[Opensim-dev] Refactoring SceneObjectGroup - Introducing Components
adam at deepthink.com.au
Fri Dec 11 12:47:56 CET 2009
I've got a fairly complicated proposal to deliver here today - the short of it is; I'd like to go ahead and replace the current Scene Object representation model - at a fairly comprehensive & complete level. Some of you have had the misfortune of working with SceneObjectPart/SceneObjectGroup and should understand what I am talking about.
There are several stages to this proposal - but I would like to talk about today the first big one (and a small outline of the larger project - the reason for this being some of the later details require a little more nutting out before I have a complete proposal for them).
So - the larger proposal in a nutshell; I would like to:
* Merge SceneObjectGroup & SceneObjectPart
* Enable full inheritance & linking (ie, hierarchical linking)
* Make programming with SceneObjects possible & reasonable from the outside (ie have a clean API).
* Provide the ability to extend SceneObjects with "components" to introduce new properties and behaviours.
The item I'd like to talk about today would be implementing Components. Components are small C# classes that may be attached to any SceneObject arbitrarily.
A component is any class inheriting from IComponent - IComponent carries only two properties; a serialisation property (returns the current 'state' for serialisation purposes), and a type property (which recognises the 'type' of component that it is) - components allow you to attach arbitrary data to an object for the purposes of interacting with a region module. For instance, a "Mesh" module (which is my current best example) would have a MeshComponent that included all the extra data to tag an object with related to meshes - which would get serialised and passed around with the main object. When deserialized - a "Factory" handles making sure the MeshComponent is deserialized with the main object.
I've attached a document which is my current state of the whole proposal which includes some examples & more detail. Please note that Phase 2 is not finalised yet - and some decisions were discussed about changing two facets in particular.
* Enabling inheritance of components+sceneobject to make speedy-classes for common use cases (eg PrimObject inherits PrimComponent and SceneObject)
* Allowing more than one factory potentially; for manufacturing said speedy-classes.
* Note that these shorthand classes would still use the standard .Has / .Get methods; they would just return 'this' where the particular component type is concerned.
To begin with - I would like to implement components as an extra non-serialised property of the SceneObjectPart; this will occur very shortly after 0.7 is tagged; which I would like to do once ROBUST covers all the main services (I heard something about late-december/early-jan); this first stage should not break anything in particular - however once that Is complete, I would like to migrate properties into components in order to modularised the codebase better.
An example of this would be PrimData - primdata is unique to the Second Life use case, and irrelevant to others; in this case, we'll move PrimData into a commonly accessed component (eg "SceneObject.Get<PrimData>.Hollow = 0.9f;") - once the move to components is complete for the common data; then creating the final SceneObject class which merges SceneObjectGroup+Part should be a fairly painless process.
Please take a read of the document attached for more information - and I am very keen to hear anyones thoughts as to use cases that this model will make more difficult; or could not support. The goal with this project is to make OpenSim support more with less - allowing third party modules to really take OpenSim as a framework to the next level; and make a more modular server for other clients & platforms.
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