VR Redux

Wed 04 January 2017 by Jim Purbrick

Mike and I have been talking about how to easily build simple networked social applications with ReactVR for a while, so I spent some time hacking over the Christmas break to see if I could build a ReactVR version of the pairs game in Oculus Rooms. Pairs is simple and fun, but also interesting as it’s real time and has the potential to generate conflicting updates that need to be resolved.

Redux seemed like a promising starting point as it reifies events and allows flexible event processing in a similar way to MASSIVE-3. I used websockets as they are already supported by ReactVR along with wsrelay to network the clients.

With those pieces in place the simplest way to network the clients is to implement a middleware function to send every action generated in one client to all the others. In the case of actions which show a tile this is sufficient as the action is idempotent. If two players click on a square at the same time, the order that the actions are reduced in doesn’t matter: in either case the result is that the element is revealed. We can exploit the idempotency by optimistically processing the action locally before sending it to other clients to minimise network latency.

Scoring is trickier. While each client can tell when a pair has been revealed, only the first player to reveal the pair should score a point. As the actions to reveal tiles are potentially processed in different orders on each client that could lead to inconsistent scores even if only the first is processed. A simple way to avoid this inconsistency is to nominate one client to be the master and only have that client generate score actions. This can be implemented as another middleware to avoid generating actions inside a reducer.

The master client can also be made responsible for sending the current state of the simulation to new clients to support late joining.

With those parts done the app is usable and makes an interesting example of one possible way to network ReactVR applications. This was the first time I’d used React, ReactVR or Redux and I was very impressed by how easy to use and flexible they are. With the addition of some small pieces of middleware Redux can be used to implement a distributed simulation with flexible consistency mechanisms to trade off latency and consistency. The pairs example shows that even within a simple application applying different consistency mechanisms to different actions and parts of the application state is useful.

The next things to experiment with are using WebRTC to allow peer to peer communication between clients to further reduce latency, add a server to allow trusted and hidden state and allowing clients to subscribe to a subset of actions to allow heterogeneous clients and interest management.

If you’d like to play the ReactVR version of pairs or see the rest of the code, it’s available on github here.


Creating A Safe Environment For People In VR

Mon 31 October 2016 by Jim Purbrick

I was very happy that Oculus found time at OC3 to host a panel on creating a safe environment for people in VR. As social VR becomes more popular over the next few years it will quickly have to learn how to keep people safe together in shared environments. Some ...

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crestexplorer

Sun 21 August 2016 by Jim Purbrick

At the 3rd Party Dev State of the Union at EVE Fanfest 2016 earlier this year, CCP FoxFour drew my attention to a limitation of the current approach used by crestmatic to generate CREST documentation: it only discovers resources always reachable from the API root from the perspective of the ...

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Strange Tales From Other Worlds

Tue 10 May 2016 by Jim Purbrick

At the end of last year, Michael Brunton-Spall and Jon Topper asked me if I would like to give the opening keynote at Scale Summit as I had “lots of experience scaling weird things”, by which they meant Second Life and EVE Online. I immediately thought of The Corn Field ...

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Towards A Generic Media Type System

Sun 17 April 2016 by Jim Purbrick

The early days of RESTful hypermedia API design tends to involve lots of homogeneous collections. In the case of CREST vnd.ccp.eve.Api-v1 pointed to the logged in vnd.ccp.eve.ccp.Capsuleer-v1 which pointed to a vnd.eve.ccp.CharacterCollection-v1 of contacts which pointed to many vnd.ccp ...

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#recordstoreday

Fri 15 April 2016 by Jim Purbrick

StoryBirdAlbum

3 weeks ago I spent a few hours with photoshop working on the Story Bird logo that Linda made a while ago to make it suitable for print. 2 weeks ago I spent a few hours researching the best way to convert the 24 bit 48 Khz Story Bird mixes ...

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#bandcampday

Sat 26 March 2016 by Jim Purbrick

Black barn mixing desk

I love record shops. Whenever I had pocket money it would go on Metallica and Nirvana CDs bought from Our Price or black t-shirts to match. When I lived in Nottingham I bought Boards Of Canada CDs from the same Selectadisc that my Dad bought a rare Fairport Convention single ...

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crestmatic

Sun 03 January 2016 by Jim Purbrick

A year ago I gave a talk at EVE Vegas about building RESTful CREST applications. My #1 recommendation was to specify representations in requests, but that’s hard to do when there is little documentation on which representations are available and what they contain.

Fortunately CREST is self describing: send ...

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Free Tests For Everyone!

Thu 11 June 2015 by Jim Purbrick

Modern software development is sometimes colourfully described as being similar to firing tracer bullets at a target. Rather than spending time doing a lot of research, design and specification up front, the smallest, simplest version of the software is built and the feedback gathered from its use is used to ...

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Investing In Testing

Wed 10 June 2015 by Jim Purbrick

Droidcon London

Last year I was talking to an engineer at Droidcon London who was working on an Android app with 100% test coverage. I immediately asked whether he thought 100% test coverage was worthwhile: many software engineering teams strive to achieve 100% test coverage, but few succeed because it’s an ...

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buckd

Mon 18 August 2014 by Jim Purbrick

BuckGraffiti

One of the things I’ve been working on since joining Facebook is Buck, an open source Android & Java build tool which is significantly faster than many other Java build tools for a number of reasons.

As well as being fast, Buck gains a lot of power and flexibility by ...

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Organisational Structures

Thu 20 March 2014 by Jim Purbrick

There have been a number of blog posts recently about exciting new organisational structures. As Cory points out “Every early stage company thinks it has reinvented management”: a very dangerous belief when betting on a new organisational structure can be much riskier than betting on the wrong product.

It starts ...

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Beyond Time Dilation?

Wed 29 January 2014 by Jim Purbrick

The Battle of B-R5RB

EVE online is a remarkable game. On Monday over 2000 people spent over 20 hours destroying virtual spaceships worth 200,000 USD in real money in what was the likely the largest battle in a video game ever. That EVE is capaple of supporting such large engagements is an amazing ...

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Osprey Therian

Sun 15 December 2013 by Jim Purbrick

In mid-2004 I first started exploring Second Life. Version 1.4 had just been released and Philip Rosedale had said in the press release “My fantasy is to be Uma Thurman in Kill Bill, and now I can. I’d pay $10 for her yellow jumpsuit and sword moves and ...

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Parse By The Sea

Sat 19 October 2013 by Jim Purbrick

#parsebythesea

A few weeks ago Facebook London hosted the Parse By The Sea hackathon at the Brighton Dome as part of the Brighton Digital Festival. The idea was to take one of our internal hackathons on the road and invite members of the public to join us, turning a hackathon in ...

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Facebook Hackathons

Mon 16 September 2013 by Jim Purbrick

I’ve been a big fan of hackathons since one of the first Yahoo! Hack Days I attended at Alexandra Palace was struck by lightning. The lightning caused the fire alarms to go off which opened the roof to let the torrential rain pour on to hundreds of geeks and ...

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Brighton Digital Festival

Wed 04 September 2013 by Jim Purbrick

The Brighton Digital Festival starts this week and I’m very happy to be helping out with Facebook London‘s contributions: Parse By The Sea, a mobile app Hackathon featuring Parse on the 26th of September, and helping to Connect The Brighton Digital Festival by sponsoring Metranet to provide high ...

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Final Score

Thu 04 July 2013 by Jim Purbrick

Google Reader

Using Reader on my HTC Wizard on the loo was probably responsible for my biggest increase in clue ever.

Goodbye Reader, you’ll be missed.

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One Universe, Many Scales

Thu 10 January 2013 by Jim Purbrick

One epic meta-game design I first remember talking about a decade ago while working on Warhammer Online is the multi-scale online game: a system of interconnected games in which you choose to be a solo operative, work in a small group, or command epic forces or huge space fleets and ...

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Creatarr

Wed 09 January 2013 by Jim Purbrick

cc image by vdu, j4mie

One of the things I’ve been tinkering with since leaving Linden Lab is Creatarr: a creative, collaborative social game. Creatarr’s goal is to bring some of the magical collaborative creation found in Second Life to a wider audience and to push creativity in ...

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