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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pavel

function u(t) {

for(c.width=640,i=8;i--;x.stroke())x.beginPath(r=150*2/3*(i>1)),x.arc(320+r*C(a=Math.PI/3*i+t),180+r*S(a),150*(i?1/3:1),0,7)

Jan 4 2020 9:07 PM UTC

}// 124/140

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d/17063 #explanation

u/pavel

If you take every point on this picture, turn it into z=x+i*y and feed it through (sqrt(3)+z)/(1+sqrt(3)*z) then decode the resulting complex number as (x', y') and put a point there, you will get d/17063.
u/pavel

Of course you can't take infinitely many points so you will get a pixelated version. To get a proper version you need to solve the equation for the new, mapped, circle given the old circle so that you can use x.arc..

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pavel

function u(t) {

for(c.width=960,p=Math.PI,r=270,k=64;k--;)for(r*=k%2||C(d),n=j=k%2?7+k>>1:99;j--;x.arc(480,270,r,a=2*d*j-p/2,a))d=p/(n-1)
x.fill`evenodd`

Jun 29 2019 11:20 PM UTC

}// 137/140

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Vertex sphere

u/pavel

Based on Mathologers shirt: https://www.youtube.com/watch?v=O1sPvUr0YC0
u/KilledByAPixel

👍
u/Xen

oooooo nice
u/pavel

With more layers the middle circle does not shrink to nothing, it asymptotically approaches about 11% of the radius

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pavel

remix of d/14376 by u/pavel

function u(t) {

t?x.arc(w=960,h=540,h,0,c.width|=0):X=Y=1e3
X*X+Y*Y>2.4e5&&(r=C(t*t)*8+12,U=-X/r,V=-Y/r)
X+=U;Y+=++V;x.arc(w+X,h+Y,5*r,0,7);x.fill`evenodd`

Jun 6 2019 5:00 AM UTC

}// 139/140

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#physics #bounce updated so ball size reflects speed

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pavel

function u(t) {

for(c.width|=p=300;e=p--**.9%1;x.fillRect(960+r(0)/z,200+99/z,s=9*e/z,s))r=d=>p/(1+e*C(a=t/4+p))*C(a+p+d)+2*p/(1/e-e)*C(p+d),z=.5+r(1.6)/800

Feb 28 2019 6:54 AM UTC

}// 140/140

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Galaxy

u/pavel

300 bodies which individually only interact with an infinite mass at the center
u/pavel

Each body moves around an ellipse, the orbits are accurate. However, the movement speed is a very rough approximation.
u/pavel

Naively drawing an ellipse centers it around one of the focal points, however moving a body on this path slows the body down near this focal point and speeds it up near the other one.
u/pavel

The opposite effect is needed. So this code still moves a body around an ellipse but it re-centers the ellipse on the 'other' focal point.
u/pavel

In polar coordinates the difference between the x and y coordinates is a phase shift of pi/2 ~ 1.6

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pavel

function u(t) {

for(c.width|=i=99;S[u[t]=t]=x[t]=i--;x.fillRect(960+(u[i]+=S[i]-=u[i]/d),540+(x[i]+=C[i]-=x[i]/d),C[t++]=9,9))d=(u[i]**2+x[i]**2)**1.5/7e3

Feb 28 2019 5:17 AM UTC

}// 138/140

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#physics #orbit #orbits

u/pavel

Funky start due to lack of chars but quickly settles. Imagine a black hole in the middle.

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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/11463 by u/cantelope

function u(t) {

with(x)for(c.width|=i=6,scale(9,9),q=C(4*t);i--;stroke(),fill())moveTo(X=64+17*i,0),arc(X-60*S(a=(q>0?i:i-5)?0:q),60*C(a),8,a-Math.PI/2,9)

Dec 18 2018 12:32 AM UTC

}// 138/140

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u/cantelope

ah! of course. i knew there had to be an easier way ;P
u/katkip

Haha nice
u/iverjo

#newtonscradle
u/pavel

For a more realistic look replace (q>0?i:i-5)?0:q with (q>0?i:i-5)?q/50:q

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pavel

function u(t) {

for(c.width|=i=23,x.globalAlpha=.1;j=99*(i-->>1);x.fillRect(-j,0,2*j,99))x.setTransform(u=-C(a=(i%2-t/3%1)*1.57),v=S(a),0,1,960+j*v,j/2-j*u)

Dec 4 2018 12:21 AM UTC

}// 140/140

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#pyramid

u/pavel

Messing around with setTransform

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pavel

remix of d/10477 by u/pavel

function u(t) {

s=3+15*t%6;i=960-s*365;j=s*210;for(c.width|=a=n=0;n<1e4;T=n=>n&&T(n>>1)-n&1)T(n++)?x.lineTo(i-=s*C(A=a++*355/339),j+=s*S(A)):a-=3;x.stroke()

Nov 6 2018 4:56 AM UTC

}// 140/140

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#koch #fractal

u/13thptr

#zoom #loop

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pavel

function u(t) {

for(X=7;X--;)for(Y=4;Y--;)for(i=4;i--;x[i+q&1?'clearRect':'fillRect'](135*(1+2*X-r),135*(1+2*Y-r),r*=270,r))q=2*t+X+Y,r=(i+q%1)/4

Apr 16 2020 4:31 AM UTC

}// 129/140

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https://www.reddit.com/r/loadingicon/comment…

u/Xen

that q=t*t+X+Y tho ;-)
u/rep_movsd

#underrated

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