# Crate bvh [−] [src]

A crate which exports rays, axis-aligned bounding boxes, and binary bounding volume hierarchies.

This crate can be used for applications which contain intersection computations of rays with primitives. For this purpose a binary tree BVH (Bounding Volume Hierarchy) is of great use if the scene which the ray traverses contains a huge number of primitives. With a BVH the intersection test complexity is reduced from O(n) to O(log2(n)) at the cost of building the BVH once in advance. This technique is especially useful in ray/path tracers. For use in a shader this module also exports a flattening procedure, which allows for iterative traversal of the BVH. This library is built on top of `nalgebra`.

## Example

```use bvh::aabb::{AABB, Bounded};
use bvh::bounding_hierarchy::{BoundingHierarchy, BHShape};
use bvh::bvh::BVH;
use bvh::nalgebra::{Point3, Vector3};
use bvh::ray::Ray;

let origin = Point3::new(0.0,0.0,0.0);
let direction = Vector3::new(1.0,0.0,0.0);
let ray = Ray::new(origin, direction);

struct Sphere {
position: Point3<f32>,
node_index: usize,
}

impl Bounded for Sphere {
fn aabb(&self) -> AABB {
let min = self.position - half_size;
let max = self.position + half_size;
AABB::with_bounds(min, max)
}
}

impl BHShape for Sphere {
fn set_bh_node_index(&mut self, index: usize) {
self.node_index = index;
}

fn bh_node_index(&self) -> usize {
self.node_index
}
}

let mut spheres = Vec::new();
for i in 0..1000u32 {
let position = Point3::new(i as f32, i as f32, i as f32);
let radius = (i % 10) as f32 + 1.0;
spheres.push(Sphere {
position: position,
node_index: 0,
});
}

let bvh = BVH::build(&mut spheres);
let hit_sphere_aabbs = bvh.traverse(&ray, &spheres);```

## Reexports

 `pub extern crate nalgebra;`

## Modules

 aabb Axis Aligned Bounding Boxes. axis Axis enum for indexing three-dimensional structures. bounding_hierarchy This module defines the `BoundingHierarchy` trait. bvh This module defines a `BVH`. flat_bvh This module exports methods to flatten the `BVH` and traverse it iteratively. ray This module defines a Ray structure and intersection algorithms for axis aligned bounding boxes and triangles.

## Constants

 EPSILON A minimal floating value used as a lower bound. TODO: replace by/add ULPS/relative float comparison methods.