How to Retrieve Forge Viewer objectTree?

Question

My goal is to highlight a room by adding new geometry to the viewer based on lines I have created in revit like they do here Link

but i can not figure out how to access

Answer 1

Shiya Luo was correct the viewer had not yet finished loading the geometry

in my extentions Load function I added two event listeners and made sure they both fired before trying to access the instanceTree

 viewer.addEventListener(Autodesk.Viewing.GEOMETRY_LOADED_EVENT, function () {
    finishedGEOMETRY_LOADED_EVENT = true;
    if(finishedGEOMETRY_LOADED_EVENT && finishedOBJECT_TREE_CREATED_EVENT ){
        afterModelLoadEvents(viewer);
    }
 });
viewer.addEventListener(Autodesk.Viewing.OBJECT_TREE_CREATED_EVENT, function () {
    finishedOBJECT_TREE_CREATED_EVENT = true;
    if(finishedGEOMETRY_LOADED_EVENT && finishedOBJECT_TREE_CREATED_EVENT ){
        afterModelLoadEvents(viewer);           
    }
 });

Answer 2

As of version 2.9 this is still working. Here's my console:

Here's a couple of things you can try:

1. Is viewer undefined? Are you in the correct scope when grabbing the viewer?
2. The document have to be loaded before you can grab the instance tree. When the document is loaded, an event called Autodesk.Viewing.GEOMETRY_LOADED_EVENT will be fired, then you can start manipulating the instance tree.

Simply do this:

viewer.addEventListener(Autodesk.Viewing.GEOMETRY_LOADED_EVENT, function () {
var instanceTree = viewer.model.getData().instanceTree;
});

For more structured code, follow this guide to add an extension.

There's a more detailed blog post on which event to listen for. It's still using the old way to get instance tree, though.