When does an interactive world need reusable 3D assets?

I am part of the Mugen3D team at Sumeru AI. While writing about Atlas and Genie 3, I kept coming back to a product question: when is exploring a generated world enough, and when does an application need persistent, reusable 3D assets?

The distinction changes the implementation:

• Live world generation: the model produces what comes next as a user moves. This is compelling for exploration and simulation, but consistency, latency and inference cost become product constraints.

• Spatial generation and reconstruction: Atlas supports camera-controlled video, novel views and explicit 3D outputs. The relevant tradeoff depends on the output mode, so I would not treat it as only a video generator.

• Asset-first applications: our Mugen3D work starts with a reusable 3D representation, then adds rendering, animation, dialogue and interaction. This shifts work toward asset quality and runtime engineering, including memory, compression and integration.

There is no universal winner here. Single-image 3D still infers unseen surfaces; small text, reflective materials and complex geometry need review. Reusable assets do not remove rendering or animation costs, and this is not a benchmark comparison with Atlas or Genie 3.

For builders shipping interactive products: which requirement would make you choose persistent assets over live generation? Is it editing individual objects, export and engine integration, camera freedom, predictable runtime cost, or something else? I would be especially interested in concrete requirements from virtual showrooms, characters and simulation tools.

Official context: Atlas, Genie 3. Our product: Mugen3D.