Q:

How to set independent material for specific dbId

I am setting up material for an element with a particular dbId with the following code.
getFragIdListFromGuid is a function I implemented to retrieve fragIdList from certain dbId. But I found this one actually changing all of the fragment material in the scene. Do they share the material together? 
const fragIdList = await getFragIdListFromDBId(this.dataComponents, this.instanceTree, dbId)
fragIdList.forEach((fragId) => {
  let material = fragList.getMaterial(fragId)
  if (material) {
    material.opacity = opacity
    material.transparent = true
    material.needsUpdate = true
  }
})

A:

There's a chance that the material is shared amongst different fragments. To work around clone the original material before processing and apply the clone:
  let material = fragList.getMaterial(fragId).clone();
  if (material) {
    material.opacity = opacity
    material.transparent = true
    material.needsUpdate = true
  }
        viewer.impl.matman().addMaterial ('myCustomMaterial', material, true);
        viewer.model.getFragmentList().setMaterial(fragId, material);
        viewer.impl.invalidate(true);

