Avatar portability version 2

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To enable user avatar travel from a grid service to another grid service, There are 3 problems to be considered:

  1. How to enable foreign user login - Authentication
  2. (If a foreign user can login)How to get a foreign user's belongings(including appearance, inventory)
    • This is discussed in this page
  3. Security

To achieve the 1st, client side changes are needed. SO, so far, I have only implemented the 2nd and the 3rd, and would like to explan my idea:

Basic Idea


  • User U1 resgitered at GridService G1
    • U1's inventory information is stored in InventoryServer I1
    • U1's assets are stored in AssetServer As1
    • U1's appearance information is served by AvatarService Av1
  • RegionServer R2 serves a sim at GridService G2
    • R2 fetches assets from Assetserver As2 by default.
    • R2 gets inventory information from InventoryServer I2 by default.

Avatar portability v2 1.PNG

avatar portability

AvatarPortability (or called "grid interoperability") is

  • U1 login to R2
    • U1's appearance at G1 can be seen from any other client which is connecting to R2.
    • U1 can CRUD(Create/Read/Update/Delete) its inventory/appearance through R2.

This means, (in the fig. 2) R2 should have the ability to connect not only its default UGAI server, but also external Inventory, Asset, Avatar service.

Avatar portability v2 2.PNG

Then "AvatarPortability" can be subdivided into 2 goals:

  1. How to let R2 know where are U1's storage services(Inventory,Asset,Avatar,...) ?
  2. How to enable R2 to interact with mutilple Inventory/Asset/Avatar services ?

Answer to the 1st How to - XRDS

more information can be found at:

A sample XRDS for U1 can be like:

 <?xml version="1.0" encoding="UTF-8"?>
 <xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
    <Service priority="0">
    <Service priority="0">
    <Service priority="0">
    <Service priority="0">
    <Service priority="0">

REASONS for proposing XRDS

  1. There are "UserAssetUrl" and "UserInventoryUrl" in "Users" table, they are cab be used to specify users' storage services, but it's lack of scalability, to think we may have "friend service", "currency service", ... we can not simply add a column for each service.
  2. XRDS is widly used, many languages has libs for discovering/parsing it. To use XRDS can increase the compatibility with existing(web) service
  3. XRDS is just a proposal, still, we have many other choices.

Answer to the 2nd How to - ForeignAssetHashTable

Why it is a problem ? The asset download process is described below:

  • RegionServer sends user/prims' Texture UUID to the client.
  • Client extract the UUIDs, and sends a "RequestImagePacket" to request the actual asset data.
  • RegionServer receives the AssetUUID and passes it to AssetServer to get the asset.

Avatar portability v2 3-1.PNG

  • Considering only 1 GridService, there is no problem, but if RegionServer knows more than 1 asset server, RegionServer has to determine which assetserver should be used.
  • Here ForeignAssetHashTable is used to solve this problem. (The detailed implementation is shown in following section.)
    1. when U1 login to R2, R2 register U1's owned asset UUIDs to "ForeignAssetHashTable".
    2. Client sends a RequestImagePacket
    3. R2 looks up into "ForeignAssetHashTable" to find the AssetServerUrl,(if not found, returns the default url)
    4. R2 use the returned AssetServerUrl to get asset data.

Avatar portability v2 3.PNG


  • All the implementation described here are already finished
    • The testing environment will be made public after solving the "security" issues.
  • Just for appearance portability, asseturl and inventoryurl are enough, so temporarily just use the 2 existing properties.
  • XRDS is not implemented

1 Implementation - ForeginAssetHashTable.Add

Avatar portability 4-1.PNG

2 Implementation - ForeginAssetHashTable.Get

Avatar portability 4-2.PNG

3 Implementation - ForeginAssetHashTable.Remove

Avatar portability 4-3.PNG

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