Geduld - After Effects Expressions: Includes index

After Effects Expressions After Effects Expressions By Marcus Geduld Focal Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK Copyright 2009 Marcus Geduld. Published by Elsevier Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Permissions may be sought directly from Elseviers Science & Technology Rights Department in Oxford, UK: phone: (+44) 1865 843830, fax: (+44) 1865 853333, E-mail: ), by selecting Support & Contact then Copyright and Permission and then Obtaining Permissions. Library of Congress Cataloging-in-Publication Data Geduld, Marcus. Library of Congress Cataloging-in-Publication Data Geduld, Marcus.

After Effects Expressions/by Marcus Geduld. p. cm. Includes index. ISBN 978-0-240-80936-6 (pbk. paper) 1. paper) 1.

CinematographySpecial effects Data processing. 2. Adobe After Effects. 3. Computer animation. Title. Title.

TR858.G35 2008 778.5345dc22 2008034230 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ISBN: 978-0-240-80936-6 For information on all Focal Press publications visit our website at www.elsevierdirect.com To Lisa This book is an expression of my everlasting love. Acknowledgments I am deeply indebted to Dan Ebberts, the world-renowned Expressions guru. Dan, thanks for the e-mails, the suggestions, and the support. Id also like to thank AE experts Chris Meyers, Trish Meyers, Angie Taylor and the crew at creativecow.net for ideas and inspiration. When I started this book, I was working for Future Media Concepts.

I now work for nabbr.com. I thank both companies for their support and for their stimulating work environments. Special thanks to Paul Temme, Dennis McGonagle, and Lianne Hong at Focal Press and my colleague Rich Harrington at Rhed Pixel. Most of all, thank you, Lisa, for putting up with all my geeky passions. Introduction What are Expressions? Expressions are tools. Just as you use the Rotation tool and the Pen tool, you can use Expressions to control animation and composition in After Effects (AE).

Whereas you use most tools by clicking on their icons (e.g., the pointer or the pen) and clicking or dragging with the mouse, you use Expressions by typing commands on the keyboard. Thats what Expressions are: typed commands. You type these commands to tell AE what to do, andassuming AE understands your commandsit does what you want it to do. But you dont always have to type to add an Expression. There are some clever click-and-drag tools that will save you time. But these tools just do the typing for you.

Expressions are still typed commands. Expressions are also like recipesdirections for baking some yummy dessert: First, mix eggs and flour; then add sugar; then bake at 375 degrees for 20 minutes. Imagine you wrote such a recipe, and a helpful robot (wearing a chefs hat and apron) read it, followed the directions, and baked you a cake. With Expressions, you type out the instructions, and the robotAfter Effectsbakes you a cool effect. Most Expressions command AE to bake numbers. For instance, the Expression 1 + 2 commands AE to bake the number 3.

Its as if youve typed, take a yummy one and a scrumptious two, and pop them in the addition oven. The AE robot does so, and a few nanoseconds later, it hands you a steaming, delicious 3 on a plate. (Dont worry; most of the Expressions youll use, at least when youre starting out, wont look like math problems.) Im An Artist! Why should I Care about Numbers? Because numbers rule After Effects. In AE, numbers drive nearly every aspect of your work. AE tends to hide this fact from you, though not very well, because the numbers are always right there for you to see. The numbers Im talking about are the ones you see in the Timeline, to-the-right-of the Transform properties. The numbers Im talking about are the ones you see in the Timeline, to-the-right-of the Transform properties.

You may think of Rotation as something you control by spinning a layer with the Rotate tool, but AE thinks of it as, say, the number 45, as in 45 degrees clockwise; you may think of Position as dragging a layer down and to the right, but AE thinks of it as, perhaps, 150 and 223, x and y coordinates. In fact, all the user-friendly tools that manipulate layersthe Selection tool, the Rotate tool, and so onare just widgets that let you build and change numbers. When you drag a layer to the left, you may think of yourself as, well, dragging it to the left. But what youre really doing is changing the layers x-coordinate number. AE then uses this number to remember how far left you want the layer to be. It doesnt remember that you dragged the layer; it remembers the number.

And next time you preview the Comp, it uses this number to determine the placement of the layer. Expressions are another way to control such numbers. Expressions are typed commands that control numbers. These numbers dont just control the Transform properties; they also control Effect properties, like the blurriness of a Gaussian Blur (which is a number too). Because nearly everything you do to layers involves manipulating some propertys numbers (an Effect propertys numbers or a Transform propertys numbers) and because Expressions let you control a properties numbers, Expressions are very powerful. What Can I do with Expressions? At their most basic (but still very powerful) level, Expressions can act as super-parenting tools.

If youve ever used the parenting feature in AE, you know that it allows you to make one layer the parent of another. The child layer will move when its parent moves, scale when its parent scales, and rotate when its parent rotates. But thats all. If you fade a parent by adjusting its opacity, the child does not fade; if you blur the parent (saw with the Gaussian Blur effect), the child does not blur. Expressions crash through these fences. They allow you to hook any two properties together.

Thats properties, not layers. So layer As scale property can control layer Bs scale property so that when A gets bigger, B gets bigger. More intriguing, you can create an opposite Expression so that when A gets bigger, B gets smaller. Or, even more intriguing, you can hook As position to Bs scale, so that when A moves to the left, B gets smaller, and when A moves to the right, B gets bigger. You can throw a glow effect onto a Text layer and use an Expression to make the text resize as the glow becomes more intense. Expressions give you a mechanism for allowing any property to control any other property (or properties) in all sorts of complex, useful, and creative ways.

With Expressions, its as if you live in a wacky house where you can connect your toaster to your hair dryer and your washing machine to your garage door. Start the washing machine, and the garage door opens. But thats not all. Expressions provide you with commands, like wiggle and loopOut, which cause layers to behave in complex ways. You dont need to spend hours animating them with keyframes; you just issue a command and the layer does your bidding. (Wiggle lets you randomize a property, so, for instance, the layer might randomly change colors as it moves across the screen; loopOut allows you to selectively loop one aspect of a layer, so you could make the layer bounce up and down repeatedly while, at the same time, it moves once from left to right and fades out.) Expressions let you link several (dozens, even hundreds) of layers together so that they act as a team; with Expressions, you can create complex movements, such as pendulum swings and elliptical orbits, which are really hard to animate with keyframes.