Added possibility to load USD from command line

[michalpelka]

Firstly, thanks for this Hydra demo!

I've added nice feature to load USD from argc.

I've also needed to add X11 to my cmake to compile.

[raph080]

Hi @michalpelka,

Thank you very much for diving into this demo code.

Good to know about x11, is it required in order to run the tool on Linux?

I think the extra argument for the command is really convenient in case people wish to use the tool and focus on USD data.

On my hand, I created the tool to focus on Hydra data. USD is just like a plugin, a custom view that feeds Hydra from USD stage.

we could have other custom views feeding Hydra from various file formats (what about creating an adapter from json, or gltf, or ...).

For this reason I keep the core of the tool USD independent.

Thank you @michalpelka!

[michalpelka]

X11 was needed to link some tagers from OpenUsd install.

[michalpelka]

So feature should be more or less optional when view is available, right?

[raph080]

That could be a way of implementing it indeed !