Top dweets of all time

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: #Food

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tomxor

function u(t) {

eval(unescape(escape`𩡯𬠨𨰮𭱩𩁴𪀦👙👚👩🐷𩐴𞱩𞱓𚰽𦀬𠰫👙𛁔𚰽𦠩𚀱𚱓𛰲𜑞𠰯𜐸𧡔𛰱𝠩𙐱𝑼𯀨𦀽𦐬𦐽𦠬𬠽𭑛𪰽𦱾𤰬啓𛁾𥁝𧑼👚👓𚡴𙐲𛐱𛀭𛑩🠴𩐴🱩𙐶🱵𦱫𧐫𚰺𤰽𠰽𥀽𜐸𝀺𮀮𩡩𫁬𤡥𨱴𚁘👩𙠲𝐵𛁙👩🠾𞀬𞀯𚀸𚱲𛱴𚐬𦠽𜐬𤰽𠰽𥀽𜐲𞀬𦀽𦀯𤰭𜐬𦐯👓𚐩`.replace(/u../g,'')))

Dec 9 2024 12:16 PM UTC

}// 140/140

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Photon-Mapping using a Random-March Scattering Model

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u/tomxor

A (very inefficient) physically based renderer in a Dweet! :) Give it 5 mins for reasonable convergence, the longer the better, Firefox is fastest. I know this is not the most interesting visually, but I found it challenging to make, and didn't fully understand the result. So the following hand wavey write-up is more of an analysis as I attempt to understand what's going on. I am not a PBR expert so I probably don't know what I'm talking about.
u/tomxor

This approach conceptually follows Photon Mapping, where light rays are forward traced, bouncing around the scene recursively, accumulating radiance into a spatial map on each bounce. Essentially painting reachable surfaces with light. Separately a ray for each pixel is cast into the scene to retrieve the current radiance for the position it intersects. From here, implementation deviates substantially from the original algorithm. Rays are marched. The map only stores irradiance, and uses spatial hashing instead of a kd-tree. However the most interesting differences are in surface interactions. BSDFs are the standard abstractions for reflectance and transmission but they are far too large to implement. Through "experimentation", AKA messing around on Dwitter, I found a roughly Lambertian reflectance distribution to emerge from a simple random march. Lambertian meaning a perfectly diffuse surface, which causes uniform propagation through 3D space, but a necessarily non-uniform distribution of reflected angles (this is worth taking some time to understand separately if it's not immediately intuitive).
u/tomxor

With ray marching each intersection naturally ends up embedded in a surface. Instead of correcting this, a new direction is randomly chosen and the ray is sent on it's way. Depending on the surface intersection depth and angle of reflection there is a chance the ray will escape (reflect) or remain trapped (absorbed). With the chance being greatest when reflecting in line with the surface normal, and lowest when parallel to the surface. Note how the surface, depth, and reflection ray form a right-triangle. For the reflection ray to escape, the depth must be less than cos(θ) at a step size of 1. Therefore assuming a uniformly random depth between 0 and 1, the reflectance distribution follows Lambert's cosine law. Additionally unlike a BSDF this provides random absorption for free, but with the disadvantage of reflectance distribution and absorption rate being inextricably linked. Another significant difference is that BSDFs are a statistical abstraction designed to extract the most value from each ray by modulating its radiance, representing many photons; whereas this model effectively represents a single photon for each surface intersection. Absorbed rays are thrown away rather than modulated, and each irradiance accumulation is an integer increment. The implication being the random march requires far more rays to converge because each ray has a binary existence and intensity like a photon, on the other hand each intersection is far simpler computationally compared to BSDFs.
u/tomxor

There are a few more gnarly details that complicate this. For simplicity I suggested trapped rays are immediately absorbed, which is possible, but it's simpler to allow them to rattle around a bit. This "widens" the reflectance distribution and increases overall reflectance, to a degree depending on how many consecutive intersections are allowed. But it also changes the overall behaviour by producing a slight Subsurface Scattering effect like skin or paper. Surfaces soften and glow as rays traverse, and weak points like corners diffuse as some rays tunnel through. Secondly, rays with a higher angle of incidence (ωi) have a lower max surface depth, yet the reflectance step length is unaffected. This difference distorts the reflectance distribution as ωi increases. When (ωr < ωi) escape is certain, and when (ωr > ωi) the chance abruptly returns to cos(ωr)/cos(ωi). i.e min(1, cos(ωr)/cos(ωi)). At ωi=0 the distribution is perfectly Lambertian, and at ωi=π/2 it is unnaturally uniform in angle. AFAIK this is not a physically realistic reaction to ωi. It almost resembles Fresnel reflections, where transmissive surfaces reflect more at grazing angles. However Fresnel is anisotropic, like a mirror. Yet here the distribution is centered around the surface normal. This is still a simplified analysis, it ignores subsurface marching, and how adjacent ωr and ωi share pseudo random variables (see below). The chaotic nature and compounding biases means an accurate distribution can probably only be obtained empirically.
u/tomxor

Finally, the ray step/direction vector, must be randomised upon each intersection. Initialising random unit vectors takes a lot of code, so there's a few tricks going on here, but these tricks also affect the result and noticeably compromise accuracy. Rather than a unit vector I've settled for a point in a cube, where the length is anywhere between 0 and 1. This actually helps convergence by randomising depth at repeat surface intersections, however the cube shape results in non-uniform propagation so distance based shading of all the axis aligned surfaces looks a bit too flat. Doing this three times still takes a lot of code, so only Z is randomized upon each intersection, and is then reused by cycling through the XY components, which provides a pretty bad but not-terrible distribution, apparently making it harder to reflect into corners. Z's randomisation combines t with one component of the ray position, so it is effectively a kind of feedback PRNG derived from the very scene geometry the randomness is being used to traverse, which I find kind of neat.
u/Joachim

Insane! Looks sooo realistic :0
u/fentbiggesthater

wow just came back from my vacation in saudi arabia. im now back in my 10m penthouse in new york and this is the first post ive seen after coming back that has genuinely impressed me. good job!
u/UEZ

Very impressive - well done! How can I understand: k = [~S, ~C, ~v], u[k] |= Z. Array u refers to what? Associative arra? Thx.
u/tomxor

Thanks. u is the dweet function which I'm exploiting as a predefined object for the spatial map. The purpose of bitwise inverting ~ each component is to obtain a floored version of the ray position (that it happens to invert doesn't matter) e.g [~0.1,~1.2,~2.3] = [-1,-2,-3], and importantly all positions between [0,1,2] and [1,2,3] will result in [-1,-2,-3] i.e it is binning positions into an integer grid. When passed as a key to u this is coerced into a string to become '-1,-2,-3'. The idea is to count photon intersections into each grid cell with u[k]++ as a kind of frequency based irradiance, but as an object each cell must be initialised before incrementing, so u[k]|=Z uses bitwise again to coerce all values into an int, ORing with Z will convert undefined values to 0, and existing integer values will be unaffected because Z is always less than 1.
u/UEZ

Thanks tomxor. The math / physics behind is too high for me ^^. My question is more related to understand JS what u[k] is. k is an array which is passed to u. When k=[10, 20, 30], what is the result in u[k]++?
u/magna

u/UEZ The property accessor [key] coerces key to a string. So, when you do obj[a] and a is [1,2] it will be obj['1,2'] because [1,2].toString() implicitly called.
u/magna

u/tomxor Another epic one!
u/UEZ

Thx magna :-) More or less what tomxor wrote. Just for my understand, does u[k]++ mean, when k=[1,2,3], u is u['2,3,4']?
u/fentbiggesthater

hm coll
u/tomxor

I think you're getting hung up on the array like key notation, but it's not being used as an array. Think of -1,-2,-3 as an abitrary property name on an object, the u.-1,-2,-3 property syntax would be equivalent if not for the invalid chars. u[k]++ simply increments a number stored for the property k, ++ only works because that property value has been previously initialised using u[k]|=0 which will convert undefined values to 0.
u/jellyedwards

Holy crap! They need to add a dwitter category to the Nobel awards for stuff like this!
u/0x61

[insert image of dribbling cat] We're not worthy. This is endgame
u/KilledByAPixel

https://www.reddit.com/r/tinycode/comments/1…
u/joeytwiddle

#stochastic #lighting #d3
u/ximavus

Awesome but my laptop is lagging with it (its like 1Ghz CPU so yea)

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tomxor

function u(t) {

eval(unescape(escape`𩡯𬠨𨐽𤰨𭀩𛁢👃𚁴𚐬𤠽𭰽𨰮𭱩𩁴𪀦👩🐸𜰲𜀻𪐻𦁼𦐪𜡼𥀯𜱼𚁡𚡘𚱢𚡔𛑢𚐪𚠲𚰨𚁢𚡘𛑡𚡔𚱡𚱡𚐪𚠲𚱙𚡙𛐮𜠩𚠪𜠼𛠰𜠿𥀭𤠿𮀮𩡩𫁬𤡥𨱴𚀭𛑩𙑷𛁩🠾𝰬𚁘𚱙𚱔𚐯𝀬𥀽𤠽𜐩𞡒𛐽𛠱𞡔𛑒🱔𛰽𛠹𝠺𥀽𤠯🐮𞐸𚑘👩𙑷𛰶𝀪𤠭𥀬𦐽𪐯𭰯𝠴𚡒𛑔𛰲`.replace(/u../g,'')))

Oct 21 2024 7:08 PM UTC

}// 140/140

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Shadownut

Show more comments…
u/vain

holy shit. how? simple mindblowing! 💗
u/magna

DAMN.
u/lewdev

This is insanity!
u/KilledByAPixel

Wow!!
u/tomxor

Thanks. Same shadow + global illumination technique as d/28068 just exchanged the scene and texture for a moving torus.
u/cantelope

excellent!
u/jellyedwards

Absolutely amazing!!
u/magna

"just exchanged the scene and texture". EZ.
u/tomxor

u/magna to be fair I started this one over a year ago, but couldn't quite fit it, so kept revisiting and shaving a char here and there, and eventually reconfigured the scene enough to find a combination that fit.
u/aleamb

wow!!

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KilledByAPixel

remix of d/26735 by u/KilledByAPixel

function u(t) {

eval(unescape(escape`󩭯󬬨󥜽󜼷󜜬󦬽󜭥󜼬󪜽󜌻󪜼󦬻󭌫󟜫󚽩󙝕󟼰󞬷󚝸󛭦󪝬󫍓󭍹󫍥󟝠󪍳󫌨󙍻󭌪󞜫󥌯󝍽󛌹󞜥󛌤󮽩󟽔󙜹󝼭󬜪󬜪󜬹󞬰󯜥󛌤󮽩󚼮󜝽󨌬󬜽󭌥󝌬󤜽󦬪󚍴󟬾󜬩󛍔󟝩󚭑󙝕󚭱󛍸󛭦󪝬󫍒󩝣󭌨󪜦󙭕󚽑󙜹󜜷󚽔󚭓󚍩󚜬󪜦󙭕󚽑󙝕󚽔󚭃󚍩󚜭󬜪󥜫󬜪󬜪󥜬󮬽󪜿󬜪󝜫󝌺󦬬󮬩`.replace(/u../g,'')))

Dec 31 2023 8:45 PM UTC

}// 140/140

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Happy new year! 🥳 #fireworks

u/Joachim

That's cool
u/Odog8

so cool! happy new year!
u/vain

Wow, so fucking cool. Great fx and colors. ❤
u/KilledByAPixel

thanks! i've been saving this one for a while ;)

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KilledByAPixel

function u(t) {

for(c.width&=i=w=8320;i--;x.fillRect(64+22*S(j=i/1324+t/9)+44*S(2*j)-q/2,39-29*S(i/441),q,b?-q:w))q=(b=i%320)&(z=i+1e3*t)%w<490&z%99<50?3:.3

Jun 20 2023 11:10 PM UTC

}// 140/140

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Roller Coaster 🎢

u/rodrigo.siqueira

Incredible! See also the train by u/jylikangas , 2018: https://www.dwitter.net/d/7702
u/Xen

love it!
u/magna

Wheee!

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danny@hille.dk

remix of d/21523 by u/danny@hille.dk

function u(t) {

w=c.width=128;for(i=1e4;i--;)x.fillRect(X=i%w,Y=i/w|0,Math.min(s=Math.hypot(X-64-
C(t)*40,Y-36-S(t*1.2)*28)/16,.4/((X^Y)%7)),s)

Jun 2 2023 9:45 PM UTC

}// 127/140

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bump mapping remix

u/Joachim

Really nice #lighting
u/@noel

Beautiful. I need to dig into this, to understand how this actually works.
u/rodrigo.siqueira

Wow! Replace X^Y with X|Y to generate Sierpinski triangles. Replace Math.min with Math.max for a more dramatic effect. Remove |0 for improved golfing (a minimal visible effect on top alignment). Replace "t*1.2" with "C(i+t)*6" for the "water effect".
u/jellyedwards

Wow that's amazing!!

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joeytwiddle

remix of d/27386 by u/joeytwiddle

function u(t) {

eval(unescape(escape`景爨椽挮睩摴栽ㄸ㐻椭ⴻ⥸⹦楬汒散琨㤰⬨∬㄰㔶㜻䐽㨼㬼䐾㰻㨸䑂㠶㐱㡀ㄯ⸱⼳㘿㝀剄䱛㴿慒呣䄼䡍假䄷㽄䭄䀵㩦䕃愹㥅䍆䜿㡉屜屜繊㡄繞繕㘹坶晗∮捨慲䍯摥䅴⡩⤭㌲⤪匨愽椭琩⼳ⰵ⭩ⱗ㴱⭃⡡⤬圩`.replace(/u([^D].)/g,'$1%')))

Apr 20 2023 6:04 PM UTC

}// 140/140

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M3DCotGLB

u/joeytwiddle

Minor refinement: Larger resolution so the dots are less noisy; linear index rather than sqrted.
u/deobfuscate

Now its ten times easier to see that its a meditating buddha.
u/Odog8

Holy crap
u/Xen

madness!

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taupelink

remix of d/24370 by u/taupelink

function u(t) {

eval(unescape(escape`景爨洽㘰〻堽ㄫ匨㐪洩ⱙ㵓⠷⩭⩭ⴭ⤻砮晩汬剥捴⠱攳⩘ⰸ㄰ⰲ⩩⩃⡭⭩⩴⤯⠱ⵙ⤯㈪⩴⨨䌨太天㸰⤬太洪㈯㌪⩴⤩椽津ㄲ〫㈰ⱸ⹦楬汓瑹汥㵒⡩⼲⨪夬椪㴮㘫匨堫太琩⽴Ⱪ⨽ㄭ夯琪⩴Ⱞ㔫䌨津琩⼳⤠`.replace(/u([^D].)/g,'$1%')))

Jan 11 2023 6:52 AM UTC

}// 139/140

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d/26815

u/Xen

nice!
u/tomxor

That's crazy!
u/magna

WOW

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danny@hille.dk

function u(t) {

for(X=w=c.width=180;X--;)for(Y=98,p=.5*((C(t/3)*Y)**2+(S(t/4)*X)**2)**.5;Y--;)X-t*60&Y-t*60&23&&x.fillRect(X+S(t+Y/55)*p,Y+C(t+X/44)*p,1,1)

Jan 3 2023 12:49 AM UTC

}// 139/140

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remix of https://twitter.com/toshiyamarukubo/status/1…

u/danny@hille.dk

¡dn ǝpıs sıɥ⊥
u/vain

Incredible cool 3d looking fx. love it
u/joeytwiddle

Impressive! #sierpinski #flag

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tactical_retard

remix of d/25761 by u/rodrigo.siqueira

function u(t) {

eval(unescape(escape`󮜽󭌿󮜫󤼨󮜪󝼫󭌩󚬳󞬹󞜊󩭯󬬨󪜽󜭥󜼻󪜭󛜻󮌮󩭩󫍬󤭥󨽴󚍴󚬲󜼰󛍩󛌹󞜬󜜩󚝻󠬽󪜼󮜪󝬊󠜽󝌹󚽔󚍩󚭹󚼲󚜊󢜽󛬵󚽩󛼱󜌸󚽓󚍴󚜫󚌱󚽃󚍴󛝩󛼵󜌩󚜯󜬊󪌽󚌱󚽓󚍉󛼱󛬱󚜩󛼲󒭈󟜨󜜫󤼨󢜫󜼩󚜯󜬊󮌮󩭩󫍬󤽴󮝬󩜽󠬿󤬨󠜪󜜮󜬬󠜪󪌫󮜪󢌬󠜪󢌫󮜪󪌩󞭒󚌩󯜻`.replace(/u../g,'')))

Jul 1 2022 10:10 PM UTC

}// 138/140

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#aurora #mountains

u/vain

Now its just perfect! Incredible work!
u/tactical_retard

183 y=t?y+S(y*7+t)*3:99;for(i=2e3;i--;x.fillRect(t*230,i,99,1))A=49+T(i*y+2),I=.5+i/108+S(t)+(1+C(t-i/50))/2,h=(1+S(I/1.1))/2,H=(1+S(I+3))/2,x.fillStyle=i<y*6?R(A*1.2,A*h+y*H,A*H+y*h):R()
u/magna

So pretty!

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KilledByAPixel

remix of d/25270 by u/KilledByAPixel

function u(t) {

for(w=c.width&=i=s=10368;i--;x.fillRect(i%w,i/w|0,u[i]=(t-Math.hypot(i%w-64,i/w-36)/19)%16&2**(u[i+w]+2*u[i-w]+4*u[i+1]+8*u[i-1])?1:0,-1));

May 6 2022 3:58 PM UTC

}// 139/140

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Demake of Feedback Crystal by SPACEFILLER https://www.fxhash.xyz/generative/542 #fxhash

u/CaptainMeat

the talent
u/katkip

wow