Proposal to add support for managing simulation worlds #4

ayushgnv · 2025-04-01T21:36:06Z

Proposal for World Management Services for Simulation Interfaces Standard

These interfaces provide standardized world management across simulation_interfaces.

The proposed API introduces functionality to dynamically load and unload worlds, enabling automated testing across diverse simulation environments without restarting the simulator. This would allow for workflows where users can load a world file, spawn entities, and run SIL testing facilitating continuous operation on remote systems (sometimes in headless mode).

For Isaac Sim and O3DE (@adamdbrw), these services would likely be useful as these platforms support loading worlds dynamically.

Unlike Entities only one world should be loaded at a time. Attempting to load a world when a world already exists should result in automatically unloading the previously loaded world before loading the current one.

Change Summary:

New message: WorldResource
New services: LoadWorld, UnloadWorld, GetCurrentWorld, GetAvailableWorlds
Added corresponding feature flags (40-44) to SimulatorFeatures.msg
Added world_formats field to track supported world file formats

pijaro · 2025-04-08T07:57:16Z

I think it's a good idea.

However, I'm missing an additional simulator state. Setting up a new world will take time, and we should consider that. I suggest adding something like this to SimulationState.msg:

uint8 STATE_INITIALIZING = 4  # Simulation resources are being loaded; the simulation is not running and cannot be started, stopped, or paused.

adamdbrw · 2025-04-09T14:23:18Z

Good PR, I would love to follow up and propose changes soon, will submit as a PR targeting this one.

ayushgnv · 2025-04-11T02:50:42Z

I think it's a good idea.

However, I'm missing an additional simulator state. Setting up a new world will take time, and we should consider that. I suggest adding something like this to SimulationState.msg:
uint8 STATE_INITIALIZING = 4  # Simulation resources are being loaded; the simulation is not running and cannot be started, stopped, or paused.

@pijaro Thanks, great idea! Added STATE_INITIALIZING to SimulationState.msg

Signed-off-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

adamdbrw · 2025-04-17T14:07:26Z

ayushgnv#1 - there's the PR

Signed-off-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

suggested changes to simulation interface worlds

adamdbrw · 2025-04-24T08:52:52Z

@mjcarroll @peci1 @DLu could you take a look at this one?

peci1

I went through this and left a few comments.

srv/LoadWorld.srv

msg/SimulationState.msg

srv/GetAvailableWorlds.srv

srv/LoadWorld.srv

Co-authored-by: Martin Pecka <peci1@seznam.cz>

srv/LoadWorld.srv

Co-authored-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

…ulationState

mjcarroll · 2025-05-12T12:53:30Z

@peci1 any more feedback here or are we good?

DLu

Apologies for the late review.

The thing that confuses me is what actually goes in the URI. I imagined them as unique ids, but LoadWorld.srv specifies them as having a specific format, like SDF.

DLu · 2025-05-12T20:05:57Z

msg/SimulationState.msg

+uint8 STATE_NO_WORLD     = 4           # Simulation world is currently unloaded and a new world has not finished loading yet.
+                                       # The simulation is inactive and cannot be started, stopped, or paused.


I feel like NO_WORLD is a little too specific in this context and STATE_TRANSITIONAL would be better.

Suggested change

uint8 STATE_NO_WORLD = 4 # Simulation world is currently unloaded and a new world has not finished loading yet.

# The simulation is inactive and cannot be started, stopped, or paused.

uint8 STATE_NO_WORLD = 4 # Simulation world is currently unloaded, and/or a new world has not finished loading yet.

# The simulation is inactive and cannot be started, stopped, or paused.

I'm not 100% sure with my English here. Would TRANSITIONAL also semantically cover the instant where no world is loaded and no world is commanded to be loading?

DLu · 2025-05-12T20:11:24Z

msg/WorldResource.msg

+# URI which will be accepted by LoadWorld service, unique per world.
+string uri


So we already have the Spawnable.msg in this package that has a string uri, string description and a spawn_bounds. I think this would be cleaner if we eliminated the non-unique name from this message.

I think semantically any Spawnable object is spawned while simulation is running. Whereas a world would be something you load by stopping sim, opening a new world which resets the current simulation. We could look into renaming or updating the descriptions in Spawnable.msg if we would still like to reuse this message type for loading worlds.

@adamdbrw @peci1 @mjcarroll any thoughts on this?

I think what repeats here is uri and description, which could be abstracted into "Resource", but a world is essentially quite a different type of thing - something that is required for spawning anything (in it).

I think its fine to have Spawnable and WorldResource. My point was to highlight the difference that both have a uri and description, but only worlds have names.

I'm also okay with keeping this separate message. However, see further.

DLu · 2025-05-12T20:14:27Z

srv/LoadWorld.srv

+string uri
+
+# Simulation world passed as a string. This field is used if the uri field is empty.
+string resource_string


Would it make more sense to have two separate services.

Add World, which takes in a resource_string and makes it available for use

Load World, which only takes a uri

Would does "makes it available for use" entail for the simulator? Is there any pre-processing that needs to happen before loading a world in your case?

Does "adding" have a value from the perspective of external interface node / automation? I am of opinion that it is an implementation detail, some resources need to be downloaded and other will be available; I would expect the simulator to handle that.

Perhaps it would be useful to document that loading can take a bit and make things clearer through error codes, suggesting async service call etc, what do you think?

So from an abstract perspective, here's what I imagine.

As an external client, I call GetAvailableWorlds.srv and get a list of unique world uri.

worlds: [ - {uri: 'factory1'} - {uri: 'competition_2'} - {uri: 'moon} ]

I could then call LoadWorld.srv with uri: 'moon'. However, if instead I wanted to load in some other world that is not specified yet, I could call AddWorld.srv with the resource_string (which I assume would be SDF or similar), and then that new world be listed in the available worlds.

The core issue here is that I think it is semantically cleaner to run separate Add/Load calls than it is to have the single Load call with different behavior if the uri field is empty or not. Also, what happens when uri is nonempty and resource_string is nonempty?

It seems to me it could be beneficial to create a Resource message like this:

string uri string resource_string # only used if uri is empty

This could then be used in Spawnable, WorldResource and here.

The proposal with AddWorld/LoadWorld seems too complicated to me.

ayushgnv · 2025-05-13T05:50:42Z

Apologies for the late review.

The thing that confuses me is what actually goes in the URI. I imagined them as unique ids, but LoadWorld.srv specifies them as having a specific format, like SDF.

@DLu At least from an Isaac Sim perspective we would load USD files by accessing the filepaths in the URI field. Happy to update the LoadWorld.srv message type or description to be something more permissive.

DLu · 2025-05-13T16:24:59Z

Apologies for the late review.
The thing that confuses me is what actually goes in the URI. I imagined them as unique ids, but LoadWorld.srv specifies them as having a specific format, like SDF.

@DLu At least from an Isaac Sim perspective we would load USD files by accessing the filepaths in the URI field. Happy to update the LoadWorld.srv message type or description to be something more permissive.

Might just be me, but I could benefit from a description of how you envision these services being used, similar to the "call this one, then this one" example I gave above.

peci1 · 2025-05-14T20:50:29Z

msg/WorldResource.msg

+# URI which will be accepted by LoadWorld service, unique per world.
+string uri


I'm also okay with keeping this separate message. However, see further.

peci1 · 2025-05-14T20:56:15Z

srv/GetAvailableWorlds.srv

+
+# Optional field for additional sources (local or remote) to search, 
+# specified as standard URIs if possible.
+string[] sources


Suggested change

string[] sources

string[] additional_sources

Also, it's not clear to me what should I type in this field. Is it https://app.gazebosim.org/fuel/worlds or https://fuel.gazebosim.org/1.0 or something else?

Last, what to do if there are standard online source (like the Fuel database), but we'd like to allow these use-cases without the user needing to look up docs for some particular URI?

Search only locally available worlds, not connecting to the Internet

Search also the default online locations

As one possibility, I think the worlds could get a virtual tag LOCAL or ONLINE which would tell whether they are locally available or not. The implementations could then first check for this particular tag filter and skip the online search when it is not needed. But what if the implementation doesn't support world tags?

peci1 · 2025-05-14T21:01:39Z

msg/SimulationState.msg

+uint8 STATE_NO_WORLD     = 4           # Simulation world is currently unloaded and a new world has not finished loading yet.
+                                       # The simulation is inactive and cannot be started, stopped, or paused.


I'm not 100% sure with my English here. Would TRANSITIONAL also semantically cover the instant where no world is loaded and no world is commanded to be loading?

peci1 · 2025-05-14T21:05:58Z

srv/LoadWorld.srv

+string uri
+
+# Simulation world passed as a string. This field is used if the uri field is empty.
+string resource_string


It seems to me it could be beneficial to create a Resource message like this:

string uri string resource_string # only used if uri is empty

This could then be used in Spawnable, WorldResource and here.

The proposal with AddWorld/LoadWorld seems too complicated to me.

ayushgnv added 2 commits April 1, 2025 13:06

Added new interfaces for simulation worlds

317a324

Fix formatting

7fa4b97

ayushgnv changed the title ~~Proposal to add support for modifying simulation worlds~~ Proposal to add support for managing simulation worlds Apr 1, 2025

Updated descriptions

4a2b01a

Added STATE_INITIALIZING in SimulationState.msg

1d52661

suggested changes to simulation interface worlds

26c067e

Signed-off-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

adamdbrw and others added 2 commits April 22, 2025 10:44

Applied review remarks + added extra feature field

bc1330a

Signed-off-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

Merge pull request #1 from adamdbrw/simulation_world_changes

075362d

suggested changes to simulation interface worlds

adamdbrw approved these changes Apr 24, 2025

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peci1 suggested changes May 1, 2025

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ayushgnv and others added 3 commits May 2, 2025 00:38

Update srv/GetAvailableWorlds.srv

1d17053

Co-authored-by: Martin Pecka <peci1@seznam.cz>

Update srv/LoadWorld.srv

ebc825a

Co-authored-by: Martin Pecka <peci1@seznam.cz>

Removed urdf mention in LoadWorld service

ac35bad

adamdbrw reviewed May 5, 2025

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srv/LoadWorld.srv Show resolved Hide resolved

ayushgnv and others added 3 commits May 5, 2025 17:05

Update srv/LoadWorld.srv

a509fe1

Co-authored-by: Adam Dąbrowski <adam.dabrowski@robotec.ai>

Added WorldResource in LoadWorld and renamed to STATE_NO_WORLD in Sim…

fdf07e4

…ulationState

Fix formatting

bf5f7b6

ayushgnv requested a review from peci1 May 6, 2025 10:59

mjcarroll approved these changes May 12, 2025

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DLu reviewed May 12, 2025

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peci1 reviewed May 14, 2025

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		uint8 STATE_NO_WORLD = 4 # Simulation world is currently unloaded and a new world has not finished loading yet.
		# The simulation is inactive and cannot be started, stopped, or paused.

		# URI which will be accepted by LoadWorld service, unique per world.
		string uri

Proposal to add support for managing simulation worlds #4

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ayushgnv commented Apr 1, 2025

Proposal for World Management Services for Simulation Interfaces Standard

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pijaro commented Apr 8, 2025

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adamdbrw commented Apr 9, 2025

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ayushgnv May 13, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ayushgnv commented May 13, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ayushgnv May 13, 2025 •

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