It’s our great pleasure to support active members of the Web design  and development community. Today, we’re proud to present the Jelly Navigation Menu  that shows the power of PaperJS and TweenJS when used together. This  article is yet another golden nugget of our series of various tools,  libraries and techniques.
There is no doubt that the Web helps designers and developers find the best inspiration and resources for their projects. Even though there are a bunch of different tutorials and tips available online, I feel that HTML5 canvas techniques are missing the most. Good news: I had the chance to fulfill this wide gap. In this article, I would like to share my experience and story of how I brought the “Jelly Navigation Menu” to life. Credits go to Capptivate.co and Ashleigh Brennan’s icons — they were my inspiration for this project.
I used PaperJS for the canvas graphics and TweenJS for the animations. Both of them tend to freak out some folks, but don’t worry, they are really intuitive and easy to understand. If you’d like to learn how to set up PaperJS and TweenJS environments, you can fork this cool bootstrap pen for online fun or this git repo if you want to experiment locally.

A preview of the Jelly Navigation Menu.

In Paper.js, paths are represented by a sequence of segments that are connected by curves. A segment consists of a point and two handles, defining the location and direction of the curves. See the handles in action.
All we need to do is to change the
That’s it! We’re almost done! It couldn’t be any easier, right? Try out the scrolling here.

The reason why we need to use
There is no doubt that the Web helps designers and developers find the best inspiration and resources for their projects. Even though there are a bunch of different tutorials and tips available online, I feel that HTML5 canvas techniques are missing the most. Good news: I had the chance to fulfill this wide gap. In this article, I would like to share my experience and story of how I brought the “Jelly Navigation Menu” to life. Credits go to Capptivate.co and Ashleigh Brennan’s icons — they were my inspiration for this project.
Before We Start
The source code for this project was originally written in CoffeeScript — I believe it’s a better way to express and share JavaScript code that way. I will refer to CoffeScript’s source in code sections within this post and you’ll also notice links to CodePens that have been rewritten in JavaScript and represent local parts of code as well. I recommend downloading the source code on GitHub so you can easily follow me while I explain the necessary code in detail.I used PaperJS for the canvas graphics and TweenJS for the animations. Both of them tend to freak out some folks, but don’t worry, they are really intuitive and easy to understand. If you’d like to learn how to set up PaperJS and TweenJS environments, you can fork this cool bootstrap pen for online fun or this git repo if you want to experiment locally.

A preview of the Jelly Navigation Menu.
First Step: Changing The Section Shape
Our first aim is to change the menu section shape by manipulating the curves. Every object is made up of anchor points. These points are connected with each other by curves. So each point has “In” and “Out” handles to define the location and direction of specific curves. Folks who work with vector editors should feel comfortable with this step.
In Paper.js, paths are represented by a sequence of segments that are connected by curves. A segment consists of a point and two handles, defining the location and direction of the curves. See the handles in action.
All we need to do is to change the
handleOut position of the top-left and bottom-right points. To achieve this, I wrote simple so-called “toppie” and “bottie” functions:toppie:(amount)->
  @base.segments[1].handleOut.y = amount
  @base.segments[1].handleOut.x = (@wh/2)
bottie:(amount)->
  @base.segments[3].handleOut.y = amount
  @base.segments[3].handleOut.x = - @wh/2
# @wh/2 is section center.
# @base variable holds section's rectangle path.Second Step: Calculating The Scrolling Speed
So the next thing that needs to be done is to calculate the scrolling speed and direction, and then pass this data to thebottie and toppie  functions. We can listen to the container’s scrolling event and  determine the current scrolling position (in my case the “container” is a  #wrapper element whereas it is a window object in the pen examples).# get current scroll value
window.PaperSections.next = window.PaperSections.$container.scrollTop()
# and calculate the difference with previous scroll position
window.PaperSections.scrollSpeed = (window.PaperSections.next - window.PaperSections.prev)
# to make it all work, all we have left to do is to save current scroll position to prev variable
window.PaperSections.prev = window.PaperSections.nextwindow.PaperSections is just a global variable. I also made a few minor additions in my implementation:- A silly coefficient to increase scroll speed by multiplying it by 1.2(just played around with it),
- I sliced the scroll speed result by its maximum so that it is not larger than sectionHeight/2,
- I also added a direction coefficient (it could be 1or-1, you can change it indat.guion the top right of the page). This way you can control the reaction direction of sections.
if window.PaperSections.i % 4 is 0
  direction = if window.PaperSections.invertScroll then -1 else 1
  window.PaperSections.next = window.PaperSections.$container.scrollTop()
  window.PaperSections.scrollSpeed = direction*window.PaperSections.slice 1.2*(window.PaperSections.next - window.PaperSections.prev), window.PaperSections.data.sectionheight/2
  window.PaperSections.prev = window.PaperSections.next
  window.PaperSections.i++if window.PaperSections.i % 4 is 0 helps us react on every fourth scroll event — similar to a filter. That function lives in window.PaperSections.scrollControl.That’s it! We’re almost done! It couldn’t be any easier, right? Try out the scrolling here.
Step Three: Make It Jelly!
In this final step, we need to animate thetoppie and bottie functions to 0 with TweenJS’ elastic easing everytime the scrolling stops.3.1 Determine When Scrolling Stops
To do this, let’s add thesetTimeout function to our window.PaperSections.scrollControl function (or scroll)  with 50ms delay. Each time when the scrolling event fires up, the  Timeout is cleared except for the last one, i.e. once scrolling stops,  the code in our timeout will execute.clearTimeout window.PaperSections.timeOut
window.PaperSections.timeOut = setTimeout ->
  window.PaperSections.$container.trigger 'stopScroll'
  window.PaperSections.i = 0
  window.PaperSections.prev = window.PaperSections.$container.scrollTop()
    , 50window.PaperSections.$container.trigger stopScroll  event. We can subscribe to it and launch the animation appropriately.  The other two lines of code are simply being used to reset helper  variables for later scrollSpeed calculations.3.2 Animate Point’s handleOut To “0”
Next, we’ll write thetranslatePointY function to bring  our jelly animation to life. This function will take the object as a  parameter with the following key-value sets:{
  // point to move (our handleOut point)
  point: @base.segments[1].handleOut,
  // destination point
  to: 0,
  // duration of animation
  duration: duration
}translatePointY:(o)->
  # create new tween(from point position) to (options.to position, with duration)
  mTW = new TWEEN.Tween(new Point(o.point)).to(new Point(o.to), o.duration)
  # set easing to Elastic Out
  mTW.easing TWEEN.Easing.Elastic.Out
        
  # on each update set point's Y to current animation point
  mTW.onUpdate ->
    o.point.y = @y
  # finally start the tween
  mTW.start()TWEEN.update() function also has to be added to every frame of the PaperJS animation loop:onFrame = ->
  TWEEN.update()TWEEN.removeAll()stopScroll event and launch the animations by calling our translatePointY function:window.PaperSections.$container.on 'stopScroll', =>
  # calculate animation duration
  duration = window.PaperSections.slice(Math.abs(window.PaperSections.scrollSpeed*25), 1400) or 3000
  # launch animation for top left point
  @translatePointY(
    point:      @base.segments[1].handleOut
    to:           0
    duration: duration
  ).then =>
    # clear scroll speed variable after animation has finished
    # without it section will jump a little when new scroll event fires
    window.PaperSections.scrollSpeed = 0
         
  # launch animation for bottom right point
  @translatePointY
    point:      @base.segments[3].handleOut
    to:           0
    duration: durationNote: In my source code of the translatePointY  function, I added a deferred object for chaining, optional easing and  onUpdate function. It is omitted here for the sake of simplicity.In Conclusion
Last but not least, a class for the sections has to be added. Of course, you can make as many instances of it as you like; you just need to define initial Y offset and colors. Also, you will need to make sure that the section in your layout has the same height as the section in canvas. Then we can just applytranslated3d to both on the scroll  event and animations. This will cause HTML sections to move properly,  just like the canvas sections, and hence produce a realistic animation.
The reason why we need to use
translate3d instead of translateY  is to make sure that Webkit rendering engines use hardware acceleration  while rendering them, so we do not drop out of the 60fps animation  budget. But keep your eyes wide open if your sections contain any text.  3D transforms will drop anti-aliasing from subpixel to grayscale, so it  may look a bit blurry! 
 































