[Fiware-miwi] SceneAPI features: original intent of the EPIC vs . current plans?

Philipp Slusallek Philipp.Slusallek at dfki.de
Wed Jan 15 08:04:28 CET 2014


Hi,

Lets discuss this today as well.

Best,

	Philipp

Am 15.01.2014 07:32, schrieb Toni Alatalo:
> a brief note about this, Jonne noted in the meet yesterday when this was
> discussed a little:
>
> we already can do selective sync — exactly due to existing IM things in
> Tundra. there’s no protocol for it but apps can do it with app level
> logic: for example a server side script that the client can command to
> configure the collection of entities of interest for that client. so the
> mechanisms for simulation servers to participate in scenes is there,
> just not tested that way yet (no demo / use case). thanks to Lasse’s
> recent (this & last week or so) refactoring in Tundra the kNet and
> WebSocket sync things are now integrated so that the same IM mechanisms
> work for WS connections too.
>
> however http interfacing can easily be useful too so might be a good
> idea to implement the original SceneAPI plan, for different cases than
> realtime sync.
>
> that does not help the browser-browser p2p case though that Philipp has
> also brought up.
>
> ~Toni
>
> On 03 Jan 2014, at 08:46, toni at playsign.net <mailto:toni at playsign.net>
> wrote:
>
>> Yes I agree that a selective form of how the sync / client works by
>> default might be good for e.g. AI or simulation nodes. But that is
>> basically just an optimization which does not change the architecture
>> fundamentally. That is, if there’s a use case for that kind of
>> SceneAPI (like the traffic data visualization I discussed with Uni
>> Oulu folks), we could just implement it right away on top of what we
>> have now.
>>
>> Support for selective Sync is required anyhow for scalability, for
>> large / with-much-constant-changes scenes and for large numbers of
>> users. We have a few such Interest Management strategies, and support
>> for IM in general, implemented in Tundra by CIE/Chiru a while back. I
>> think improving that is in Ludocraft’s fi-ware plans.
>>
>> In those usages it is typically the server which decides what updates
>> are of interest for a certain client, utilizing info that the client
>> has sent (in Chiru’s Tundra thing the client sends the active camera
>> view info for the server to use -- Second Life does the same I think).
>>
>> For these headless server-clients, we should support the client
>> subscribing explicitly to certain changes -- either changes to certain
>> objects, or perhaps changes of certain type to any object in the
>> scene. That should be easy to add when the support for IM in general
>> is well in place. Perhaps a good use case to be kept in mind when
>> working on IM. The Verse protocol, made many years ago for live sync
>> of changes between 3d authoring apps for realtime collaboration, works
>> like that: after connecting, clients subscribe to the kind of changes
>> they want to get from the scene (quite normal pub-sub style).
>>
>> For isolated queries and changes HTTP is fine, that would be
>> implemented by the current SceneAPI plan, and is simple. Just is not
>> suitable for more realtime simulation visualisations for which the
>> Websocket impl from Sync GE is better.
>>
>> WebRTC is certainly cool for direct browser-to-browser comms, works
>> well for us in the original browser-code-only n-player Pong
>> implementation (which was later ported to Tundra + WebTundra too). One
>> limitation there is that support had been in Chrome only, I don’t know
>> how that situation has developed. Lasse mentions WebRTC as a possible
>> alternative transport in the continuation plans for Sync (in the
>> FI-CORE proposal). I think it is totally feasible to allow
>> peer-to-peer sync with the generic scene replication messages over WebRTC.
>>
>> ~Toni
>>
>> Sent from Windows Mail
>>
>> *From:* Philipp Slusallek <mailto:Philipp.Slusallek at dfki.de>
>> *Sent:* ‎Thursday‎, ‎January‎ ‎2‎, ‎2014 ‎4‎:‎30‎ ‎PM
>> *To:* Toni Alatalo <mailto:toni at playsign.net>
>> *Cc:* FI-WARE, MiWi <mailto:fiware-miwi at lists.fi-ware.eu>
>>
>> Hi,
>>
>> Am 02.01.2014 15:08, schrieb Toni Alatalo:
>> > 1. use the library to connect to the scene server
>> > 2. use the WebTundra Scene API (in-memory JS) to examine the scene,
>> for example to do pathfinding — the whole scene data is replicated to
>> this AI client so the object positions etc. all are there
>> automatically (just the ec-data though, not assets, so it’s not that
>> heavy)
>> > 3. move a character, either by modifying the position directly in
>> the client (again using the scene api there) or by sending commands to
>> the server
>> >
>> > I think what I’m saying in your terms is that the scene model and
>> the client code in general in WebTundra is not pure synchronization
>> (which is just the network messaging part) but, well, a client with
>> scene replication.
>> >
>> > As mentioned before, with the Second Life protocol used with
>> Opensimulator there’s the LibOMV (Open Metaverse) which gives the same
>> for e.g. AI bots — a headless client which connects to a server, gets
>> the scene state automatically and provides it as an easy to use
>> in-memory API that e.g. AI code can use to query and modify the scene.
>> AFAIK people have been happy and productive with that.
>>
>> But this is exactly what I would like NOT to do. Why should the
>> simulation server have the full scene. This might be necessary in some
>> cases, but there are many where it is not.
>>
>> But I agree that the SceneAPI may be something that is more tailored
>> towards queries and isolated changes. One way to combine the two things
>> could be to use the Scene API to set up selected synchronization to the
>> simulation server for just the interesting aspects for cases where
>> continuous updates are necessary. The simulation server could then
>> decide to send back changes either through the sync channel (where
>> appropriate) or the Scene API.
>>
>> >> One obvious issue that Toni already talked about is the direction.
>> Contacting a browser instance is not possible without a server as we
>> know from Server-Based Rendering. But then we could design an
>> interface that allows for querying and changing a scene.
>> >
>> > Again the Sync GE does provide that, both in form of a WebSocket
>> protocol and a JS client lib made on top of that — you can query the
>> scene and modify it.
>> >
>> > But I think is a good idea for us (Lasse perhaps but I’m probably
>> too curious to skip it too :) to check that article to understand more
>> of what you are after.
>>
>> But WebSocket is again a server-only transport mechanism (and it is what
>> we are currently using as well). That may be fine for some cases but for
>> others a P2P connection through Web RTC might be required if all we have
>> are two Web applications.
>>
>> BTW, the paper used REST and this is quite limited connectionwise.
>>
>>
>> Best,
>>
>>  Philipp
>> > Cheers,
>> > ~Toni
>> >
>> >>
>> >> There is already is such a suggestion by Behr et, al
>> (http://dl.acm.org/citation.cfm?id=1836057&CFID=394541370&CFTOKEN=82263824)
>> that may be a good lpace to start. It based on HTTP/REST, though,
>> which would not work for a connection towards the browser, so we
>> should use WebRTC instead.
>> >>
>> >>
>> >> Best,
>> >>
>> >>  Philipp
>> >>
>> >> Am 21.11.2013 22:24, schrieb Toni Alatalo:
>> >>> On 21 Nov 2013, at 10:54, Lasse Öörni <lasse.oorni at ludocraft.com
>> <mailto:lasse.oorni at ludocraft.com>> wrote:
>> >>>> If there is a good concrete plan to how it should be done instead
>> it's not
>> >>>> at all too late to change (as any implementation has not began),
>> and if
>> >>>> it's administratively OK, for example our architecture pictures now
>> >>>> include the REST scene API described.
>> >>>
>> >>> I talked today with a guy who is working on the vw / visualization
>> front in the university project with the traffic sensors in the city.
>> >>>
>> >>> We agreed preliminarily that could use their data and system as a
>> use case for this SceneAPI biz on the fi-ware side — if you and others
>> here find it’s a good idea.
>> >>>
>> >>> Their data currently updates once per hour, though, so http would
>> work :)
>> >>>
>> >>> But he had already proposed as a next step a visualisation where
>> traffic is simulated / visualized as actual individual cars. We could
>> have that simulation service as a user of the scene api / sync biz to
>> control the cars so we’d get streaming nature for the data and much
>> harder reqs for the usage (in the spirit of the EPIC).
>> >>>
>> >>> I still have to confirm with the prof whose leading that project
>> that this all would be ok. We could do it so that the actual
>> implementation of the visualization and even the integration comes
>> from the uni and fi-ware (Ludocraft) only provides the API. I can use
>> some of my university time for this as the integration of the city
>> model and the traffic data is good to get there.
>> >>>
>> >>> This is not a must and I don’t mean to overcomplicate thing but
>> just figured that a real use case would help to make the *concrete
>> plan* that you called for above.
>> >>>
>> >>> The experience with the quick and simple POI & 3DUI integration
>> (completed yesterday) was great, I’ll post about it tomorrow hopefully
>> (the POI guys checked the demo today on ok’d it as this first minimal
>> step). So I hope more integrations and usage of the GEs takes us well
>> forward.
>> >>>
>> >>>> Lasse Öörni
>> >>>
>> >>> Cheers,
>> >>> ~Toni
>> >>>
>> >>> _______________________________________________
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>> >>>
>> >>
>> >>
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