I am experimenting with building a bounding volume hierarchy using only immutable data-structures. I hope to use the tree for broad-phase collision tests in a real-time simulation.
The tree structure is like this:
type BvhTree<'t> =
| Leaf of BvhLeaf<'t>
| Branch of BvhBranch<'t>
| Nil
and BvhLeaf<'t> =
{
Bounds : AABB
Data : 't
}
and BvhBranch<'t> =
{
Bounds : AABB option
Left : BvhTree<'t>
Right : BvhTree<'t>
}
The goal then is to take a list of simulation objects, which all have bounding volumes (just AABBs for now to keep things simple), and produce a reasonably optimal bounding volume hierarchy.
The best tree is defined as the one whose branching nodes have the lowest surface area in total.
Testing every possible tree structure is too slow and simple appending creates a tree that is too lop-sided, giving poor collision test performance. It might also be possible to use the tree from previous simulation states as a starting point to compute the next tree.
Since I am using immutable data, I must build the tree from the bottom up, unlike the approach usually taken (see this excellent set of slides).
I have been unable to find many resources on the topic.
The basic approach I have come up with is to generate a list of trees, one for each simulation object and then recursively merge them until only only one tree remains. At each step the merge is chosen using simple heuristics.
What are some good techniques for doing this?
