// Create a new instance of the modifier and pass the number of divisions.
var subdivisionModifier = new THREE.SubdivisionModifier(3);
var tessellateModifier = new THREE.TessellateModifier(8);

// Apply the modifier to our cloned geometry.
for(var x=0; x<6; x++) {
    tessellateModifier.modify(polyGeometry);
}

subdivisionModifier.modify(polyGeometry);