Your question is rather unclear to me but consider the following:
var overall = new THREE.Object3D();
for (var i=0; i<10; i+=1) {
var tet = new THREE.Mesh(new THREE.TetrahedronGeometry(),
new THREE.MeshLambertMaterial({color:0x909090}));
tet.position.set(i-5,0,0);
overall.add(tet);
}
now the overall
object is composed of ten independent tetrahedrons.
Alternatively, you might want just one mesh, so:
var tetGeo = new THREE.TetrahedronGeometry();
var compGeo = new THREE.Geometry();
var mv = new THREE.Matrix4();
for (var i=0; i<10; i+=1) {
var nt = tetGeo.clone();
mv.makeTranslation(i-5,0,0);
nt.appplyMatrix(mv);
compGeo.merge(nt);
}
var overallMesh = new THREE.Mesh(compGeo,
new THREE.MeshLambertMaterial({color:0x909090}));