What’s up everyone? Matt here with the Maya Learning Channel
and today I wanted to make a quick video on getting started with USD in Maya
– including how to export your Maya models as USD data…
…then setting up an initial stage and referencing that data
to begin the layout process.
Now, if you’re listening to this and wondering "what the heck is USD",
stop right now and check out my primer on USD for artists…
For the rest of you, let’s get started.
So here you’ll see I have a number of assets I created in Maya,
which I now want export for my layout artist to combine on a USD stage.
First, for each of these models, I need to make sure the individual objects
reflect the prims I want to create.
Remember, a prim can be as big or small as you want.
Mostly, it will depend on the scale of your scene
and the level of versatility the layout department will need.
Once you’re happy with these breakdowns, you can export each of them
by first selecting the object…
…Then going to File > Export Selection.
In here, I’ll change the file type to “USD Export”…
…then enter the name of our USD file, and export to an appropriate subfolder.
And that’s it. You can repeat this process for each of the base assets for your scene.
Now that all my assets have been exported to individual USD files,
we can start building a layout with them.
So, starting with an empty scene,
I’m going to go to Create > Universal Scene Description (USD)…
In here you’ll find two options.
“Stage from file” is great if you already have a complex USD scene ready to go
(like Pixar’s kitchen for example).
However, in our case we’ll want an empty stage that we can start building on,
so I’ll select “Stage with new layer”.
This creates a stage and, if I right-click and open the USD Layer Editor, a new layer.
A couple of things to note here.
First, notice how the default name here is “anonymousLayer1”.
An anonymous layer is a layer that you haven’t saved yet.
It exists only on your machine as a sort of nameless entity – hence being “anonymous”.
Only by clicking the Save button here and outputting it to a USD file
does it become a proper USD layer.
In this case, I’ll call it “living_room_LAYOUT”.
However, this layer will be for my entire layout team – not just myself –
so I’d prefer not to work right on it.
So I’ll click here and create a sub-layer under it.
This will be MY working layer, which I’ll save as “initial_layout”.
Just be sure to target it by clicking here on the left so all upcoming changes will be on it.
Second, don’t forget to turn on “Shapes” in the Outliner when working in USD.
Now we can start importing our USD assets.
To do that, first I’ll right-click the stage’s shape node and go down to “Add new prim.”
There are a few different options in here, but the one I’m interested in is Xform.
This is similar to a Maya transform node in that it’s a prim that defines transform values.
Next, I’ll right-click the Xform and go to “Add USD Reference”.
Then I’ll just navigate to my directory with all my USD files…
…and load my chair.
And now you can see I have my chair here, as native USD data,
ready to be placed using your usual Maya tools.
To finish up, I’ll just rename the Xform appropriately.
Notice also that the Xform icon now has this little arc in the bottom right.
This is because it now represents a “composition arc.”
In USD, an arc represents the operation (or operations) targeting a prim / layer
or both that get us to an end result.
For example, our chair xform is targeted by the reference to the actual chair.usd file.
Actually, to be really accurate, the “initial_layout” sublayer
(upon which our chair is referenced) is ALSO a composition arc targeting the xform.
which could easily be referenced by another prim.
In addition to references and sublayers, other operators include variants
(which you saw in my previous video), inherits, payloads, and specializes.
I’ll show you these in later videos.
For now, I can repeat this workflow to reference each of my other USD assets.
Once I have all my USD assets here, with my initial layout,
I can go back and save the layers again.
And that’s it! Now when the next artist comes in and wants to add their own opinons,
they can create their own sublayer…
…then target it…
…and make whatever changes they want, including rearranging furniture,
adding new assets, or even removing ones I originally put in.
But all their opinions will only exist on their layer.
If I mute it, you’ll see that the scene goes back to the way I originally designed it!
Now you know the basis of exporting and referencing USD data in Maya.
But there’s a lot more to working in layers that I’ll get to in my next video,
so make sure to subscribe to the Maya Learning Channel
to get notified of that!
And also be sure to keep an eye out for my colleague Yingying’s companion series
on USD in Bifrost. There she’ll go into even more depth on USD concepts,
using Bifrost as both a teaching and visualization tool!
See you next time!