New #circlechallenge dweets

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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rep_movsd

function u(t) {

t?x.fillText(0,960+X/8,540+Y):Y=X=99
X+=(Y-=X/69)

Nov 6 2021 10:24 AM UTC

}// 49/140

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Almost a circle #circlechallenge

u/rep_movsd

Based on the Minsky algorithm
u/rep_movsd

48 bytes - t?x.fillText(0,960+X,540+Y):Y=X=99 X+=(Y-=X/9)/9
u/joeytwiddle

TIL, thanks! https://news.ycombinator.com/item?id=15266331

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rep_movsd

function u(t) {

[P,Q]=t?[A,B]:[0,1]
x.fillText(0,99*(B=Q*.8-P*.6)+960,99*(A=P*.8+Q*.6)+540)

Nov 5 2021 9:00 AM UTC

}// 75/140

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Circle2 #circlechallenge

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u/rep_movsd

This is based on an algorithm from "Electron Graphics and Sound" I read as a kid
u/rep_movsd

This is based on an algorithm from "Electron Graphics and Sound" I read as a kid
u/rep_movsd

We calculate a sine and cosine of a small angle delta initially, and thereafter derive them using trig identities using only addition and multiplication
u/rep_movsd

It so happens that C(O) and S(O) are almost exactly 0.8 and 0.6 for some O
u/rep_movsd

I found those by for(N=0.1;N<1;N+=.1) M=(1-N*N)**.5,console.log(N,M)
u/rep_movsd

Can be 67 bytes
u/rep_movsd

Can be 67 bytes
u/rep_movsd

[P,Q]=t?[P*.8+Q*.6,Q*.8-P*.6]:[0,1] x.fillText(0,99*Q+960,99*P+540)

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rep_movsd

remix of d/24281 by u/danny@hille.dk

function u(t) {

x.fillText(t?O=500:Y=X=300,O+X,O+Y)
X+=Y,Y-=X,X+=Y*.99

Nov 5 2021 8:04 AM UTC

}// 54/140

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Circle #circlechallenge

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ArthurThuczsec

function u(t) {

t?x.fillText(9,0,3):c.width=5

Nov 4 2021 5:23 PM UTC

}// 29/140

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#circlechallenge

u/rep_movsd

c.width=99,x.fillText('O',45,29)
u/donbright

lol nice

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magna

function u(t) {

R=540,Y=R-t*99
for(s=0,d=-1;s<=R*R-Y*Y;s+=d+=2);
X=d/2
x.fillRect(960-X,R+Y,X*2,1)

Nov 2 2021 10:36 PM UTC

}// 82/140

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#circlechallenge No trig, no direct square root: Just using the Pythagorean theorem + the fact that sums of odd numbers give perfect squares

u/Xen

very clever sir

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donbright

function u(t) {

限=199
for(m=-限;m<限;m+=(2+t))for(n=-限;n<限;n+=(3+t)){
g=2*m*n
b=m*m+n*n
r=m*m-n*n
x.fillRect(1920/2+frame*g/b,1080/2+frame*r/b,1,1)}

Nov 2 2021 3:12 PM UTC

}// 130/140

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As part of #circlechallenge I go back to the old rational parametrization of the circle from Wildberger's "chromogeometry", which has elements of Euclid. Each frame draws rational points on a circle, and each frame the radius gets bigger. All of the patterns are a kind of optical illusion.

u/donbright

changing '2' and '3' to different numbers will give different patterns

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cantelope

function u(t) {

x.fillRect(960+((b=t?b:[0,h=520,h/22.7,0])[0]+=b[2]),h+(b[1]+=b[3]),9,9,b[2]-=b[0]/h,b[3]-=b[1]/h)

Nov 2 2021 12:30 PM UTC

}// 98/140

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#circlechallenge (no sine/cosine)

u/donbright

does fillrect have 6 parameters here?
u/cantelope

heh. it only looks at the first 4. i'm not actually saving any space by including 6 parameters, but why not? :)
u/cantelope

can you see how this circle method works? there is an array with 4 elements, the first 2 being positions (x,y), and the last 2 being analogous to a vector (in physics) with magnitude and direction, or simply (velocity-x, velocity-y). The velocity vector is added to the position coordinates once per frame and is itself adjusted in a way to create a perfectly circular "orbit" about the origin. Interestingly, this approach can be extended into 3 or more dimensions, and involve, obviously, more than 2 bodies. 3-body orbital chaos can be very interesting and beautiful, e.g. https://code.dweet.net/full/2w8z

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pavel

function u(t) {

t?0:X=Y=360
X-=Y>>4
Y+=X>>4
x.fillRect(960+X,540+Y,9,9)

Nov 1 2021 8:52 PM UTC

}// 55/140

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Minsky circle algorithm #circlechallenge

u/cantelope

>>8 creates an octagon, strangely
u/donbright

awesome
u/rep_movsd

x.fillText(t?0:X=Y=360,960+X,540+Y) Y+=(X-=Y>>4)>>4 works too

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tactical_retard

function u(t) {

h=540
x.lineTo(X=960+C(k=t**t)*h,Y=h+S(k)*h)
x.moveTo(X,Y)
x.stroke()

Nov 1 2021 8:09 PM UTC

}// 69/140

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#circlechallenge

u/tactical_retard

55: h=540;x.lineTo(X=960+C(k=t**t)*h,Y=h+S(k)*h);x.stroke()

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rep_movsd

function u(t) {

t||(M=O=.018,N=P=.9998,r=540)
if(t&&t<3.1)with(x){for(i=200,K=t*r,beginPath();--i;lineTo(K*B+r,K*A+r))A=O*N+P*M,B=P*N-O*M,O=A,P=B;stroke()}

May 15 2021 10:22 AM UTC

}// 139/140

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Look Ma - no trig!

u/rep_movsd

#Circlechallenge

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