Bounding volume hierarchy

Bounding volume hierarchies are used to support several operations on sets of geometric objects efficiently, such as in collision detection and ray tracing.

Some recent studies[3] indicate that in low-dimensional space, the construction speed can be largely improved (which matches or outperforms the top-down approaches) by sorting objects using space-filling curve and applying approximate clustering based on this sequential order.

Additionally, many specialized methods were developed for BVHs, especially ones based on AABB (axis-aligned bounding boxes), such as parallel building, SIMD accelerated traversal, good split heuristics (SAH - surface-area heuristic is often used in ray tracing), wide trees (4-ary and 16-ary trees provide some performance benefits, both in build and query performance for practical scenes), and quick structure update (in real time applications objects might be moving or deforming spatially relatively slowly or be still, and same BVH can be updated to be still valid without doing a full rebuild from scratch).

To solve these problems (as well as quick structure update being sub-optimal), the new BVH could be built asynchronously in parallel or synchronously, after sufficient change is detected (leaf overlap is big, number of insertions and removals crossed the threshold, and other more refined heuristics).

BVHs can also be combined with scene graph methods, and geometry instancing, to reduce memory usage, improve structure update and full rebuild performance, as well as guide better object or primitive splitting.

Pseudo code for computing pairwise distance between two set of objects and approaches for building BVH, well suited for distance calculation is discussed here [6] BVH can significantly accelerate ray tracing applications by reducing the number of ray-surface intersection calculations.

RT Cores are specialized hardware units designed to accelerate BVH traversal and ray-triangle intersection tests.

The architecture uses dedicated hardware units called Ray Accelerators to perform ray-box and ray-triangle intersection tests, which are crucial for traversing Bounding Volume Hierarchies (BVH).

[9] In RDNA 2 and 3, the shader is responsible for traversing the BVH, while the Ray Accelerators handle intersection tests for box and triangle nodes.

[10] Originally designed to accelerate ray tracing, researchers are now exploring ways to leverage fast BVH traversal to speed up other applications.

These include determining the containing tetrahedron for a point,[11] enhancing grannular matter simulations,[12] and performing nearest neighbor calculations.