[ODE] Collision detection slowdown?

[Nguyen Binh]

>
>
> Power-up : 936 vertices and 312 triangles
> Cylinder : 96 vertices and 32 triangles
> Sphere   : 144 vertices and 48 triangles
> Box      : 36 vertices and 12 triangles


I don't understand why you triangulated primitive shapes?

I was surprised that lowering the resolution to 32x32 didn't improve
> performance
> that much, since it's 16 times less polygons... Normally I don't think
> 2048
> polygons is really that many...



Not so surprise! general trimesh-trimesh collision is the killer. I don't
think there
are any 100% robust and "fast enough" algorithm in this case.


Of course, the thing that may be slowing things down is that the terrain is
> like
> a "sink" and the submaine in my game is always inside it. Picture
> something like
> this in 3D:
>
>
> --                                    --   <-- water surface
>   \        * <-- submarine  __       /
>    \     ___               /  \     /
>     \___/   \____----_____/    \___/       <-- bottom of the sea
>
> So the bounding box test for the terrain with anything would always
> succeed, and
> it would have to check every polygon. The only way to speed it up if
> that's the
> only thing causing the slowdown would be to split the terrain into
> "tiles",
> right? Or is there another way?


There can be some improvement if current trimesh-trimesh use BV tree to quickly
remove triangles (I think Opcode do this job). But I can say: never use
general trimesh
in collision (unless you REALLY have to). Convex trimesh in general could be
used instead.

Any suggestions would be appreciated. Thanks in advance,
>
> J-S
>
> [1] http://www.gamasutra.com/features/20000228/ulrich_01.htm
> --
> ______________________________________________________
> Jean-Sebastien Guay     jean-sebastien.guay at polymtl.ca
>                          http://whitestar02.webhop.org
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--
--------------------------------------------------
Binh Nguyen
Computer Science Department
Rensselaer Polytechnic Institute
Troy, NY, 12180
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