How to make Aabb - broccoli

How to make a Aabb

So far we've talked about how aabbs can be stored in a Tree. For example we recommended populating it with BBox<N,&mut T>. But we haven't talked about how you would generate such a struct.

In some dynamic systems, every particle has a position and maybe a radius, and then from the position and radius an aabb can be generated. So what you store in your tree might look something like this:

BBox<f32,&mut Particle>

where Particle might look like this:

struct Particle{
    pos:[f32;2],
    vel:[f32;2]
}

and then in your main loop you might have something like this:

    tree.for_every_colliding_pair(|a,b|{
        a.unpack_inner().repel(b.unpack_inner());
    })

An optimization idea

Provided all the particles are the same size, in order to save on space, your particle could just be :

struct Particle{
    vel:[f32;2]
}

And you could instead use one of the corners of the aabb:

    tree.for_every_colliding_pair(|a,b|{
        let apos=[a.rect.x.start,a.rect.y.start];
        let bpos=[b.rect.x.start,b.rect.y.start];
        repel(apos,a.unpack_inner(),bpos,b.unpack_inner())
    })

Where repel is modified to take the center of the particle as an argument. This works because for the repel() function we just need the relative offset position to determine the direction and magnitude of the repel force. So it doesn't matter that we used the top left corner instead of the center.

broccoli_report

How to make a Aabb

An optimization idea