Collision Detection Queries

Hi All,

I have been working with OGRE for last 2 months, but just started using OGREODE .

I have a terrain with 20000+ trees and the player walks over the terrain. Now i want to detect collision between player and the trees.

What i have decided is i when adding player and those 20000 trees, i will add their geometries into "world space" and will register collision listener. Now two thoughts come to my mind:

1) Is it a good way to register geometries of 20000 trees ? Or we can do something better ? ( Anything other than grouping trees into bunches and using a single geometry for a bunch ? )

2) How can i create collision meshes for the trees ? So as to drop polygon count ?

Im using paged geometry to render trees. So i create only one tree entity but put it randomly over terrain. Here is the code:

TreeLoader3D *treeLoader = new TreeLoader3D(pg_trees, TBounds(0, 0, 1500, 1500));

pg_trees->setPageLoader(treeLoader);

//Load a tree entity
Entity *myEntity = mSceneMgrG->createEntity("Tree", "tree2.mesh");

//Randomly place 20,000 copies of the tree on the terrain
Vector3 position;
Radian yaw;
Real scale;
for (int i = 0; i < 20000; i++){
yaw = Degree(Math::RangeRandom(0, 360));
position.x = Math::RangeRandom(0, 1500);
position.z = Math::RangeRandom(0, 1500);
position.y = HeightFunction::getTerrainHeight(position.x, position.z);

scale = Math::RangeRandom(0.5f, 0.6f);

treeLoader->addTree(myEntity, position, yaw, scale);
}

So how to register tree geometry with ODE Space so that trees are collidable ?

Further in above code i do not create a scene node for trees. While EntityInformer::createSingleStaticBox() function it looks for scenenode of entity whose geometry is to be made:

BoxGeometry* EntityInformer::createSingleStaticBox(World *world, Space* space)
{
BoxGeometry* geom = new BoxGeometry(getSize(), world, space);

geom->setPosition(_node->getPosition());
geom->setOrientation(_node->getOrientation());

return geom;
}

Now since there is no scene node, this code wouldnt work.

Can anyone tell what to do here ?

Thanks

you can try to create a geometry for every tree. therefor you need to create a scenenode for every tree, that should be no problem as you already have the positions. then you can add a geometry for every tree using a space you created for them and espacially call space->setInternalCollsions(false);
that should dramatically increase the computation speed. if thats not fast enough try to put all geometries to sleep that are further away than a certain distance and wake them when they get in range.