118 lines
5.2 KiB
Plaintext
118 lines
5.2 KiB
Plaintext
---
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title: After Effects Expressions
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subtitle: Animation on steroïds.
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lang: en
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slug: "after-effects-expressions"
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excerpt: Expressions in After Effects have always been blurry for me. I know they exist, I know they're powerful, I know it could save a lot of time and clean complex keyframe filled compositions but… They are hard to learn!
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tags: ["Design"]
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type: articles
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createdAt: "2019-04-24T09:00:00.000Z"
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code: true
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---
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import AstroImage from "../../../components/AstroImage.astro";
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export const basicExpression =
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"https://assets.nardu.in/basic_expression_d81b12f1ac.jpeg";
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export const shortcut = "https://assets.nardu.in/shortcut_39cc19d383.jpeg";
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## An ever lasting battle
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There is very little documentation and the existing one is hard to find or very old. Very often I just don't have the time to dive into expression learning while animating even though it could help the entire project on the long term.
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So the last time I had to do a complex animation, **I took the damn time!**
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## The begining of the end (of keyframes).
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Everyone uses expressions whether they know it or not. Most of the time it's a rather transparent process for the animator. For example: when parenting a property to another one, After Effects creates an expression for us.
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<AstroImage
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src={basicExpression}
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width="728"
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height="80"
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alt="Parenting the position of the form to a null creates an expression."
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/>
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Over the last updates, Adobe has made an effort to make expressions more accessible to everyone. For example, the expression box is now resembling a code editor thanks to code-coloring and auto-completion features. After Effects expression feel like JavaScript with custom functions.
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Those custom functions can be called through a menu once you enabled the expressions on a property. It offers organized shortcut and proper syntax to all of AE native functions and a bunch of JavaScript standard ones.
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<AstroImage
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src={shortcut}
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width="728"
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height="322"
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alt="Alt + Click the stopwatch to access the shortcuts."
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/>
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## So I need to learn javascript to do motion design now?
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### Why bother?
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I know that most animators don't have any kind of development background. However, if Adobe thought it best to let us use expressions, I think we ought to, at least, try.
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> A lot of incredible professionals like [Mt Mograph](https://www.mtmograph.com/) and [Video Copilot](https://videocopilot.net/) use expressions.
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Like every optimization process, building an expressions knowledge takes time. However, like all optimization process, you will benefit from it afterwards.
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### Where to learn
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I've gathered a list of my favourite learning grounds. Plenty more exist, **go get'em!**
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- [Adobe official expression starter guide (FR)](https://helpx.adobe.com/fr/after-effects/using/expression-language-reference.html)
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- [Adobe official expression basic (EN)](https://helpx.adobe.com/after-effects/using/expression-basics.html)
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- [Adobe forums for expressions](https://community.adobe.com/t5/after-effects/bd-p/after-effects?page=1&sort=latest_replies&filter=all&topics=label-expressions)
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- [Creative Cow expressions forums](https://creativecow.net/forums/forum/adobe-after-effects-expressions/)
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- [Youtube channel about expressions](https://www.youtube.com/playlist?list=PLvr5U5ZSt6IzHyvSL9fo0M9NRPsTvra31)
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- [All expressions explained](http://aescript.jecool.net/reference/)
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- [All expressions explained again](http://expressions.aenhancers.com/index.html)
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- [Nice examples of basic expressions](https://www.schoolofmotion.com/tutorials/amazing-expressions-in-after-effects)
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## Real world example
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### Number counter
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Let's say you need to animate a rather simple counter from 0% to 100%.
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- Start by creating a text layer. Define your typographic choices, colours, etc.
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- On the effect menu add expression options > slider control
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- Alt + Click the Source text property
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<video width="728" loop controls preload="metadata">
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<source src="https://assets.nardu.in/alt-counter.mp4" type="video/mp4" />
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</video>
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- Parent the source text to the slider control through the pickwhip.
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<video width="462" loop controls preload="metadata">
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<source src="https://assets.nardu.in/pickwhip.mp4" type="video/mp4" />
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</video>
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You should get something like this in the expressions panel:
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```javascript
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effect("Slider Control")("Slider")
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```
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- Set two keyframes on the slider from 0 to 100. The text should update accordingly.
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- By default, After Effects does not round numbers. In the expression panel, wrap your expression with the `Math.round()` function.
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<video width="728" loop controls preload="metadata">
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<source src="https://assets.nardu.in/round.mp4" type="video/mp4" />
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</video>
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```javascript
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Math.round(effect("Slider Control")("Slider"))
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```
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Great! We have a working counter. But we wanted a percentage counter. We could add a % glyph in another text layer but let's not.
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Still in the expression panel, we're going to add a string containing the % glyph, using basic JavaScript concatenation: `+ '%'`
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```javascript
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Math.round(effect("Slider Control")("Slider")) + '%'
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```
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<video width="538" loop controls preload="metadata">
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<source src="https://assets.nardu.in/percent.mp4" type="video/mp4" />
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</video>
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**And there we go!** A fully functioning and customizable counter using a slider controller and expressions.
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