How do I use Motion to create a 3D Model Viewer Generator for Final Cut Pro that allows me to change 3D models?

Final Cut Pro does not accept USDZ or other 3D objects as media. Therefore, there's no reason for a 3D object Drop Zone.

However... If you're using Motion, you can apply several 3D models to the project and use a Replicator > Object Source as a Drop Zone. Replicators "honor" 3D properties and you can use the Angle Parameter as Orientation and the Scale Parameter to resize. You can also use the 3D object's Orientation and Unit Size in conjunction with the Replicator's controls. Once you add a 3D model to the Object Source, you can turn of its visibility (uncheck it) in the Layers List.

When using the Replicator, you'll want to set the Source to Line and the Start and End Points to 0,0; set Points to 1. (The 3D checkbox will automatically be set when replicating a 3D object.)

Add the 3D objects you want in your collection, then select the Replicator > Object Source (from the drop down menu at the right edge) and Add to Rig [Create New Popup]. In the Rig you can build a menu of objects. You can simply set the menu item, then drag and drop the model into the Object Source well from the Layers List.

I know this isn't really an ideal situation — it can be a real annoyance going back to Motion to add new models over time, but it's probably the best it can be for now. You could try providing feedback (from the Final Cut Pro menu) and suggesting the ability to import 3D models with similar Motion controls (Orientation and Unit Size controls)... and lighting control, if possible, would be an added bonus. (Ask nicely!)

Motion's lack of 3D object support is so outdated and tiring.

We had MotionVFX's m02 which was amazing. I used it all the time. Gave full 3D model support to Motion. But it's dead now. We've been promised an m03 to be compatible with new macOS and FCP versions, but we've been waiting over 3 years for it, and MVFX is not finished building it. I doubt we'll ever see it.

So what Fox_m mentions is exactly what you need to do. Really a shame Apple can't make Motion everything it should/could be.

FCP and Motion were never intended by Apple, nor marketed by Apple, to be replacements for anything. Motion and AE are quite different animals. Similar, but they each target a different user base. And, FCP and Motion run on the same render engine, which makes Motion the Took Kit for FCP. AND I will agree that Motion has been sorely neglected for many, many years now. So has Compressor (even worse). IMHO Apple would do well to purchase the m03 project from MotionVFX, get it working properly, integrate it into Motion natively. But, Apple will do as Apple will do. Grateful for what we do have, hopeful for what we don't, not making any expectations or demands.

My 2¢:

Motion is as advanced as it needs to be. The same "engine" is, after all, built right into Final Cut Pro. If you slight Motion, you're slighting Final Cut.

I've been using Motion for almost 18 years now and I am still finding new things and new methods of building what I want — and I'm still only using Motion 5.4.7. I've built 3D models from scratch inside Motion, built different variations of Keyers and other "color correction" tools to avoid dealing with the Final Cut Color board, I know how to build templates without the need of snapshots and recently figured out how to make shapes work in "negative" directions (normally, shapes disappear at width or height = 0). The list goes on (and on...) Motion has plenty of "untapped" capabilities. The very nice thing about Motion: everything created for Final Cut Pro still works in every version of FCP from the compatible version of Motion to the present. Templates built in Motion 5.0 still work today, even on the new processors.

As for the masks: all of those masks are available in Final Cut and if you create your templates as Effects, they are included in Final Cut for all Effect templates made in Motion. There are a few Effects supplied by Apple to Final Cut that you might notice do not include the Effects Masks features. These are the exceptions (and usually the Keyers and Mask effects).

So build what you need in Motion (as an Effect) and rely on Final Cut to provide all the masking power you need. Motion is not the video editor — Final Cut is.

As a user of Motion with the design of my own 3D animation short films (10-20 min), I cannot compare my experience with Foxes: it is only 10 times less that your respectable 18 years, ie. a mere one year or so. Nevertheless, as a sort of senior Motion newbie, I have a somehow different point of view concerning Motion and its support of 3D.

I constantly meet very high challenges when using Motion. Reading comments from users, it seems using Motion is fair from obvious and terribly frustrating for the beginners or to the occasional user. I experienced the same: The simplest designs are incredibly challenging and resume in one question: How to start?

I suppose that any computer design program offers such challenges in any domain. But speaking of my own experience, progressing with Motion is very slow. There are many times I wished I would switch to Blender. I may some day...

One of my greatest frustration with Motion’s 3D support is the fact that you have to think of your design in term of font and characters. Why so? I don’t know and I don’t want to know. That means, for every new design I start, I feel like I hold a hammer in my hand and I have to see all problems as nails. You know the story….

And I won’t speak of USDZ questionable support, that is known and documented.

Far from me to say that Motion is not advanced. It certainly is an extremely powerful tool, and I certainly believe Fox when he says you could do anything with it. I have myself designed some 3D models which I am proud of.

The trouble is, in every case: how to start? Most of videos on the web are outdated and unusable. The support from Apple help pages is not good enough to help starting off. 

I think Motion needs to be dusted off. I’d be very happy to use more of Motion capabilities. Apple please… (I asked nicely)

It’s interesting you should mention Blender… it is incredibly powerful but also very difficult to learn. It is a very different tool than Motion, in that it is actually made to model and render 3D objects. I have to say I tried it perhaps half a dozen times and was always kind of lost and gave up. In terms of learning curve it seems far more daunting than Motion. If only Motion could really integrate 3D objects with the rest of the tools and not like a separate thing (as with USDZ not interacting at all with layers, lights, etc), or Blender offering a more mac-like UI…

Sorry, I don't know if this is possible. There are probably more Motion power users monitoring the Motion Discussion group.