createInstancedMesh.js

var mesh = null;
var dummy = new THREE.Object3D();
var sectionWidth = 200;

function addInstancedMesh() {
  // An InstancedMesh of 4 cubes
  mesh = new THREE.InstancedMesh(new THREE.BoxBufferGeometry(50,50,50), new THREE.MeshNormalMaterial(), 4);
  scene.add(mesh);
  setInstancedMeshPositions(mesh);
}

function setInstancedMeshPositions(mesh) {
  for ( var i = 0; i < mesh.count; i ++ ) {
    // we add 200 units of distance (the width of the section) between each.
    var xStaticPosition = -sectionWidth * (i - 1)
    dummy.position.set(xStaticPosition, 0, 0);
    dummy.updateMatrix();
    mesh.setMatrixAt( i, dummy.matrix );
  }
  mesh.instanceMatrix.needsUpdate = true;
}