[Task] Terrain Perception should finalize before other messages are sent

[Spydrouge]

• Status: Game initializes pretty durn reliably at the moment.
• Downgraded from bug/task to minor/task after fixing the biggest problems.
• Extended from #48
• Update: This task may actually have been repaired in the course of attempting to solve #65 because we removed some unnecessary calls to functions that might have tried to notify the OAC of the update

We have used this issue to track & managed to cut down on race conditions, in most places with logic and in one or two places with hacks (we delayed 1 sec, and labeled it with a TODO)

It may also help to add some some logic to the message system to delay in sending some messages until after some important initialization ones have fired. For example it will make sense to hold all terrain altering messages until the finalized terrain perception message has been sent.

[linas]

In general, it is bad form for the sender to try to make up for deficiencies in the receiver. Inn this case, it sounds like all terrain-altering messages should go into a single terrain queue, and be processed in order, one at a time. I mention queues because these have the built-in locking that guarantees a first-in, first-out order. If you don't use aa queue, then you shoul use some ad-hoc lock so that no new messages are handled until terrain init releases the message.

Also: keep in mind that the long-term strategy is to switch to ROS for messaging. whatever fixes are applied today, they should still be valid after some future move to ROS.

(This does beg the question: are there any projects anywhere that add ROS to game-worlds?)

[linas]

Never mind. Ignore my last question.

The only informative discussion I could find was this: http://www.quora.com/Should-I-use-Blender-Game-Engine-or-Unity-3D-to-build-a-robot-simulation

The only other thing I could find basically implied that gazebo is coming along nicely, and that if we wait patiently, it might turn into a game engine someday in the future ...