Re: multithreading issues and the scene graph

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Angus Dorbie (dorbie++at++sgi.com)
Tue, 02 Nov 1999 16:37:19 -0800

Performer does this for pfDCSs but you must update them in the Performer
application process. You then don't have to worry about the propagation
of data through cull & draw. So the thing you have to worry about is the
synchronous running of your calculations and data propagation to the
application process. In part this is handled by performer
multiprocessing if you use a 'compute' process. You should read the
manual on pfmultiprocess for more info. You certainly have to worry
about this stuff.

Cheers,Angus.

Anthony Bavuso wrote:
>
> I have a questions regarding multithreading, mutual exclusion, and the scene
> graph.
>
> I am designing a prototype flight simulator. I have created a class to
> represent visible dynamic models (models that move) in the simulation that
> run in their own thread of execution (using pthreads). This class called
> DynamicModel has a pointer to a pfDCS and a child pfNode for the geometry
> which are both children of the root scene graph node.
>
> The DynamicModel model objects updates the pfDCS node to alter model
> position in its own thread and hence asynchronously to performer traversing
> the scene graph.
>
> There are obvious problems that this could cause. For example the
> DynamicModel may be writing to the pfDCS node while performer is trying to
> read it. Problems solved by using some kind of semaphore, mutex, lock, etc.
>
> My question is, Does performer have built-in to the pfDCS class and-or its
> parent class, come kind of locking mechanism to prevent these problems? Can
> you point me to where I could find documentation on this issue?
>
> Also if the locking capability is not built in, would it be a good idea to
> derive a new class from pfDCS that incorporates this functionality? Has
> anyone done this successfully?
>
> Thanks.
>
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"Success is the ability to go from one failure to another with
 no loss of enthusiasm."    -    Winston Churchill.


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