[ODE] Terrain: collision test culling

[johnmcTemp at netscape.net]

Thanks for the replies!!

> Gabriel wrote:
>There are a couple of Terrain Collider contribs out there. I grabbed one
>from another LGPL-or-less-strict project and hacked it to suit my
>purposes. It handles a terrain of 2 million triangles without any
>trouble.

Yeah. I saw at least the one in sdk that uses cones (Bennot.. something). If that be one of the ones you refer to, I have considered it, and it will be taken to heart. One thing is that by asking these question, I will begin to understand *HOW* ode works so I can learn to increase performance, instead of just popping in another class. Right now its only a terrain, so sure the terraincollision class will help. But what about later when I add hundreds, if not thousands of objects as well. This questioning of mine helps then too! ;)


Hannes. When I sent a reply to ode, I think I may have had your address
as the reply address. Sorry. ;)

> Hannes wrote:
>have a look at collide/category bits
>http://www.ode.org/ode-latest-userguide.html#sec_10_5_1
>They let you cull collisions early, just before the AABB-test I think.

Will have to read through it. I was doing something similar by setting the
user data within the geom, and testing that data, so this may be a lot cleaner!

>Also you could try to put all your static geometry in one space and
>dynamic (and static you still wanna check against 'static world') in
>another space.
>
>Now when you check for collisions you just collide the dynamic with the
>static and then the dynamic with itself. Thus not checking for
>collisions between static world at all.

Im gonna try this out now. It sounds really cool. If it works, like you say, I will jump for joy!

>I also built my staticspace with subspaces, based on the octree I use
>for rendering.

I am curious. Since spaces are 'unplaceable', if I use a quadtree space, doesnt using subspaces negate the benefits of how a quadtree partions the space??!!! Let me explain: If you didnt have subspaces, then I hope that when an object is tested, it goes down the quadtree, only colliding with objects within collision range of that area. With subspaces, does each subspace have to test with each other subspace, then, the colliding subspaces do there collision between. Would seem like no culling using a division of space like a quadtree would help.  ...I guess this may be an OPCODE thing, I dont know...

- John

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