Baking is an import step to ensure your model retains it's detail while still being efficient enough for use within the All World platform. This will also ensure your USDZ file is accompanied by supplementary maps that enhance their realism in an AR space. Baking can be achieved in most 3D software packages, we will be covering the process in Substance Painter.
If you are unfamiliar with the step requires for model optimization, see the link here for adapting a digital sculpt in ZBrush [Reference ZBrush link]
Step 1: Loading the low poly model
Start a project in substance painter, and reference your reduced model under file. Your normal map format should also be changed from the default DirectX to OpenGL.
Step 2: Loading the high poly model
Under texture set settings, select "Bake Mesh Maps" from there a new window will appear. Select the icon opposite of "High definition meshes" to load your high resolution mesh. Adjust the settings to your liking and bake the desired maps.
The maps you've baked for your low poly model will now help retain all the detail of your high poly model. The supplementary maps you've created can also be furthered utilized for procedural texture creation.