PixelCompare method issue - autodesk-forge

Question

I have an issue with PixelCompare extension.
Here, i am loading it:
viewer1 = new Autodesk.Viewing.GuiViewer3D(document.getElementById('forgeViewer1'), { extensions: [ 'GoogleMapsLocator', 'Autodesk.AEC.Minimap3DExtension','Autodesk.AEC.LevelsExtension','Autodesk.DocumentBrowser','Autodesk.ToolbarExtension' ,'Autodesk.Viewing.PixelCompare'] });
Then im trying to use it :
viewer1.compareTwoModels(data[0],data[1]);
Data is an array containing the models.
I get a "viewer.compareTwoModels is not a function" error which means either there is a typo in the function name or it doesnt exist.
Without access to the extension repo, i cannot confirm this method indeed exists.
Im at loss as to what to do and will welcome any help.
EDIT:
This snippet loads the document in the viewer to display it.
Autodesk.Viewing.Document.load(`urn:${urns[index]}`, function(doc){
var viewables=doc.getRoot().getDefaultGeometry();
doc.downloadAecModelData();
viewer1.loadDocumentNode(doc, viewables, {
placementTransform: (new THREE.Matrix4()).setPosition({ x: increment, y: 0, z: 0 }),
keepCurrentModels: true,
globalOffset: { x: 0, y: 0, z: 0 }
}).then(i => {
if(urns.length > 1) {
$(viewer1.toolbar.container).find('#toolbarXLS').hide();
}
});
increment += parseInt(sessionStorage.getItem('padding1'));
});
Then, im using this to pixel compare it:
viewer1.loadModel('urn:dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLmwwLS10X0k5UkVhbnNWRXBuLXl5Zmc_dmVyc2lvbj0x', {}, (model1) => {
console.log('test load model :' + model1)
viewer1.loadModel('urn:dXJuOmFkc2sud2lwcHJvZDpmcy5maWxlOnZmLmxXX0dONUJNVDBxdDRuOGZmRWx4SkE_dmVyc2lvbj0x', {}, async (model2) => {
const pcExt = await viewer1.loadExtension('Autodesk.Viewing.PixelCompare');
pcExt.compareTwoModels(model1, model2);
console.log()
});
});
I get an instant "file extension unsupported" error, probably on the first argument the code does not reach console.log('test load model :' + model1).

Answer 1

The function compareTwoModels is part of the extension object, not the viewer - see PixelCompare extension
function launchViewer() {
var options = {
env: 'Local'
};
Autodesk.Viewing.Initializer(options, () => {
viewer = new Autodesk.Viewing.GuiViewer3D(
document.getElementById('forgeViewer'), {}
);
viewer.start();
// Load 2 sheets
viewer.loadModel('scissors1.pdf', {}, (model1) => {
viewer.loadModel('scissors2.pdf', {}, async (model2) => {
// Compare them
const pcExt = await viewer.loadExtension('Autodesk.Viewing.PixelCompare');
pcExt.compareTwoModels(model1, model2);
});
});
});
}