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.

Try the new frontend: beta.dwitter.net
Current theme challenge: #Opposites

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pavel

function u(t) {

for(c.width|=f=g=>g(a=32*j**.5)*a*17,i=99;i--;x.fillText('💩',960-s/2-f(S),540+f(C)))j=(i-2*t%1)/99,s=75*Math.min(9*j,1,5-5*j),x.font=s+'px"'

Apr 16 2020 4:30 AM UTC

}// 140/140

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pavel

remix of d/13495 by u/pavel

function u(t) {

for(i=t?c.width|=C=_=>u[j=q+n&-n|p/n]=-!u[j]|1:p=q=r=s=571;i--;u[i]||x.fillRect(i?i%n*n:p+=r*=C(p+=r),i?i&-n:q+=s*=C(q+=s),z=i?n:15,-z))n=64

Apr 11 2020 10:31 PM UTC

}// 140/140

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#breakout

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u/pavel

Fixed the tilted look, the missing upper left block, and increased the size of the ball.
u/pavel

Why does changing 571 break the code for most values? :)
u/pavel

472, 582, 593 work well though
u/iznax

The code seems to work with most starting values if you change it to "C=_=>(p|q)<0?-1:u[j=q+n&-n|p/n]=-!u[j]|1" and handle negative coordinates as blockers?
u/KilledByAPixel

👍
u/pavel

Its shorter to init positions and velocities to same number but makes velocities too fast. Another problem is that init needs to happen once and shortest way to do that is t?<spot>:init which creates a spot to do something every non-first frame. I solve both problems by naming my collision detection function C and defining it on every non-first frame. On the first frame C is Math.cos so the velocity update code does r = r*C(p+=r) = 571*Math.cos(571+571) = 17.7 which is a reasonable speed.
u/pavel

The ball needs to be updated once per frame. Since I am iterating with a single index its easiest to check for index 0. This corresponds to the upper left block which is why it was missing in the original. A short fix is to shift everything up one block by using negative height for the blocks and adding a row to ball position encoding. The +n in q+n&-n|p/n.
u/pavel

I encode and decode 2d co-ordinates into one number. The block coordinates are (i%n,i/n|0) and their width is n making their real positions (i%n*n,(i/n|0)*n). Lets simplify the second one. If we choose n=2**k then (i/n|0)*n = (i/2**k|0)*2**k = (i>>k)<<k so we are zeroing out the last k binary digits. But if n=2**k then -n is a bunch of ones followed by k zeroes (https://en.wikipedia.org/wiki/Two%27s_comple…)! Therefore (i/n|0)*n = i&-n.
u/pavel

Need to check if ball pos (p,q) touches a new block. Ball is always in some block, find that blocks pos index. Dividing ball position by n gives the virtual coords and blocks are 1x1 so truncating gives 2d block coordinates (p/n|0,q/n|0). Want to encode this into index j where (x,y)=(j%n,j/n|0). Therefore j=(q/n|0)*n+(p/n|0). If n=2**k then in binary j=[32-k binary digits y-coord][k binary digits of x-coord] so we can use bitwise-or which also auto-truncates so j=(q/n|0)*n|p/n. And as we saw (q/n|0)*n=q&-n so j=q&-n|p/n! Real code uses j=q+n&-n|p/n to add one row to ball pos to account for shift up to hide missing (0,0)` block.
u/pavel

p+=r*=C(p+=r) encodes an unbelievable trick that is perfect for collision detection. For detection we need to independently try advancing vertically and horizontally, check for collision, and reverse course if hit. The temporary state involved in trying can cost a lot of chars. p+=r*=C(p+=r) does it all and C doesn't even read its argument! When C is invoked the global p it sees was already incremented by r. However, the outer p+= will eventually discard that increment. Magic!
u/rep_movsd

Un-effing-believable
u/hvianna

Wow, this is insane!
u/jylikangas

Masterclass in code golfing!
u/13thptr

awesome, looks like the ball escapes without breaking everything after a while though. will read the explanation more thoroughly.
u/pavel

No chars left for bounds checks! It freaks out with negative positions. If I find a way to shorten I will add bounds.
u/ersagun

I need to read and reread that explanation on a loop until I get this. This is incredible.
u/Qwitter

Just wow.

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pavel

remix of d/18153 by u/Kirjava

function u(t) {

with(x)for(beginPath([X,Y=X,r=200,a=2]=u[T=-~T]||[999]),fillStyle=R(i=4,3e3/r);i--;fill())lineTo(...u[2*T+i]=[X-C(--a)*r,Y+S(a)*r,r*.8,a-9])

Apr 7 2020 3:38 AM UTC

}// 140/140

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#tree #waitforit #uncompressed

u/pavel

This is a breadth-first traversal of a binary tree, one frame at a time. The tree is maintained in a 1D array (2n+i notation) that I simply iterate left-to-right. The loop does double-duty for drawing the current node and inserting the children. The shape has four corners so the loop runs four times and inserts four children: 2n+0, 2n+1, 2n+2, 2n+3. My mind was blown when I realized no extra code was needed to prevent the adding of the extra children because the first two children of the next iteration will overwrite them!
u/joeytwiddle

#broccoli
u/katkip

interesting
u/pavel

https://i.imgur.com/FZ9Whj4.png

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pavel

function u(t) {

for(c.width=i=640;i--;i&25&&x.beginPath(x.stroke()))X=i+t%1*32-320,r=i&1||-1,z=.8+r/9*S(a=X/69*S(t)),x.arc(320+X/z,180+36*r*C(a)/z,5/z,0,7)

Apr 5 2020 11:21 PM UTC

}// 139/140

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#dna coil

u/katkip

Smooth
u/sigveseb

Warping train tracks

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pavel

function u(t) {

for(c.width=i=620;i--;x.lineTo(310*(z+p*S(b))/z,300*(3+q*C(a))/z))q=i/8&1||-1,p=4-q*S(a=S(a=S(b=i/98+2*t)+b)/2+a/2),z=8+p*C(b-=t);x.stroke()

Apr 4 2020 7:12 PM UTC

}// 140/140

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#mobius strip

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u/pavel

Using sin(sin(x)+x)+sin(x)+x as a smooth staircase function to implement the flip as a pulse.
u/KilledByAPixel

👍
u/Xen

love it
u/aleamb

love it!
u/danny@hille.dk

Nice - möbius tape
u/Qwitter

Im sorry, but I find only one side of this to be Awesome.
u/vain

beautiful and smooth transformation / animation

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pavel

function u(t) {

for(i=1920;i--;x.fillRect(i&-T,i%T*T,T=32,T))x.fillStyle=`hsl(${T*t},99%,${u[i]=u[i]*.94+T/Math.hypot(i/T-T-C(3*t)*20,i%T-16-S(4*t)*9)||0}%`

Apr 2 2020 4:46 AM UTC

}// 140/140

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Flare

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u/pavel

Inspired by https://twitter.com/ntsutae/status/124366720…
u/jylikangas

Lovely use of an array for the trail effect!
u/BriSeven

hypot?! WHAAAT how long has THAT been there?
u/katkip

this is actually easier than it looks
u/sigveseb

Looks very pretty :)
u/aleamb

amazing!
u/rodrigo.siqueira

It reminds me the light and movement of this Fluid Simulation https://paveldogreat.github.io/WebGL-Fluid-S…
u/Scaledish

hell, it looks better than the fluid simulation
u/joeytwiddle

#glow #worm

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pavel

function u(t) {

f=(i,j=i%1,k=~~i,m=j*j*(3-2*j))=>S(k*k)*m---m*S(--k*k)
for(i=c.width|=0;i--;)x.fillRect(i,540+99*f(i/32+5*t),5,5)

Mar 28 2020 9:41 PM UTC

}// 113/140

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I would love to find a better / shorter 1D noise function #challenge

u/pavel

This one assigns a 'random' number to each integer k via S(k*k) and uses smoothstep to interpolate between them.
u/pavel

Another idea to play around with f=(i,n=9)=>n&&C(n**.5*i)/n+f(i,n-1)
u/joeytwiddle

#random

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pavel

remix of d/18074 by u/pavel

function u(t) {

c.width|=f=(X,Y,d,z=2+X*S(a=Y-4*t))=>d>>8?x.fillRect(960+1e3*X*C(a)/z,540+1e3*Y/z,6,6):[t,t+2,t+4].map(i=>f(X+C(i)/d,Y+S(i)/d,2*d));f(0,0,2)

Mar 28 2020 3:27 AM UTC

}// 140/140

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#sierpinski dance

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u/sigveseb

Very clean!
u/DataMeta

So smooth!
u/aleamb

wow! very smart code!
u/lionleaf

What an amazing dweet. And little did you know I had already planned #dancing as the theme for April. You were ahead of the times :D
u/joeytwiddle

Nice! Here is a dirtier, underrated relative: d/13611
u/Qwitter

looks glossy!
u/vain

Very nice and smooth 3D rotated and transformed sierpinski

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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) {

with(x)for(c.width|=i=4;i--;i%2||beginPath(fill()))fillStyle=R(r=150+90*S(a=t%3.14+(i>1)*22),r),arc(960-666*C(a),540,i%2*r,a/=2,a<.73?-a:19)

Mar 27 2020 5:41 AM UTC

}// 140/140

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#pacman #loop

u/aleamb

love it!
u/farter

poop eats
u/farter

*my poop eats me*

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