocity to go from gently falling snow speed to pelting rain. You might think it more correct to boost gravity than veloc- ity, but gravity increases velocity over time (as Galileo dis- covered) and rain begins falling thousands of feet above. Don’t think too hard, in any case; what you’re after here is realistic-looking weather, not a physics prize. You do, however, need to do the following: 1. Move the Emitter Y Position to 0 or less so that it sits above frame. 2. Increase the Emitter Size Y to get more depth among those falling particles. 3. Crank up the Particles/sec and Physics Time (under Physics) to get enough particles, full blast from the fi rst frame. 4. If the particles are coming up short at the bottom of frame, increase the Life setting under Particle. 5. Enable Motion Blur for the layer and comp to get some nice streaky rain (Figure 13.21). From here, you can add Wind and Air Resistance under Physics. If you’re creating snow instead of rain, you might want to customize Particle Type, even referring to your own Custom layer if necessary for snowfl akes. Composite Precipitation What is the color of falling rain? The correct answer to this Zen Koan–like question is that raindrops and snowfl akes are translucent. Their appearance is heavily infl uenced by the background environment, because they behave like tiny falling lenses. They diffract light, defocusing and Figure 13.21 In the “good enough” category, two passes of rain, one very near, one far, act together to create a watery deluge. Particular could gener- ate this level of depth with a single field, and the midground rain is missing, but planes are much faster to set up for a fast-moving shot like this. The rain falls mainly on two planes. The 13_snowfall folder on the disc contains a setup very much like this one. Customize it or use it to start on the path to creating your own. Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 433 III: Creative Explorations 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 suc- cess 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 refl ective, defocused lens. This type of precipitation changes brightness according to its backlighting, as it should. You may see fi t to hold out specifi c areas and brighten them more, if you spot an area where a volumetric light effect might occur. The fi nal result in Figure 13.19 benefi ts 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 fi nd this approach gives me more control over the perspective. Although you rarely want one without the other, it’s one more example of choosing artistry over scientifi c accuracy. 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 can always 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. 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 prin- ciples: 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 fi re, explosions, and other combustibles. 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 some- time and notice that, as little lenses, they invert their fish-eye view of the scene behind them. Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg This page intentionally left blank Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg CHAPTER 14 Pyrotechnics: Heat, Fire, Explosions Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 436 My nature is to be on set, blowing things up. —Ken Ralston (winner of fi ve Academy Awards for visual effects) Pyrotechnics: Heat, Fire, Explosions I t may not be the true majority, but plenty of people— guys mostly—fi rst become interested in a visual effects career as borderline pyromaniacs or even gun nuts. You have to follow your passion in life, I suppose. Creating a confl agration on the computer isn’t quite as much fun as simply blowing shit up, but maybe it keeps these people off of our streets. The truth is that many types of explosions are still best done through a combination of practical and virtual simu- lations. There are, however, many cases in which composit- ing can save a lot of time, expense, and hazard. Blowing up models and props is fun, but it involves extensive setup and a not insubstantial amount of danger to the cast and crew. Second chances don’t come cheap. On the other hand, there’s often no substitute for the physics of live-action mayhem. I hope it doesn’t come as a disappointment to learn that not everything pyrotechnical can be accomplished start to fi nish in After Effects. Some effects require actual footage of physical or fabricated elements being shot at or blown up, and good reference of such events is immensely benefi cial. Practical elements might rely on After Effects to work, but pyrotechnical shots are equally reliant, if not more so, on practical elements. Firearms Blanks are dangerous, and real guns deadly. To safely cre- ate a shot with realistic gunfi re requires . a realistic-looking gun prop in the scene . some method to mime or generate fi ring action on set Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ptg 437 III: Creative Explorations . the addition of a muzzle fl ash, smoke, cartridge, or shell discharge (where appropriate) . the matching shot showing the result of gunfi re: debris, bullet hits, even blood After Effects can help with all of these to some extent, and handles some of them completely, relieving you of the need for more expensive or dangerous alternatives. The Shoot For the purposes of this discussion let’s assume that you begin with a plate shot of an actor re-creating the action of fi ring a gun, and that the gun that was used on set produces nothing: no muzzle fl ash, no smoke, no shell. All that’s required is some miming by the actor of the recoil, or kick, which is relatively minor with small handguns, and a much bigger deal with a shotgun or fully automatic weapon. Happily, there’s no shortage of reference, as nowhere outside of the NRA is the Second Amendment more cher- ished than in Hollywood movies and television. Granted, most such scenes are themselves staged or manipulated, not documentary realism, but remember, we’re going for cinematic reality here, so if it looks good to you (and the director), by all means use it as reference. Figure 14.1 shows something like the minimal composite to create a realistic shot of a gun being fi red (albeit artfully executed in this case). Depending on the gun, smoke or a spent cartridge might also discharge. As important as the look of the frame is the timing; check your favorite refer- ence carefully and you’ll fi nd that not much, and certainly not the fl ash, lingers longer than a single frame. Stu Maschwitz’s book, The DV Rebel’s Guide (Peachpit Press), is definitive on the subject of creating an action movie, perhaps on a low budget, with the help of After Effects. Included with the cover price, you get a couple of nifty After Effects tools for muzzle flashes and spent shells, and some serious expertise on the subject of making explosive action exciting and real. Figure 14.1 Much of the good reference for movie gunfire is other movies; you typically want the most dramatic and cin- ematic look, which is a single frame of muzzle flash and contact lighting on surrounding elements (right). (Image courtesy of Mars Productions.) Download from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com [...]... spills and, 203–204 edge selection, 202–203 Extract effect for luma keying, 177–1 79 fine tuning and problem solving, 197 – 199 greenscreen and bluescreen and, 182–183 holdout mattes, 199 Linear Color Key, 1 79 181 linear keyers and hi-con mattes, 177 overview of, 174 procedural mattes, 174–177, 199 –201 rotoscoping and paint and, 210 shooting perfect mattes, 205–208 steps in applying keys, 183– 191 color... control, 187, 192 – 194 converting color to black and white, 393 – 394 flashing blacks, 417 Input Black see Input Black Output Black see Output Black Black & White effect, 394 bleach-bypass method, color looks and, 392 blending colors, 1.0 Gamma, 368–3 69, 410 blending modes Add and Screen modes, 99 –100 adjustment layers and, 104, 1 19 Collapse Transformation settings, 116 combining selection techniques, 81... 295 – 297 camera projection (mapping), 290 – 293 camera report on shoots, 274–276 chromatic aberrations, 307–308 color correction, 310–312 convergence and 3D previews, 284–286 depth of focus, 293 – 294 dynamic range, 355 emulating real-world camera, 273 fading while moving away from, 338 fading while turning away from, 341–343 formats and panoramas, 3 09 310 frame rate and realism, 308–3 09 grain, 298 – 299 ... see also Ramp effect backgrounds and, 32 black-to-white, 4 29 inverting highlights and shadows with countergradient, 390 linear gradients, 151 Ramp gradients, 391 grain managing, 299 –303 overview of, 298 – 299 removing, 302–303 when to manage, 303 Graph Editor basic animation and graph view, 48– 49 bouncing ball animation example, 54 ease curves for fixing animations, 49 50 Hold keyframes, 53–54 layers... 390 muzzle flash effect, 4 39 three-way color correctors and, 395 – 396 histogram, Levels adjusting blacks, 138 adjusting whites, 1 39 color channels and, 145–146 problem solving using, 147–148 histograms, Extract, 178–1 79 hits, bullet, 440–441 Hold keyframes (Ctrl+Alt+H/ Cmd+Shift+H) preset transitions, 54 Timeline panel and, 53 holdout masks, tracking, 260 holdout mattes creating, 199 overview of, 191 ... from WoweBook.com Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com image quality and, 198 sky replacement and, 418–4 19 bluescreening see color keying blur motion blur effect, 62–66 three methods for creating blur effects, 401 boke cameras and, 273 creating boke blur effect, 295 – 297 for fuzzy focus, 293 Bordenave, Charles ReverseMaskPath script, 97 TrackerViz script, 246 bouncing... ), JavaScript, 325 deforming footage, 226–2 29 delta (difference), mattes and, 193 density, mask, 93 depth cues, 416 infinite depth in sky replacement, 420 maps, 416–418 particulate matter influencing depth perception, 414–415 depth of focus (field) benefits of multipass rendering, 407 boke blur, 295 – 297 overview of, 273, 293 – 294 rack focus and image planes, 294 – 295 Despill setting, in matte creation, 186... animations, 49 50 keyframes and, 2 89 Easy Ease, 49 50 Ebberts, Dan, 114 Edge Color Correction in Keylight, 190 spill suppression, 197 edges double-matte method (core and edge) and, 193 edge multiplication, 85–88 isolating when color keying, 175 optics of, 82–84 Roto Brush and, 215 selection for color keying, 202–203 Edit Original (Ctrl+E/Cmd+E), 14, 282 editing expressions, 317 keyframe values, 52–53 effects. .. Fill, Shape layers, 91 film Cineon log space and, 355 digital, 355–357 formats, 276 storing, 351 Film Size, Camera Settings, 272 filters, virtual lens, 392 – 393 fire effects, 448–453 adding dimensionality to, 451–453 composites for, 4 49 450 creating fire elements, 448–4 49 light interactions and, 450–451 overview of, 448 firearms, 436–441 hits and squibs, 440–441 muzzle flash and smoke, 438–4 39 overview of, 436–437... multipass compositing, 406–411 previewing in AE, 284–286 projecting still images into, 291 – 292 render order of 3D layers, 121 track mattes and, 105 4:3 film format, 3 09 8-bit-per-channel color fidelity, 371–372 color values, 3 49 350 RGB representation, 353 16 :9 film format, 3 09 16-bit-per-channel, 3 49 350 32-bit-per-channel color values, 366–367 output and, 370–371 A absolute time, frame rate and, 66–67 . low budget, with the help of After Effects. Included with the cover price, you get a couple of nifty After Effects tools for muzzle flashes and spent shells, and some serious expertise on. gunplay will typically demand a mixture of on-set action and postproduction enhancement. Figure 14.4 shows a before -and -after addition of a bullet hit purely in After Effects. Here the bullet. similar qualities (Figure 14.11) and the same techniques will sell the effect. There are a couple of built-in effects that will create light- ning in After Effects. With either Lightning or