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)*24.;
p.z-=4.;
for(j=0.;j++<32.;)
p=abs(abs(1.-p-.5))*rotate3D(t*.5,p-5.),
d=max(length(p.zx),length(p.zy))/d,
e-=d;
}o+=vec4(exp(1.-p*p),1)*3./i;