Collisions and size

When I create a Collision I must specify the size vector. But I want the User to be able to specify any mesh and just state whether it's a box or sphere (I'm just interested in boxes and spheres as dynamic objects). So I acutally don't know the size and I haven't find a method to determine it. (Is there one?)

So what can I do to solve this problem? Is there any way to detect the size of my mesh or does ogrenewt this somehow by it's own?

For boxes you can use the AABB of the mesh (Mesh::getBounds) and for a sphere you can use the radius (Mesh::getBoundingSphereRadius), or if you want the sphere to be an ellipsoid you can use the AABB too here (halfed on each axis)

Ah, ok, thanks. I'll give it a try.
By the way: In ogreOde there was a TreeMesh for static Objects, which have a more complex form than boxes, cylinders and co. Is there something aquivalent in OgreNewt?

Yes, its the TreeCollision in OgreNewt.

Hey Charlie: if you want to specify the size of your entity, do this:

psuedocode:

get the bounding box of the entity
get the scale of its node
get the extent of the entity ((box.Max() - box.Min) * scale)
now, you need to get the scale necessary to set entity to 'size' (size is a Vector3), like this:

Vector3 scale = size / extent;

Now set the scale of the node and use that size to create your collision body. This is a much easier way of envisioning size of entity in a physics engine, rather than having to deal with some arbitrary node scale, this can calculate it for you.