The structure

As you will notice from the image above, we’ve gone with a multi-repository approach. This has a number of benefits for us internally, such as less duplication of files, as well as for those externally in that we can lock the public repository to specific external revisions to avoid pushing out code which might break compatibility.

Lib repository

Contains mainly third party source and binaries that we make use of in the platform.

Common repository

Contains the public source code for the VastPark libraries as well as VastPark developed specifications such as IMML, Metaforik and Continuum

Public repository

Externals common and lib repositories and sample projects developers can use to understand how the system works. It’s recommended that external developers work off the public trunk

Legacy code

Two quick points on some legacy issues to be aware of:

• There are some orphaned branches in public that we plan to keep around for a little bit longer as we migrate code out of there and into the new structure, please avoid working against these branches as they won’t be around for too much longer!
• There are two legacy folders, legacy-slimdx and legacy that exist in the common repository. These libraries will slowly be dropped in favour of newer code that replaces the functionality within. We plan to be much more sane with the number of projects in future

Getting the source

Using a subversion client, SVN checkout from:

http://vastpark.svn.cvsdude.com/public/trunk/

Be sure to enable externals or you will find only a fraction of the source code will be downloaded.

Happy coding! I’m interested to hear how simple it is to get up and running with the source code. Comments both positive and negative are welcomed on this.

Many months ago during May of 09, after meeting Ian Hughes at FCVW, I came across an interesting post on his blog discussing an implementation of the flocking algorithm in Unity.

I’d not heard of the term flocking or boids, so proceeded to get stuck into some research, which lead me to Conrad Parker’s page on Boids Pseudocode as well as many others who had implemented the algorithm, I figured it would be a fun little plugin to write for VastPark so gave it a try.

Implementing the algorithm

Thinking about what was required, I came up with the following as the plan for the plugin:

• Any IPositionalElement (Model, Primitive, Sound, Camera, Light, etc) would be supported
• Implement Rule 1 – “Boids try to fly towards the centre of mass of neighbouring boids”
• Implement Rule 2 – “Boids try to keep a small distance away from other objects (including other boids)”
• Implement Rule 3 – “Boids try to match velocity with near boids”
• For bonus points I’d implement “Tendency towards a particular place”, “Limiting the speed”, “Bounding the position”, “Perching” and “Scattering the flock”

In terms of the plugin this translates into these properties:

• SmallDistance
• MaxVelocity
• MinVelocity
• EnableBounds
• MaxBounds
• MinBounds
• EnablePerching
• MinPerchTime
• MaxPerchTime
• PerceivedCentre (get only)

The following callbacks:

• ElementPerched
• ElementLeftPerch

The following methods:

• SetPointOfInterest
• AddPlaceToAvoid
• AddPerch
• Scatter

The class diagrams look like this:

How does it work?

Put quite simply, the plugin works like this:

• AddElement(ImmlElement element) creates a boid instance for the positional element passed
• The plugin Update method (called once each update by the VastPark framework) proceeds to calculate the rules, one at a time for each boid to work out the new velocity and position for the element it represents
• Scatter requests made during runtime are dealt with during the next update

Downloads

Here is some sample IMML and the source code to the plugin, enjoy! Let me know if you decide to implement any of the other rules or do something cool with it

Sample IMML: flocking.imml
Source code to plugin: Plugin.Flocking.zip

Note: The source code will probably complain about some missing references. Install the Player from www.vastpark.com and link against the relevant binaries included with it.

If you haven’t already read the original article and are interested in how it works, be sure to have a read before continuing.

Define Element

The Define element is a declarative way of expressing a variable in IMML. It’s equivalent to doing element:set(‘variableName’, variableValue) but doesn’t require interpretation via the scripting engine which results in much better performance. It’s also a much nicer way to store global variables as they can be placed in more a easily identifiable location in the IMML rather than being buried within a script.

My Define in the sample looks similar to this (truncated for brevity):

<!--Use any Yahoo stock codes in the below define to control the stocks being generated and updated-->
 <Define Key="stocks" Value="IPL.AX,VIL.AX,FMG.AX,RIO.AX,BHP.AX,BOQ.AX" />

To change the ticker to show different stocks, replace any of the entries in the Value of the Define with the appropriate Yahoo ticker code for the relevant stock.

Tooltip Plugin

Note: To use the Tooltip plugin, you’ll need to be running either the most recent Player snapshot or version 0.98+ as it uses the Handle property that was added recently to the IRenderEngine interface.

The tooltip concept has been around for quite a while and is used by just about every modern desktop application. Ever wondered what that big red button does and hovered your mouse to find out? If yes, you’ve seen a tooltip. This plugin extends the concept to allow developers to associate a tip with an element in world.

To do so is quite simple, the following functions are provided with the plugin:

int Add(string text, ImmlElement element)
void Remove(int id)
void SetText(int id, string text)

To make use of these, I’ve added 2 lines to _updateStock in the UpdateStocks script:

--update the volume tooltip	
id = lastTradeVisual:get('tooltipId')
tooltipplugin:settext(id, 'Volume: '..volume)

…and 3 lines to _generateStock in the GenerateStocks script:

--store a define value on the last trade to represent volume for the tooltip
lastTradePrim:set('volume', volume)
id = tooltipplugin:add('Volume: '..volume, lastTradePrim)
lastTradePrim:set('tooltipId', id)

The end result still looks similar to before, but we now get tooltips when hovering:

Download the updated IMML here: stock-ticker.imml

VastPark OpenGL “Army of Craig” Demo from VastPark on Vimeo.

Yes. It is a little strange.

In it’s simplest form the IMML for the VNC Plugin will look something like this:

<Plugin Name="VncPlugin" Enabled="True" 
Source="http://content.vastpark.com/VastParkWS/get.vpws?publisher=craigomatic&amp;name=VncPlugin&amp;domain=vastpark&amp;context=park">
	<Element Name="TargetElement"/>
	<Element Name="OnPasswordRequired"/>
	<Parameter Key="Uri" Value="the-vnc-server-address.com"/>
	<Parameter Key="Port" Value="5900"/>
 	<Parameter Key="PasswordRequired" Value="OnPasswordRequired"/>
</Plugin>
<Script Name="OnPasswordRequired">
    function main(obj, args)
        vncplugin:setpassword('pass') --hardcoding password is bad, you should ask the user to enter one!
    end
</Script>
<Primitive Type="Box" Name="TargetElement" Size="1,1,1"/>

Here’s one I prepared earlier (well, Adrian did most of the work…):

Plugin Parameters

Uri

The host address of the VNC server. You should avoid using the scheme at the start of this address (ie: don’t put the http://)

Port

Defaults to the VNC default of 5900

ConnectionFailed

Name of a Script/Timeline/other ITimelineExecutable element to execute when a VNC connection has failed

PasswordRequired

Name of a Script/Timeline/other ITimelineExecutable element to execute when a password is required to connect to the VNC server

UpdateFrequency

The number of milliseconds to wait before automatically refreshing the remote screen when ManualUpdate is false. Defaults to 500.

ManualUpdate

True/False. When true, you need to call the vncplugin:requestupdate(true) for a fullscreen update. Defaults to False

You can download an example IMML document here: basic-vnc.imml and view the source code for the VNC Plugin over here: http://vastpark-svn.cvsdude.com/public/trunk/Plugins/Plugin.VNC/

A good free windows VNC Server is TightVNC

Yesterday as part of the many happenings during the Virtual Worlds Down Under 09 event, we made the source code for the core VastPark libraries available to the public

The source is pure C# targeting .NET 3.0, licensed under GPL and is available for anonymous access at this address:

http://vastpark-svn.cvsdude.com/public/

Be sure to check out Sample projects\read first.txt for information in acquiring and setting up 3rd party dependencies to avoid losing hair getting the code to compile

Many thanks to CVSDude for supporting us with hosting and you can find out more about VastPark’s open source philosophy here.