d/23806 figure 1 by taupelink

function u(t) {

c.width=1920 // clear the canvas
for(i=0;i<9;i++)
x.fillRect(400+i*100+S(t)*300,400,50,200) // draw 50x200 rects

} // 122/140

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    u(t) is called 60 times per second.
    t: Elapsed time in seconds.
    S: Shorthand for Math.sin.
    C: Shorthand for Math.cos.
    T: Shorthand for Math.tan.
    R: Function that generates rgba-strings, usage ex.: R(255, 255, 255, 0.5)
    c: A 1920x1080 canvas.
    x: A 2D context for that canvas.

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taupelink

function u(t) {

k=120;for(i=k;i--;)
f=i*t,X=f*f%16,Y=X*f%9,
x.fillStyle=R(q=i*2,q*=1+S(X),q*=1-S(Y)),
x.fillRect(k*X,k*Y,k/5**t,i)

Sep 7 2021 2:03 PM UTC

}// 114/140

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d/23806 figure 1

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u/taupelink

this week i will give a line-by-line description here in comments and then maybe in a blog post
u/taupelink

definitely a blog post. the comments will come over time...don't feel obligated to come back and check this dweet for new comments
u/taupelink

k=120: for code golfing purposes, this variable plays multiple roles: loop iteration count per frame, scale factor for X&Y coordinates, width of each rectangle at the start of the animation
u/taupelink

for(i=k;i--;): establishes a loop where i counts down from 120 to 1. "i--" means, If i is 0, then stop here; otherwise, decrement i by 1
u/taupelink

f=i*t,X=f*f%16,Y=X*f%9: this code creates quasi-random decimals X (0.0-15.999) and Y(0.0-8.999). (Hat-tip to whoever suggested this technique... u/pavel ?) If you multiply the upper bounds by 120 each, you get the overall dimensions 1920x1080.
u/taupelink

x.fillStyle=R(red,green,blue): sets the RGB color value for fills. I will take each component one at a time...
u/taupelink

q=i*2: sets the red component to 2x the loop index, i.e. an even number from 2 to 240. This covers most of the possible range 0-255. The red value is tied to i but not to X or Y; rectangles everywhere have a random degree of red.
u/taupelink

q*=1+S(X): sets the green component, and updates the value of q, to q*(1+sin(X)). Where sin(X) is close to -1, around X=1.5*pi and X=3.5*pi, the value of q is close to being zeroed out by this code; that explains the vertical red bands.
u/taupelink

q*=1-S(Y): sets the blue component, and updates the value of q, to q*(1-sin(Y)). This is why you see the green bands (no blue) around Y=0.5*pi and Y=2.5*pi; that's where sin(Y) is close to 1.
u/taupelink

x.fillRect(top,left,width,height): standard Javascript for drawing a rectangle. Again I will take one component at a time...
u/taupelink

k*X,k*Y: the X- and Y-coordinates of the upper left-hand corner of the rectangle, scaled by a factor of k.
u/taupelink

k/5**t: the width of the rectangle, which decreases exponentially over time. This can provide texture at different scales, including fine-grained detail.
u/taupelink

i: the height of the rectangle, equal to the index variable. The height of each rectangle is proportional to the red component, indeed to every component; so, for the 120 rectangles that are drawn in any given frame, some are tall and bright, some short and dark.
u/taupelink

A blog post on this dweet is up: https://medium.com/@taupelink/elements-of-a-…


      u(t) is called 60 times per second.
      t: elapsed time in seconds.
      c: A 1920x1080 canvas.
      x: A 2D context for that canvas.
      S: Math.sin
      C: Math.cos
      T: Math.tan
      R: Generates rgba-strings, ex.: R(255, 255, 255, 0.5)

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