Maybe this is more clear.
On page https://github.com/hofk/THREEf.js/tree/master/THREEf_90
geo.js
modifyCreateGeo.html
modifyCreateGeoOnlyIndexed.html
modifyGeo.html
See also
Addon. Produces almost infinite many time-varying geometries with functions
page 37
try it out
https://hofk.de/main/threejs/sandboxthreef/modifyCreateGeo.html
