Dweets awesomed by u/corruptio

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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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…

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magna

function u(t) {

eval(unescape(escape`󩭯󬬨󮌮󩭩󫍬󤭥󨽴󚌰󛌰󛍷󟜲󩜳󛍩󟝷󚜻󪜭󛜻󦜼󞍼󦜾󜜱󯍘󟌸󯍘󟬲󝍼󦌦󜜦󙭸󛭣󫍥󨝲󤭥󨽴󚍘󚬵󜌫󤼨󭌩󚬳󜌰󚽍󛍙󚬵󜌫󣜬󝜱󛌵󜜩󚝘󟝩󙜵󜜭󝬬󦜽󪜯󝜱󯌰󛍍󟜨󚍓󚍴󚜫󜜩󛼲󚜪󚬹󚭙󚭓󚍴󚽘󚭙󚜻`.replace(/u../g,'')))

Sep 29 2023 5:09 AM UTC

}// 116/140

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tectonic #default

u/UEZ

nice
u/taupelink

cool!
u/danny@hille.dk

WOW! SOO COOL!!
u/aleamb

yeah!

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tomxor

function u(t) {

eval(unescape(escape`𩡯𬠨𨰮𭱩𩁴𪀽𜐹𜠬𤠽𝀸𛁩🐸𜀶𝀻𪐭𛐻𮀮𩡩𫁬𤡥𨱴𚁓𚰹𝠬𥀫𝐴𛁃𚁍𨑴𪀮𨑴𨑮𜠨𤰽𪐥𞐷𛑒𛁔👩𛰹𝰭𤠬𬠽𚁓𚡓𚱔𚡔𚐪𚠮𝐩𚠹𚐪𜠰𛑲𙠴𝀦𙡲🠳𝠿𬠼𝀲🱔𛱒𞡓𛱒𞠱𛁲🠳𝠿𬠼𤠺𮠨𜰩𛰵𚐩𮠽𫠽🡮𛐭𙠦𠰨𥀯𜠫𤰪𥀯𤠫𭀪𞐩𚡃𚁔𛰴𛑺𚁮𚐪𜠩𛑲𛰶`.replace(/u../g,'')))

Nov 13 2020 1:17 AM UTC

}// 140/140

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#stargate

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u/DataMeta

wow WHAT
u/DataMeta

super rad combo of that fluid/smoke technique from a while back and the recent 2.5D Doom texture tricks!
u/chris@grimtech.net

Is this an incoming or outgoing wormhole? thanks
u/magna

WHAT.
u/sigveseb

Holy smokes!
u/tomxor

https://news.ycombinator.com/item?id=25088683
u/aleamb

brutal! amazing!!!
u/rep_movsd

This is one of the all time greats
u/Xen

Yess!
u/UEZ

Awesome. One rookie question: where are the color values saved?
u/red-lady

Stargate!!
u/tomxor

@UEZ the width and height of fillRect are used, when less than one pixel it will interpolate the alpha channel in proportion to the area. The same happens when an edge lies between two pixels (anti-aliasing).
u/UEZ

@tomxor: thanks for your fast reply. :-) That's what I thought but when will width used, when height? I'm trying to under JS by converting it to FB.
u/UEZ

*understand
u/tomxor

The following are equivalent when the values of w and h are between 0 and 1: fillRect(0,0,w,h) == fillRect(0,0,w*h,1). This is because the alpha channel of this pixel value is roughly proportional to the subpixel area (w*h). In terms of the patern we are trying to create, multiplication it's like the continuous version of AND, i.e the binary version is 1 IF w AND h. Additionally a lot of characters are saved when separating into w and h because we dont need to wrap the actual subexpression used to create w and h in parens and multiply them i.e fillRect(0,0,(.1+.2)*(.3+.4),1) becomes fillRect(0,0,.1+.2,.3+.4), that's -5 chars!
u/UEZ

@tomxor: thx.
u/nystrand

epic!
u/jelmo

Nice
u/vain

Wow! This seems to be your stargate... Seems you are not from this world! Incredible!!!

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KilledByAPixel

function u(t) {

eval(unescape(escape`𩡯𬠨𭀿𨰮𫱵𭁥𬡈𥁍𣀽𫰺𪐽𫰽𙰧𞱩𚰫🀱𜀲𝀻𫰫👠🁣𫱤𩐠𫱮𨱬𪑣𪰽𭁨𪑳𛡩𫡮𩑲𢁔𣑌🐧𙁻𣐨𪐩🰧𚠧𞡮𯁼𙲷𙱽𙰾𘰼𛱣𫱤𩐾𙁻𪐥𝠴🰧𙰺𙰼𬀾𙱽𨀩𩡯𬠨𫠽𪠽𜀻𪠼𞐻𫠫👍𚁩𛐶𝐫𪠥𜰫𚁪𚰫𛰳𯀰𚐪𝠴𚐩𣐽𪐽🡩🠶𝀦𪐼𞐶𜀦𪐥𝠴🠱𙡃𚁩𚡩𚐾𛠹`.replace(/u../g,'')))

Jul 30 2020 6:37 AM UTC

}// 138/140

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Minesweeper 💣 #interactive #game

u/KilledByAPixel

hint - the sides are safe, there are 117 mines
u/Irratix

0_0
u/Xen

This is epic!!!
u/donbright

holy cow

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tomxor

remix of d/19547 by u/tomxor

function u(t) {

for(c.width=w=127,i=8e3;i--;t?p&T[r=t&2?i-w-r%3:i+w+r%3]<1&&--T[i]&++T[r]:T[i]=r%3)p=T[i],x.fillRect(X=i&w,Y=i>>7,1,p/3),r=i*t^Y/6&X/6

Jul 29 2020 11:41 AM UTC

}// 134/140

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#Serpinski #Hourglass v2

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u/tomxor

Removed the pseudo random left bias and made 1 bit, more sandy :)
u/tomxor

#sand #electric
u/magna

This is epic.
u/KilledByAPixel

amazing!
u/13thptr

incredible
u/13thptr

incredible
u/DataMeta

phenomenal #physics
u/Xen

lovejit
u/tomxor

Thanks u/KilledByAPixel for the original idea and implementation!
u/IV

ooh, you do the best stuff!
u/andrea270872

Wow!
u/donbright

these are incredible
u/joeytwiddle

Impossible! 🤩
u/vain

cool

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Kirjava

function u(t) {

eval(unescape(escape`𭁼𯀨𬰽𦰮𛠮𘠠𜐳𡁜𫡆𞀲𠱜𫡅𠐵𝁜𫠶𞑂𝰢𧐬𥀽𜀩𛁯𫡫𩑹𭑰👮🐾𚁑👳𦱶👔𚱛𛐱𛀵𛀱𛀭𝑝𦰳𙡮𛡷𪁩𨱨𧑝𚐾𘠰𘠿𬱛𬱛𥁝👑𛁔👶𧐽𘠠𘠺𜀬𩀽𩁯𨱵𫑥𫡴𛡢𫱤𮐬𩀮𪑮𫡥𬡈𥁍𣀽𘠼𬁲𩐾𘠫𬰮𪡯𪑮𨁠𛁤𛡳𭁹𫁥𛡦𫱮𭁓𪑺𩐽𙰵𩑭𙰻`.replace(/u../g,'')))

Apr 2 2020 9:23 AM UTC

}// 132/140

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15 puzzle #game #interactive

u/Kirjava

control with IJKL
u/katkip

Works on light theme

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New_Core

function u(t) {

c.style.filter=`blur(17px)contrast(2e3%)`
for(c.width|=i=11;i--;)x.fillRect(960+600*S(t+i),440+400*C(t+i/.6),200,200)

Feb 12 2020 4:46 PM UTC

}// 117/140

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Aha.. so thats how the metabals was done ;)

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u/New_Core

*metaballs
u/New_Core

probably better use arc.. didnt check fullscreen before posting....
u/New_Core

about 60 px blur was ok for fullscreen here
u/KilledByAPixel

nice technique!
u/corruptio

you can just do c.filter right?
u/corruptio

oh nope, nevermind
u/joeytwiddle

#metaballs good job!
u/sigveseb

Contrast filter, that's clever!

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corruptio

function u(t) {

t?x.fillRect(j%50*36,(j/50|0)*36,(v="򐉡󰘣󠱂򐐢󘑂򈑂󘑢򀑢󈒂񸒂󈒂񸒂󈒂񰒃󈒂񰑣󐒂񰑣󐓣𡱃󠑢񉁄󨙣󰘣󨩣󠚣󐛣󈗇𡊡𙆄𙀡򀒢𠰢𨑦𘑂𘑁񠰣𹂁𱂡򑐤𨗁𨑁񨑤𡈃𠳋󱸡󩆥􁁁𱏊򀖅򘠁".charCodeAt(i/2)>>i++%2*5&31)*36,i%2*36,j+=v):i=j=0

Jan 28 2020 3:01 AM UTC

}// 140/140

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50 x 28 Totoro #PixelArt

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u/corruptio

Uses run-length encoding to get more pixels.
u/Xen

very nice!!
u/corruptio

hmm, can save 4 chars in decoder to make it a 50x30 image
u/corruptio

t?x.fillRect(j%50*32,j/50<<5,(v="𝀳𯁱𦠢𤀡𦐢𣰢𦐣𣠣𥰤𣐤𥰤𣐤𥰤𣐤𥰤𫀤𥰤𫀣𦀤𫀣𮀣񈱢𘡚𰲇𘡻𜱼𤑻𜱺𝑸𝱗𰒎𘢕𰒌𘐡𣡥𠠡񀰣𠐢𘑢𪢁𙒄𙂥𴀡𘰮𘰢𲲃𨡰񨣦🂑𾲍🢂񡀾𻡌𜓬🰀".charCodeAt(i/2)>>i%2*5&31)*32,i++%2*32,j+=v):i=j=0
u/katkip

Awesome!
u/aleamb

fucking amazing!
u/tomxor

Do Ponyo! :)
u/KilledByAPixel

☂

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KilledByAPixel

function u(t) {

eval(unescape(escape`𭱩𭁨𚁸𚑦𫱲𚁩👴🰱𞡘👙🐲𩐳𛁺👧𩑴𢑭𨑧𩑄𨑴𨐨𦀬𦐫𞐬𜐬𜐩𛡤𨑴𨑛𜡝𞱩𛐭𞱢𩑧𪑮𤁡𭁨𚁦𪑬𫀨𩑬𫁩𬁳𩐨𭀿𦀺𪐬𭀿𦐫🐹𞠲𜀰𚡓𚁩𛰲𞐹𚐭𝀰𜀬𬐽𮠿𜰺𚁙🐰𛁘🐱𩐳𚱓𚁴𚐪𞐰𜁼𜀬𞐹𚐬𭀿𬐺𜑥𜰬𜀬𜀬𝰩𚐩𚑦𪑬𫁓𭁹𫁥👴𙠦𮠿𙰣𡡆𡠧𞠧𘰰𜀳𙰻`.replace(/u../g,'')))

Jan 22 2020 11:34 PM UTC

}// 140/140

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Bombs Away! 💣

u/tomxor

hah nice, oldskool colision detection :)
u/katkip

Reminds me of pocket tanks
u/tomxor

wait... this is almost literally your name :D

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rodrigo.siqueira

remix of d/17258 by u/pavel

function u(t) {

for(i=c.width|=p=(((K=t<5)?(t/8)**4:1)+t/5e4);i--;x.arc(960,540,1e3/z,b=(i*S(i*p))/20,b))z=1+(i>>12)+C(i*p);x.fill()

Jan 18 2020 11:46 PM UTC

}// 116/140

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From order (in the beginning there was void) to chaos (dynamic interactions).

u/katkip

haha nice!!!
u/Odog8

how dis work!??
u/joeytwiddle

It's a lot of overlapping triangles. To see: 5e4),i=99;i--
u/joeytwiddle

(sort of "triangles") Similar effects: d/915 and d/11742

dwitter.net | corruptio (2263)