float i,j,d=.1,e; vec3 p;
for(i=0.;i++<64.&&d>1e-4;){
p=vec3((FC.xy-.5*r)/r.y,1)*64.;
for(j=0.;j++<4.;)
p=abs(p)*rotate3D(t*.3,vec3(-1,4,2)),
p.zy*=rotate2D(t*.5),
d=max(tan(length(p.xz)),sin(length(p.zy)))/d,
d-=dot(p,p)/d;
e-=sqrt(d);
}o+=vec4(exp(p/d),1)*3./i;

