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Title	Fluid Simulation (Navier Stokes)
ID	5554947524870144
Created	4 years ago, 1614983982067
Updated	4 years ago, 1615143062186
Code	// https://www.dgp.toronto.edu/public_user/stam/reality/Research/pdf/GDC03.pdf // Drag mouse to interact var DeKhan = (function() { var plusPlusExp = new RegExp("__env__\\.KAInfiniteLoopCount\\+\\+;\\n", "g"); var ifClauseExp = new RegExp("\\n\\sif \$__env__\\.KAInfiniteLoopCount > 1000\$ {[\\s]+__env__\\.KAInfiniteLoopProtect\$'[^']'\$;[^}]+}", "g"); var wasFrameCount = frameCount; frameCount = function() { frameCount = wasFrameCount; return this; }; var globals = frameCount(); return function(f) { return Object.constructor('return (function(__env__) {return ' + f.toString().replace(plusPlusExp, "").replace(ifClauseExp, "") + ';});')()(globals); }; })(); draw = DeKhan(function() { // Simulation Steps: // (Init) Initial Density // 1. Add forces // 2. Diffuse // 3. Move fill(255); var // Editables N = 100, // resolution iter = 10, // diffuse iterations diff = 0, // rate of diffusion force = 2, // force of movement density = 60, // density of density visc = 0.02, // viscousity dt = 0.002, // delta time // Code iN = 400/N, Np1 = N+1, Np2 = N+2; visc /= N; diff /= N; density = N100dt; force = N100dt; var // u is horizontal component of vectors // v is vertical component of vectors u = [], v = [], pu = [], pv = [], // for interaction U = [], V = [], D = [], // d is density of each cell d = [], pd = []; // Helper functions function fill0(x,l) { // fills an array with zeroes x.length = Np2Np2; x.fill(0); } fill0(u); fill0(v); fill0(U); fill0(V); fill0(D); fill0(pu); fill0(pv); fill0(d); fill0(pd); this.loadPixels(); draw = function() { function set_bnd(b,x) { // set boundaries to negative values to contain // forces/densities within the canvas space // (b is 1) negate vertical walls (left and right) // (b is 2) negate horizontal walls (top and bottom) var i, l, b1 = b-1 ? 1 : -1, b2 = b-2 ? 1 : -1; for(i=1;i<=N;i++) { l = iNp2; x[l] = b1x[l+1]; x[i] = b2x[i+Np2]; x[l+Np1] = b1x[l+N]; x[i+Np1Np2] = b2x[i+NNp2]; } l = Np1Np2; x[0] = 0.5(x[1] +x[Np2]); x[l] = 0.5(x[1+l]+x[NNp2]); x[Np1] = 0.5(x[N] +x[Np1+Np2]); x[Np1+Np2] = 0.5(x[N+l]+x[l+Np1]); } function diffuse(b,x,x0,diff) { // diffuses densities/vectors var i, j, k, l, _l, a = dtdiffNN; for(k=0;k<iter;k++) { l = Np2+1; for(i=1;i<=N;i++,l++) { _l = l; for(j=1;j<=N;j++,_l+=Np2) { x[_l] = (x0[_l]+a( x[_l-1]+x[_l+1]+ x[_l-Np2]+x[_l+Np2]))/(1+4a); } } set_bnd(b,x); } } function advect(b,d,d0,u,v) { // move densities/vectors var i, j, l, _l, i0, j0, i1, j1, x, y, s0, t0, s1, t1, dt0 = dtN; l = Np2+1; for(i=1;i<=N;i++,l++) { _l = l; for(j=1;j<=N;j++,_l+=Np2) { // using the vector of the current cell, backtrack // to a cell that leads into the current cell and // get density/vector there x = i-dt0u[_l]; y = j-dt0v[_l]; x = x < 0.5 ? 0.5 : x > N+0.5 ? N+0.5 : x; y = y < 0.5 ? 0.5 : y > N+0.5 ? N+0.5 : y; i0 = x\|0; j0 = y\|0; i1 = i0+1; j1 = j0+1; s1 = x-i0; s0 = 1-s1; t1 = y-j0; t0 = 1-t1; // interpolation from cells nearby backtracked cell d[_l] = s0(t0d0[i0+j0Np2]+t1d0[i0+j1Np2])+ s1(t0d0[i1+j0Np2]+t1d0[i1+j1Np2]); } } set_bnd(b,d); } function project(u,v,p,div) { var i, j, k, h, l, _l; h = 1/N; l = Np2+1; for(i=1;i<=N;i++,l++) { _l = l; for(j=1;j<=N;j++,_l+=Np2) { div[_l] = -0.5h( u[_l+1]-u[_l-1]+ v[_l+Np2]-v[_l-Np2]); } } p.fill(0); set_bnd(0,div); set_bnd(0,p); for(k=0;k<iter;k++) { l = Np2+1; for(i=1;i<=N;i++,l++) { _l = l; for(j=1;j<=N;j++,_l+=Np2) { p[_l] = (div[_l]+ p[_l-1]+p[_l+1]+ p[_l-Np2]+p[_l+Np2])/4; } } set_bnd(0,p); } l = Np2+1; for(i=1;i<=N;i++,l++) { _l = l; for(j=1;j<=N;j++,_l+=Np2) { u[_l] -= 0.5(p[_l+1]-p[_l-1])/h; v[_l] -= 0.5(p[_l+Np2]-p[_l-Np2])/h; } } set_bnd(1,u); set_bnd(2,v); } function dens_step(x,x0,u,v,diff) { // diffuse and move densities diffuse(0,x0,x,diff); advect(0,x,x0,u,v); } function vel_step(u,v,u0,v0,visc) { // diffuse and move vectors diffuse(1,u0,u,visc); diffuse(2,v0,v,visc); project(u0,v0,u,v); advect(1,u,u0,u0,v0); advect(2,v,v0,u0,v0); project(u,v,u0,v0); } var x, y, l, _l, $l, t, mx, my, i, j, _min = this.Math.min, p = this.imageData.data, update = this.updatePixels; if(mouseIsPressed) { mx = this.mouseX; my = this.mouseY; x = mx/iN\|0; y = my/iN\|0; l = x+1+(y+1)Np2; d[l] += density; u[l] += (mx-this.pmouseX)force; v[l] += (my-this.pmouseY)force; } vel_step(u,v,pu,pv,visc,dt); dens_step(d,pd,u,v,diff,dt); $l = 1; for(i=1;i<=N;i++,$l++) { _l = $l; for(j=1;j<=N;j++,_l+=Np2) { t = _min(d[_l],255)\|0; l = (i-1)+(j-1)400 << 2; p[l] = t; p[l+1] = t; p[l+2] = t; } } update(); image(get(0,0,N,N),0,0,400,400); D.fill(0); U.fill(0); V.fill(0); text(this.__frameRate,20,20); }; });
Folds	5,17,81,87,167,221,223,282,284,291,293,306
Fork	false
Key	ag5zfmtoYW4tYWNhZGVteXIXCxIKU2NyYXRjaHBhZBiAgN2PoIbvCQw
Votes	219
Spin-Offs	5
Type	PJS
Width	400
Height	400
User Flagged	false
Origin Scratchpad	null
Hidden From Hotlist	false
Restricted Posting	false
By Child	false
Author Nick	Ethan Kim
Author Name	I2I0
Author ID	kaid_731859500478059353240442
Author Profile Access	PUBLIC

Archive Data

Added	10 months ago, 1739392987848
Updated	10 months ago, 1739392995103
Source Deleted	unknown