Top dweets by u/pavel

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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Current theme challenge: #Opposites

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pavel

function u(t) {

for(c.width=120,k=4072;j=--k>>6;x.fillRect(60+i,j,1,1))i=k%64-32,s=64*j-i*i-j*j,f=s**.5*S(a=S(3*t))+i*C(a),x.fillStyle=R(g=f*f/4,g,g+f,s/99)

Mar 3 2019 3:17 AM UTC

}// 140/140

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u/aleamb

#shading
u/13thptr

#sphere

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pavel

function u(t) {

for(j=t?1e3:a=b=0;j--;x.fillRect(960+450*a,540+450*b,1,1))s=Math.random()<.5?-1:1,A=(Math.hypot(a,++b)+a)/2,b=(b<0?-s:s)*(A-a)**.5,a=s*A**.5

Feb 13 2019 9:09 PM UTC

}// 140/140

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IFS #julia attractor for c=i. Play with adding different constants to a and b in the Math.hypot call

u/pavel

a+=.123,b+=.745 is called Douady's rabbit fractal
u/katkip

How! Amazing
u/13thptr

#fractal

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pavel

remix of d/11455 by u/pavel

function u(t) {

for(r=c.width|=0;--r;)x.stroke(p=new Path2D,p.arc(960,540,r,a=(r+~~(99*t)-t/9)*5**.5/2%(2*Math.PI),a+(x.lineWidth=32)/r))

Dec 19 2018 1:13 AM UTC

}// 121/140

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Black Hole

u/pavel

Deleting %(2*Math.PI) works in Chrome but not in Safari.
u/pavel

Notice that the radius does not change with time. The inward motion is achieved by drawing a smaller radius square next to where the larger radius square was a frame ago.
u/pavel

If the squares were numbered you'd see that the numbers jump around every frame.
u/pavel

I've made an explanation dweet d/11488

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pavel

remix of d/11426 by u/Quant1um

function u(t) {

t?w=c.width|=onclick=e=>{i+=e.x/7-X/s,j+=e.y/7-Y/s}:s=i=j=X=Y=20
x.fillRect(X+=i*=(i<0?X>0:X<w)||-.7,Y=++j+Y>1e3?(i*=.9,j*=-.7,1e3):Y+j,s,s)

Dec 16 2018 3:34 AM UTC

}// 140/140

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pavel

remix of d/24072 by u/BackendForth

function u(t) {

for(i=c.width|=0;i-=8;)x.arc(X=960-99*S(t+=.03),540+i,200+i/8,2,8)
x.fill()
h=21*S(t+C(t))
for(j=2;j--;)x.clearRect(X-50+99*j,529-h,11,2*h)

Oct 11 2021 10:31 PM UTC

}// 139/140

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u/BackendForth

Nice! The blinking makes it much more life-like . . . unlife-like?

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pavel

remix of d/21217 by u/tomxor

function u(t) {

c.style='filter:invert(';for(i=9;i;X-=C(a),Y+=S(a))u++<2e3?(X/49^Y/49+42)%15>1?x.fillRect(X,Y,.2,.2):a=u*t:X=540+--i*S(a=u=t/i,Y=540+i*C(a))

Jul 3 2021 7:06 PM UTC

}// 140/140

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pavel

remix of d/20898 by u/cantelope

function u(t) {

for(c.width=i=640;i--;T=!T&&!x.beginPath(x.stroke()))j=i/16-T*i&30,r=(j+4)/12<<6,x.arc(320+r*C(a=j/1.91+t),180+r*S(a),i&30?0:32,0,7)

Dec 4 2020 3:01 AM UTC

}// 132/140

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Metatron's Cube

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u/pavel

Golfed this one a little bit :) #symmetry
u/pavel

i=[4 bits for start circle index][4 bits for end circle index offset from start circle][1 bit to decide start vs end]
u/pavel

That's 2**9=512 which is too small for power-of-two circle sizes but start clicle index wraps around so larger i is only redundant.
u/pavel

end-circle-offset == 0 is easy to check and means start and end are same circle, so draw that circle.
u/pavel

Otherwise draw the current circle with radius 0 which is same as lineTo.
u/pavel

T=!T&&!x.beginPath(x.stroke()) starts/strokes the path every two circles.
u/pavel

Here is a version before all the bit hacking for(c.width=640,i=16;i--;)for(j=16;j--;x.beginPath(x.stroke()))for(k=2;k--;)q=(i+j*k)%16,r=((q+2)/6|0)*64,x.arc(320+r*C(a=Math.PI/3*q+t),180+r*S(a),!j*32,0,7)

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pavel

remix of d/20106 by u/pavel

function u(t) {

with(x)for(c.width|=j=32,translate(960,r=540),a=t/=7;j--;scale(s=1/2**.5/S(t%1.571+.785),s))rect(-r,-r,2*r,2*r),rotate(a=-a);x.fill`evenodd`

Sep 26 2020 3:09 AM UTC

}// 140/140

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Squares all the way down #2

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pavel

function u(t) {

c.width|=f=(X,Y,r=Y,i=r>9&&3)=>{for(x.fillRect(X,Y,s=r<10&&12,s);i--;)f(X+r/2*C(a=23*i+t*C(i)),Y+r/2*S(a),r/2)}
f(960,540)

Mar 27 2020 6:17 AM UTC

}// 122/140

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Why can't you just be normal #sierpinski ?

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u/pavel

I have no idea why this works. I was messing around with something else and then a sierpinski triangle popped out and started spinning around...
u/xem

love the explanation ^ :D
u/katkip

nice
u/pavel

I think I figured it out. If you set s=12 the structure becomes more apparent. +t*C(i) doing SO MUCH WORK is an amazing accidental find.
u/pavel

This certainly looks like a 2d projection of something 3d, how to get the depth information?
u/pavel

The trick is to rng three 2d vertices and smoothly vary them. Every combination uniquely maps to a valid 2d projection of a 3d plane so our brains infer the 3d shape.
u/pavel

for(c.width|=i=3;i--;x.lineTo(960+500*S(i*t),540+500*S(i+t)));x.fill()

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pavel

function u(t) {

for(i=36;--i;x.fillRect(m?Math.abs(9*t%53-26)<<6:i*60-210,m*i*327,60<<2*m,m?99:2e3))m=i<3,x.fillStyle=m?i%2?'#ff0':'#00a':i%2&t/4?R():'#eee'

Feb 9 2020 1:50 AM UTC

}// 140/140

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Stepping feet #illusion

u/katkip

#opticalillusion
u/veubeke

@pavel Sorry, I didn’t see your dweet. I deleted mine and will do a better job searching next time.
u/pavel

I was just cross-posting mine as they were on the same topic without a clear keyword. You should have kept yours, it was clearly different.

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