Revision as of 11:28, 4 July 2014

Introdution

justincc's notes on alternative possibility for materials implementation

Background

Materials are serialized OSD.

Persistence points

If materials data needs to be explicitly persisted rather than always done when changed, then this needs to be done at the following points.

Serialization points

• copy taken into user inventory
• copy taken into prim inventory (could be delayed further but would require deep inspection of a prim's inventory items via UuidGatherer).
• region cross
• teleport (if on attachments)
• IAR saving
• OAR saving

Region data points (i.e. writing to columns in the region database).

• simulator shutdown.
• periodic persistence. At the current time, prim attributes are periodically persisted to the database to avoid too much loss on simulator crash or unclean shutdown for other reasons (somebody accidentally hits ctrl-c, power goes out, etc.).

Approaches

Store materials data in a prim's dynamic attributes

Materials are stored in the prim's dynamic attributes whenever changed.

Pros

• All mechanisms required to persist dynamic attributes to both serialization and region database are already implemented and active.

Cons

• Duplication of data if multiple prims have the same material.
• CPU cost of [de]serialization. Whether this is a significant impact requires measurement, not assumption.

Store materials data as temporary assets until persistence definitely required

Materials are kept as temporary assets and only persisted when required.

Cons

• All possible persistence triggers need to be hooked by the module. It might be possible to simplify this by hooking at the point where existing code asks for an object to be serialized, though this won't cover the case of simulator shutdown.
• Temporary assets don't need to be managed but have the potential to flood the simulator's disk asset cache.
• Materials still suffer an extra serialization cost, though this may be negligible (requires benchmarking).

Pros

• Materials can be rapidly changed without persistent asset storage overhead.

Store materials data in memory cache until persistence definitely required

Materials are kept in a purely in memory cache and only added to the asset service when required

Cons

• All possible persistence triggers need to be hooked by the module. It might be possible to simplify this by hooking at the point where existing code asks for an object to be serialized, though this won't cover the case of simulator shutdown.
• Cache needs to be managed (chiefly removal of items when no longer required).

Pros

• Materials can be rapidly changed without [de]serialization or asset storage overhead.