Wetmachine Blog: Software

Discovery Part 2: How

 “The Universe is made of stories, not of atoms.” -Muriel Rukeyser

Last time, I discussed why we offer suggested locations to teleport to, and the 5 W’s of the user interaction for suggestions. This time I’ll discuss how we do that, with some level of technical specificity.

Nouns and Stories

Each suggestion is a compact “story” of the form: User => Action => Object. Facebook calls these “User Stories” (perhaps after product management language), and linguists refer to “SVO” sentences. For example, Howard => snapshot => Playa, which we display as “Howard took a snapshot in Playa”. In this case Playa is a Place in-world. The Story also records the specific position/orientation where the picture was taken, and the picture itself. Each story has a unique page generated from this information, giving the picture, description, a link to the location in world, and the usual buttons to share it on external social media. Because of the metadata on the page, the story will be displayed in external media with the picture and text, and clicking on the story within an external feed will bring them to this page.


The User is, of course, the creator of the story. The user has a page, too, which shows some of their user stories, and any picture and description they have chosen to share publicly. If allowed, there’s a link to go directly to that user, wherever they are.


For our current snapshot and concurrency user stories, the Object is the public Place by which the user entered. More generally, it could be any User, Place, or (e.g., marketplace) Thing. These also get their own pages.


The “feed” is then simply an in-world list of such Stories.


Analogously to any computer on a network and registering with ICANN, a High Fidelity user may create places at an IP address or even a free temporary place name, or they can register a non-temporary name. Places are shown as suggestions to a user only when they are explicitly named places, with no entry restrictions, matching the user’s protocol version. (When we eventually have individual user feeds, we could consider a place to be shareable to a particular user if that logged in user can enter, rather than only those with no restrictions.)

Snapshots are shown only when explicitly shared by a logged-in user, in a shareable place.



At metaverse scale, there could be trillions of people, places, things, and stories about them. That’s tough to implement, and tough for users to make use of the firehose of info. But now there isn’t that many, and we don’t want to fracture our initial pioneer community into isolated feeds-of-one. So we are designing for scale, but building iteratively, initially using our existing database services and infrastructure. Let’s look first at the design for scale:

First, all the atoms of this universe – people, places, things, and stories – are each small bags of properties that are always looked up by a unique internal identifier. (The system needs to know that identifier, but users don’t.) We will be able to store them as “JSON documents” in a “big file system” or Distributed Hash Table. This means they can be individually read or written quickly and without “locking” other documents, even when there are trillions of such small “documents” spread over many machines (in a data center or even distributed on participating user machines). We don’t traverse or search through these documents. Instead, every reason we have for looking one up is covered by something else that directly has that document’s identifier.

(There are a few small exceptions to the idea that we don’t have to lock any document other than the one being looked up. For example, if we want to record that one user is “following” another, that has to be done quite carefully to ensure that a chain of people can all decide to follow the next at the same time.)

There are also lists of document identifiers that can be very long.  For example, a global feed of all Stories would have to find each Story one or more at a time, in some order. (Think of an “infinitely scrollable” list of Stories.) One efficient way to do that is to have the requesting client grab a more manageable “page” of perhaps 100 identifiers, and then look up the document on however many of those fit on the current display. As the user scrolls, more are looked up. When the user exhausts that set of identifiers, the next set is fetched. Thus such “long paged lists” can be implemented as a JSON document that contains an ordered array of a number of other document identifiers, plus the identifier for the next “page”. Again, each fetch just requires one more document retrieval, looked up directly by identifier. The global feed object is just a document that points to the identifier of the “page” that is currently first.  Individual feeds, pre-filtered interest lists, and other features can be implemented as similar long paged lists.

However, at current scale, we don’t need any of that yet. For the support of other aspects of High Fidelity, we currently have a conventional single-machine Rails Web server, connected to a conventional Postgres relational database. The Users, Places, and Stories are each represented as a data table, indexed by identifier.  The feed is a sorted query of Stories.

We expect to be able to go for quite some time with this setup, using conventional scaling techniques of bigger machines, distributed databases, and so forth.  For example, we could go to individual feeds as soon as there are enough users for a global feed to be overwhelming, and enough of your online friends to have High Fidelity such that a personal feed is interesting, This can be done within the current architecture, and would allow a larger volume of Stories to be simultaneous added, retrieved, scored, and sorted quickly.  Note, though, that we would really like all users to be offered suggestions — even when they choose to remain anonymous by not logging in, or don’t yet have enough experience to choose who or what to follow. Thus a global feed will still have to work.


We don’t simply list each Story with the most recent ones first. If there’s a lot of activity someplace, we want to clearly show that up front without a lot of scrolling, or a lot of reading of place or user names. For example, a cluster of snapshots in the feed can often make it quite clear what kind of activity is happening, but we want the ordering mechanism to work across mixes of Stories that haven’t even been conceived of yet.

Our ordering doesn’t have to be perfect – there is no “Right Answer”. Our only duty here is to be interesting. We keep the list current by giving each Story a score, which decays over time. The feed shows Stories with the highest scores first. Because the scores decay over time, the feed will generally have newer items first, unless the story score started off quite high, or something bumped the score higher since creation. For example, if someone shares a Story in Facebook, we could bump up the score of the Story — although we don’t do that yet.

Although we don’t display ordered lists of Users or Places, we do keep scores for them. These scores are used in computing the scores of Stories.  For example, a snapshot has a higher initial score if it is taken in a high scoring Place, or by a high scoring User. This gives stories an effect like Google’s page ranking, in which pages with lots of links to them are listed before more obscure pages.

To keep it simple, each item only gets one score. While you and I might eventually have distinct feeds that list different sets of items, an item that appears in your list and my list still just has one score rather than a score-for-you and different score-for-me. (Again, we want this to work for billions of users on trillions of stories.)

To compute a time-decayed score, we store a score number and the timestamp at which it was last updated.  When we read an individual score (e.g., from a Place or User in order to determine the initial score of a snapshot taken in that Place by that User), we update the score and timestamp.  This fits our scaling goals because only a small finite number of scores are updated at a time. For example, when the score of a Place changes, we do not go back and update the scores of all the thousands or millions of Stories associated with that Place. The tricky part is in sorting the Stories by score, because sorting is very expensive on big sets of items. Eventually, when we maintain our “long paged lists” as described above, we will re-sort only the top few pages when a new Story is created. (It doesn’t really matter if a Story appears on several pages, and we can have the client filter out the small numbers of duplicates as a user scrolls to new pages of stories.) For now, though, in our Rails implementation, a new snapshot causes us to update the time-decayed score for each snapshot in order, starting from what was highest scoring. Once a story’s score falls below a certain threshold, we stop updating.  Therefore, we’re only ever updating the scores of a few days worth of activity.

Here are our actual scoring rules at the time I write this. There’s every chance that the rules will be different by the time you read this, and like most crowd-curation sites on the Web, we don’t particularly plan to update the details publicly. But I do want to present this as a specific example of the kinds of things that affect the ordering.

  • We only show Stories in a score-ordered list. (The Feed.) However, we do score Users and Places, because their scores are used for snapshots. We do this based on the opt-outable “activity” reporting:
    • Moving in the last 10 seconds bumps the User’s score by 0.02.
    • Entering a place bumps the Place’s score by 0.2.
  • Snapshot Stories have an initial score that is the decayed average of the User and Place – but a minimum of 1.
  • Concurrency Stories get reset whenever anyone enters or leaves, to a value of nUsersRemaining/2 + 1.
  • All scores have a half-life of 3 days on the part of the score up to 2, and 2 hours for the portion over 2. Thus a flurry of activity might spike a user or place score for a few hours, and then settle into the “normal high” of 2.  This “anti-windup” behavior allows things to settle into normal pretty quickly, while still recognizing flash mob activity.


For example, under these rules, one needs to move for about 3:20 minutes / day to keep your score nominally high (2.0).  More activity will help the snapshots you create during the activity, but only for a while, and snapshots the next day will only have an nominally high effect.

As another example of current rules, an event with 25 people will bump a place score by 5:

  • If it started at 2, it will back down to 4.5 in two hours, 2.5 in six hours, and back to 2 in 10 hours.
  • If it started at 0, it we be at 3.5 in two hours, and then roughly as above.


We currently search the filter on the client, filtering from the 100 highest scoring results that we receive from the server. Each typed word appears exactly (except for case) within a word of the description or other metadata (such as the word ‘concurrency’ for a concurrency story). There is no autocorrect nor autocomplete, nor pluralization nor stemming. So, typing “stacks concurrency” will show only the concurrency story for the place named stacks. “howard.stearns snapshot” will show only snapshots taken by me.

When the volume of data gets large enough, I expect we’ll add server-side searching, with tags.


We feel that by using the “wisdom of crowds” to score and order suggestions of what to do, we can:

  • Make it easy to find things you are interested in
  • Make it easy to share things you like
  • Allow you to affirm others’ activities and have yours affirmed
  • Connect people quickly
  • Create atomic assets that can be shared on various mediums

In doing so, we hope to create a better experience by bringing users to the great people and content that are already there, and encourage more great content development.

Also posted in Inventing the Future | Comments closed

Discovery Part 1: The Issue

“What is there to do here?”


High Fidelity is a VR platform.

It’s pretty clear how to market a video game. It’s a little bit harder to connect users to a new VR chat room, conferencing app, or Learning Management System. We’re not making any of these, but rather a platform on which such apps can be made by third party individuals and companies. Once someone has our browser-like “Interface” software, people can connect to any app or experience on our platform — if they know where to go.

The tech press is full of stories about The Chicken and Egg problem: adoption requires interesting content, but content development follows adoption. Verticals such as gaming make that problem a little more focused, but games still require massive up-front investment in technology, content, and marketing. We are instead betting on user-generated content in both the early market and, as with the Internet in general, we expect user-generated content to be the big story in mainstream adoption as well. This makes it that much more important to hook users up with interesting people, places, and things in-world. The early Web used human-curated directories for news, financial info, games, and so forth, but we’re not quite sure what categories are going to have the most interesting initial experiences. And neither do our users!

We want an easy way for users to find interesting people, places, and things to explore, which doesn’t require High Fidelity Inc. to pick and decide what’s hot. We also want an easy way for creators to let others know about their content, without having to go through us nor a third party to market it.

Crowd Curation

One powerful model that has emerged for recognizing interest in user-generated content is crowd curation: a strong signal is produced by real user activity, and used to drive suggestions.

The signal can be explicit endorsement (likes, pins, tweets, and links) or implicit actions (achievements, or funnel actions such as visiting or building). The signals are weighted in favor of the users you value most: friends, strangers with lots of “karma”, or sites with lots of links to them.

There are various ways in which this information is then fed back to users. Facebook and Twitter provide a feed of interesting activity. Google offers suggestions as you type, and more suggestions after you press return. Amazon tells you at checkout that people who bought X also bought Y. However, the underlying crowd curation concept is roughly the same, and it has accelerated early growth (Twitter, Zynga), and ultimately provided enormous value to large communities and their users (Google, Facebook, eBay).

Of course, these systems don’t crawl High Fidelity virtual worlds, so we need to make our own crowd curation system, or find a way to expose aspects of our virtual world to the Web, or both. But more importantly, what do we want to share?

For Real

So, what should we suggest to our users? Ultimately, we want to suggest anything that will give a great experience: people to meet or catch up with, places to experience, and things from the marketplace to use wherever you are. But in these early days, your friends are not likely to have gear or to be online at any given moment. Places are under construction and without reputation. The marketplace is just forming.

Initially then, we’re starting with just two kinds of suggestions:


  1. Taking an in-world snapshot is something that any user can do from any place, and it puts participants onto the road to being content creators. The picture can be taken with the click of a button and requires no typing, which can be hard to do in an HMD. We automatically add the artist username and the place name as description. It often gives a pretty good idea of what’s happening, and we’ve arranged for clicking on the picture to transport you to the very place it was taken, facing the same way, so that you can experience it, too. Finally, it creates a nice visual artifact that you can take home and share outside of High Fidelity.



  1. Even without necessarily knowing another High Fidelity user, it’s definitely more fun to go to places where people are. Even though we’re just in beta, there are always a few places that have people gathered, but they’re not always the same places. It’s hard for a person to know where to look. So we’re making suggestions out of public places, ordered by the number of people currently in them. No need for anyone to do or make anything on this one, as we pick up concurrency numbers automatically from those domains that share this info. (Anyone who makes a domain can control access to it.)



These suggestions appear when you press the “Go To” button, which also brings up an address bar where you can directly enter a known person or place, or search for suggestions (just like a Web browser’s address bar). I can imagine someday offering information about related content in various situations, or a real time messaging and ticker widget for those who want to keep tabs on the latest happenings, but primarily we just want to allow people to “pull” suggestions when they are specifically looking for something to do.

In short, when a person presses the “Go To” button, they get a scrollable list of suggestions that give a visual sense of what has been happening recently, which offers people the chance to visit.


Suggestions are available to both anonymous and logged in users: we don’t want to require a login to use High Fidelity. However, we would like to offer personalized feeds in the future based on your (optional) login. We also don’t share anything that you have not explicitly shared, and such sharing links to your (self-selected, non-real-world) username.

Sharing and searching are not restricted to our system. Every suggestion has a public Web page that can be shared on Facebook or Twitter, or (soon) searched on Google and other search engines. Clicking the picture or link on that page in a browser brings you to that same place in-world if you have Interface installed, just as if you had clicked on the suggestion within Interface. We feel this will make it easier for content creators to promote their places, snapshots, and eventually, marketplace items. We hope to create a “virtuous circle”, in which search and sharing brings people in through external networks that are much bigger than ours, introduces them to more content, and makes it easy for them to further make and share.

Does It Matter?

In the two weeks before we introduced an early form of this, a bit more than a third of our beta users were within 10 meters of another user in-world on any given day (excluding planned gatherings). Then we introduced a prototype of the concurrency suggestions (“N people are hanging out in some place name”), and over the next two weeks, nearly half each day’s users were near another a some point in their day. Since then, we’ve done other things to increase average concurrency, and we’re now near 100%.

I don’t have good historical data on snapshots, and the new data is quite volatile. Our private alpha “random image thread” averaged a healthy five entries a day for more than two years, including entries with no pictures and entries with multiple pictures. Now, on days when something interesting is happening, we get 20 or 30 explicitly shared pictures, with most days generating three to eight.

Next: How we do that

Also posted in Inventing the Future | Comments closed

High Fidelity Avatars: Interpretive Motion IK

meryWe’ve come up with something that I think is quite cool for conveying presence though our avatars. Interpretive Motion IK is a technique in which all kinds of inputs drive a small set of animated motions, and then the animation results and additional inputs both drive an Inverse Kinematic system. This gives us a rich set of built-in avatar behaviors, while also making use of an ever-evolving set of input devices to produce a dynamic and life-like result.

Why Aren’t Avatars More Like Us?

From static “head shots” in a text chat, to illustrations in a book and famous faces in a movie, avatars give us an intuitive sense of who is present and who is doing what. The story of an animated movie (or high end game “cut scene”) is largely shown through the fluid motion of anthropoids. A movie studio can hire an army of artists, or record body actors in motion capture suits. But a virtual world does not follow a set script in which all activity can be identified and animated before use. Avatar animation must instead be generated in real time, in response to a world of possible activities.

This challenge leads some systems to just show users as simplified images, or as just a head, a disembodied “mask and gloves”, or a mostly un-animated “tin can” robot. This may be appropriate for specialized situations, but in the general case of unlimited high fidelity virtual worlds,  the lack of whole-body humanoid animation fails to provide a fulfilling sense of personal immersion.

When it works well, the interpretation of motion is so strong that when another avatar turns to face your avatar, we describe it as “YOU can see ME”. In fact, the pixels on the screen have not turned, and cannot see. Think of the personality conveyed by the Pixar desk lamp hopping across the scene and looking at the camera, or the dancing skeletons of Disney’s early Silly Symphony. Unlike Disney and Pixar, High Fidelity aims to capture this rich whole-body movement as a realtime result of dynamic user input. Alas, today’s input devices give us only incomplete data. Interpretive Motion IK allows us to integrate these clumsy signals into a realistic sense of human personality and action.

Read More »

Also posted in Inventing the Future | Comments closed

What town contains Apple’s flagship Palo Alto store?

The answer is not Menlo Park. We’ve all made products that don’t work as well in the field as we’d like, but the Apple Maps folks really have to get out more.

Apple Maps showing labeling downtown Palo Alto as Downtown Menlo Park.

Apple Maps labeling downtown Palo Alto as Downtown Menlo Park.

And Safari froze when uploading this image to WordPress. Had to use Chrome…


Also posted in General, Inventing the Future, workflow | Comments closed

Meet you in the middle, John

Hah! I never figured Croquet and Lazlo to be in competition. See the comments here.

Also posted in Inventing the Future | 1 Comment (Comments closed)

a rant on copy protection

<rant on>

I could just slap Steve Jobs. He really had a good thing going with me, until today.

All the people I hang out with are pretty avidly anti-Microsoft, on technical, business, and moral grounds. I work at a University where I and everyone else use Macs. My wife was a Mac pioneer from way back, has a business that may soon be buying educational computers by the truckload, and is a perfect candidate for the “Switch’ ads. I like Pixar movies, and I’m tickled that ol’ Steve’s iTunes was able to show those RIAA guys what morons they’ve been.

Well, it that’s all changed.

Read More »

Also posted in Inventing the Future | Tagged , | 4 Comments (Comments closed)
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