[ODE] ODE-GIMPACT performance and advices

Flavien Brebion f.brebion at vrcontext.com
Fri Oct 27 02:40:53 MST 2006

Pierre Terdiman wrote:

>I don't understand this, really. Who cares about physics / collisions in a
>level editor? If the level designer is moving a building in a level editor,
>there are usually no collisions at all.
>As far as I can see there are really only two cases:
>- static meshes (the level, will never ever move in the game - because it
>would break the precomputed lighting solution, the AI navigation meshes,
>etc, etc)
>- dynamic meshes (always moving)
>I don't see the point in optimizing for "pseudo static" objects, because
>there are really not the common case.
Thank you for saying this, i had some troubles to explain this clearly.. 
but that's completely my opinion.

>So, transforming *all* the vertices ahead of time is not really "better", it
>all depends on what happens during the actual queries. Transforming ahead of
>time is "eager evaluation", transforming when needed is "lazy evaluation".
>"Eager" is usually better for small meshes, "lazy" is usually better for big
>ones. Pros & cons, as usual.
Agreed, that's why i believe GImpact is more oriented towards high 
amount of simple tri-meshes, as opposed to a small amount of complex 
ones ( which would be what i'm primarily interested in ).

>>Otherwise, it looks very good and seems more robust than Opcode's
>>trimesh code.
>I assume this means "Opcode's trimesh and whaveter contact generation has
>been added on top of it in ODE".....
>Opcode doesn't do contact generation (narrow phase), it only does the
>midphase. As far as I know there is no robustness issue there :)
Yeah, sorry for that, you are of course right. Let's just say that the 
opcode integration in ODE is not very robust.

>About GIMPACT, I would be very very interested to see how it performs with
>"real" meshes. Like, I don't know, a table against a Quake-level. That would
>be sweet. I'm definitely going to try it, as soon as I get some time.
If you are doing those comparison tests, please post the results in this 
mailing list, i would very much be interested in seeing them.

F. Brebion

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