Tiny Raytracer from https://www.gabrielgambetta.com/tiny-raytracer.html

tinyraytracer.js

var m=600,w=[m,[0,-m,0],9,9,0,m,2,1,[0,0,3],9,0,0,m,3,1,[-2,1,4],0,9,0,9,4,1,[2,1,4],0,0,9,m,5],A=2,B=[8,[2,2,0]],D=Math,E=D.sqrt,F=D.max,G=0,H=document.getElementById("c"),I=H.getContext("2d"),J=I.getImageData(0,0,m,m),K=J.data;H.width=H.height=m;function O(p,g){return p[0]*g[0]+p[1]*g[1]+p[2]*g[2]}function P(p,g,z){return[p[0]-g[0]*z,p[1]-g[1]*z,p[2]-g[2]*z]}function Q(p,g,z,C){t=m;for(v=q=0;r=w[q++];q+=6)if(j=P(p,w[q],1),a=2*O(g,g),b=-2*O(j,g),d=E(b*b-2*a*(O(j,j)-r*r)))for(e=2;e--;d=-d)f=(b-d)/a,z<f&&f<C&&f<t&&(v=q,t=f);return v}function R(p,g,z,C){if(!(s=Q(p,g,z,m)))return 0;N=P(X=P(p,g,-t),w[s],1);n=O(N,N);i=A;for(l=0;u=B[l++];)k=O(N,L=P(B[l++],X,1)),i+=u*!Q(X,L,1/m,1)*(F(0,k/E(O(L,L)*n))+F(0,D.pow(O(M=P(L,N,2*k/n),g)/E(O(M,M)*O(g,g)),w[s+4])));p=w[s+c]*i*2.8;z=w[s+5]/9;return C--?R(X,P(g,N,2*O(N,g)/n),1/m,C)*z+p*(1-z):p}for(y=h=m/2;y-- >-h;)for(x=-h;x++<h;){for(c=0;4>++c;)K[G++]=R([0,1,0],[x/m,y/m,1],1,2);K[G++]=255}I.putImageData(J,0,0);