75 lines
4.1 KiB
Markdown
75 lines
4.1 KiB
Markdown
---
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title: "Proximity Structures: Playing around with PixiJS"
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layout: post
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image: /img/blog/proximity-structures.png
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---
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I've been messing around with a library called [PixiJS](http://www.pixijs.com/)
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which allows you to create WebGL animations which will fall back to HTML5 canvas
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if WebGL is not available in the browser. I mostly like it because the API is
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similar to HTML5 canvas which [I was already familiar
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with](https://github.com/thallada/thallada.github.io/blob/master/js/magic.js). I
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can't say that I like the PixiJS API and documentation that much, though. For
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this project, I mostly just used a small portion of it to create [WebGL (GPU
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accelerated) primitive
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shapes](http://www.goodboydigital.com/pixi-webgl-primitives/) (lines and
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circles).
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**Play with it here**: [http://proximity.hallada.net](http://proximity.hallada.net)
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**Read/clone the code here**: [https://github.com/thallada/proximity-structures](https://github.com/thallada/proximity-structures)
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The idea was inspired by
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[all](https://thumb9.shutterstock.com/display_pic_with_logo/3217643/418838422/stock-vector-abstract-technology-futuristic-network-418838422.jpg)
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[those](https://ak5.picdn.net/shutterstock/videos/27007555/thumb/10.jpg)
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[countless](https://ak9.picdn.net/shutterstock/videos/10477484/thumb/1.jpg)
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[node](https://ak3.picdn.net/shutterstock/videos/25825727/thumb/1.jpg)
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[network](https://t4.ftcdn.net/jpg/00/93/24/21/500_F_93242102_mqtDljufY7CNY0wMxunSbyDi23yNs1DU.jpg)
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[graphics](https://ak6.picdn.net/shutterstock/videos/12997085/thumb/1.jpg) that
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I see all the time as stock graphics on generic tech articles.
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This was really fun to program. I didn't care much about perfect code, I just
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kept hacking one thing onto another while watching the instantaneous feedback of
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the points and lines responding to my changes until I had something worth
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sharing.
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### Details
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The majority of the animation you see is based on
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[tweening](https://en.wikipedia.org/wiki/Inbetweening). Each point has an origin
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and destination stored in memory. Every clock tick (orchestrated by the almighty
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[requestAnimationFrame](https://developer.mozilla.org/en-US/docs/Web/API/window/requestAnimationFrame)),
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the main loop calculates where each point should be in the path between its
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origin and destination based on how long until it completes its "cycle". There
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is a global `cycleDuration`, defaulted to 60. Every frame increments the cycle
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counter by 1 until it reaches 60, at which point it folds over back to 0. Every
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point is assigned a number between 1 and 60. This is its start cycle. When the
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global cycle counter equals a point's start cycle number, the point has reached
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its destination and a new target destination is randomly chosen.
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Each point is also randomly assigned a color. When a point is within
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`connectionDistance` of another point in the canvas, a line is drawn between the
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two points, their colors are averaged, and the points' colors become the average
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color weighted by the distance between the points. You can see clusters of
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points converging on a color in the animation.
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Click interaction is implemented by modifying point target destinations within a
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radius around the click. Initially, a mouse hover will push points away.
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Clicking and holding will draw points in, progressively growing the effect
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radius in the process to capture more and more points.
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I thought it was really neat that without integrating any physics engine
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whatsoever, I ended up with something that looked sort of physics based thanks
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to the tweening functions. Changing the tweening functions that the points use
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seems to change the physical properties and interactions of the points. The
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elastic tweening function makes the connections between the points snap like
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rubber bands. And, while I am not drawing any explicit polygons, just points and
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lines based on proximity, it sometimes looks like the points are coalescing into
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some three-dimensional structure.
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I'll probably make another procedural animation like this in the future since it
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was so fun. Next time, I'll probably start from the get-go in ES2015 (or ES7,
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or ES8??) and proper data structures.
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