Mini Chladni

m n

<body onload='L=300;(oninput=e=>{a.width^=0;with(Math)for(x=L;x--;)for(y=L;
y--;)p=PI*x/L,P=PI*y/L,abs(cos(n[v="value"]*p)*cos(m[v]*P)-cos(m[v]*p)*cos(
n[v]*P))>.05||a.getContext`2d`.fillRect(x,y,1,1)})()'>m <input id=m value=9
 type=number> n <input id=n value=5 type=number><p><canvas id=a height=300>