draft: refactor spawn

[MahooX]

Summary

• Replace the legacy scene-construction paths with DexSim Spawn.
• Keep the existing EmbodiChain add_* APIs and stable object facades through a declaration → prepare → bind lifecycle.
• Unify Default/PhysX and Newton preparation through sim.prepare(), including rigid, articulation, robot, soft-body, cloth, and rigid-object-group integration.
• Preserve native DexSim handling for lights and CameraGroup-based sensors, and update simulation tutorials for the new lifecycle.
• Keep singleton USD asset loading compatible through Spawn descriptors.

Validation

• Rebuilt and installed the matching DexSim package.
• Validated focused simulation tutorials and multi-environment flows on both Default/PhysX and Newton backends.
• Ran targeted syntax, formatting, and integration checks.

Type of change

• Enhancement

Dependency

Requires the matching DexSim Spawn implementation.

[greptile-apps]

Greptile Summary

The PR refactors simulation assets around a declaration, Spawn commit, runtime preparation, and facade-binding lifecycle.

• Introduces Spawn-backed rigid-body and articulation adapters.
• Moves environment robot and sensor setup around a centralized prepare boundary.
• Updates physics backends, spawn descriptors, tutorials, and lifecycle tests.

Confidence Score: 2/5

The PR does not appear safe to merge because Spawn attribute operations and articulation overrides remain broken, and failed facade binding cannot be retried.

Spawn rigid-body attribute methods still raise for supported facade operations, articulation finalization still omits configured non-mass physics attributes, and prepare() records a committed result before binding succeeds so a retry can skip the failed callbacks.

Files Needing Attention: embodichain/lab/sim/objects/backends/spawn.py, embodichain/lab/sim/objects/articulation.py, embodichain/lab/sim/sim_manager.py

Important Files Changed

Filename	Overview
embodichain/lab/sim/sim_manager.py	Centralizes declaration materialization and facade binding in SimulationManager.prepare().
embodichain/lab/sim/objects/backends/spawn.py	Adds tensor-layout adapters for Spawn rigid-body and articulation batches.
embodichain/lab/sim/objects/articulation.py	Adds declared and Spawn-bound articulation lifecycle support with post-bind configuration.
embodichain/lab/gym/envs/base_env.py	Splits scene declaration from post-prepare robot and sensor configuration.
embodichain/lab/sim/spawn/scene.py	Coordinates Spawn declarations, commits, and facade bind callbacks.

_{Reviews (6): Last reviewed commit: "prepare envs" | Re-trigger Greptile}

[greptile-apps]

Ready view exposes unsupported attributes

When a caller invokes set_friction or get_friction on a Spawn-bound rigid object, the ready body view dispatches to methods that unconditionally raise NotImplementedError, causing existing rigid-object attribute operations to fail. The finalized Newton attribute path also invokes the unsupported friction, restitution, and contact-offset setters.

Prompt To Fix With AI

This is a comment left during a code review.
Path: embodichain/lab/sim/objects/backends/spawn.py
Line: 280-288

Comment:
**Ready view exposes unsupported attributes**

When a caller invokes `set_friction` or `get_friction` on a Spawn-bound rigid object, the ready body view dispatches to methods that unconditionally raise `NotImplementedError`, causing existing rigid-object attribute operations to fail. The finalized Newton attribute path also invokes the unsupported friction, restitution, and contact-offset setters.

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For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.