[sldev] Optimus Prim vs. Megatrim: "The Big Prim Problem"

Argent Stonecutter secret.argent at gmail.com
Wed Oct 17 10:59:44 PDT 2007


On 17-Oct-2007, at 12:41, Dzonatas wrote:
> Argent Stonecutter wrote:
>> The thing is, as far as the physics engine is concerned, a linkset  
>> 40m across is just as hard to deal with as a single prim 40m  
>> across. A linkset with a hollow is just as bad as a hollow prim.  
>> If the prims are unlinked and magic, what happens if some of them  
>> are deleted? It seems a lot of complexity that will violate the  
>> principle of least astonishment.

> There is a parallelization process that could happen within a sim.  
> The single 40m prim offers no parallelization ability by default by  
> itself. A prim made of smaller prims may be broken up and processed  
> by two (or more) separate render paths on the physics side. With  
> both version available, one optimized megaprim could travel across  
> a sim boundary and be handled physically by both.

Just thinking of the obvious ways this could break makes me want to  
run screaming.

>> I don't see how exposing the complexity to the end user provides  
>> any benefit. As something that the server could to to simplify the  
>> calculations for concave objects under the hood, sure... but the  
>> client doesn't care, it only wants the graphically simplest form.

> It does not need to be exposed. The current state of the viewer  
> would only have such exposure just to give the ability. Beyond  
> that, the viewer can include (in the future) specialized megaprim  
> builders (as sort-of suggested in Aimee's blog -- please review her  
> blog again).

And I'm saying it shouldn't be exposed outside the sim itself. There  
is no reason this kind of optimization - breaking a single prim or  
linkset (they're the same thing as far as the the physics engine is  
concerned, as far as I can tell) into multiple objects for the  
physics engine - should require even transmitting the fact that this  
optimization has taken place to the viewer, or to other sims.



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