[ODE] ODE's speed

[Thomas Grimes]

I was just wondering why, like for example, when you stack so many boxes (10 
for me) that any more after that the simulation will slow WAY down and every 
other box you stack it just goes slower. Also like in the crash example, 
there are a good number of boxes stacked for you to ram into with the car. 
That demo really goes slow from so many boxes stacked. And when you crash 
into the boxes, for a few seconds it's just extremely slow. Now I know my 
CPU isn't the fastest out there (600MHz) but it seems like something simple 
like this shouldn't go so slow. I just read some of the notes from the 
keynotes from id software at QuakeCon 2003 today and they mention their 
physics engine can stack at least 100 boxes for example and have the player 
shoot some of them off making all of the other boxes fall down realistically 
and with out bringing the engine down to a slideshow speed. And this is with 
all the other game stuff and graphics stuff going on at the same time! They 
mention that no other phsyics engine can do this without going at snail 
speed. That seems pretty cool. Anyway, I'd just like to know what is going 
on that makes the physics engine (ODE) go so slow when there are a number of 
boxes, or anything really, stacked. I'd like to optimize ODE using SSE and 
stuff but I just don't know when I can get around to it. :)

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