Single-header BVH construction and traversal library written as "Sane C++" (or "C with classes"). The library has no dependencies.
A Bounding Volume Hierarchy is a data structure used to quickly find intersections in a virtual scene; most commonly between a ray and a group of triangles. You can read more about this in a series of articles on the subject: https://jacco.ompf2.com/2022/04/13/how-to-build-a-bvh-part-1-basics .
Right now tiny_bvh comes with two builders:
BVH::Build: Efficient plain-C/C+ builder which should run on any platform.BVH::BuildAVX: A highly optimized version of BVH::Build for Intel CPUs.
Once a BVH is constructed, it may be refitted in case the triangles moved using BVH::Refit. Refitting is substantially faster than rebuilding and works well if the animation is subtle. Refitting does not work if polygon counts change.
A constructed BVH can be used to quickly intersect a ray with the geometry, using BVH::Intersect.
The library tiny_bvh.h is designed to be easy to use. Please have a look at tiny_bvh_test.cpp for an example. A Visual Studio 'solution' (.sln/.vcxproj) is included, as well as a CMake file. That being said: The examples consists of only a single source file, which can be compiled with clang or g++, e.g.:
g++ -std=c++20 -mavx tiny_bvh_test.cpp -o tiny_bvh_test
The single-source sample ASCII test renderer can be compiled with
g++ -std=c++20 -mavx tiny_bvh_renderer.cpp -o tiny_bvh_renderer
The cross-platform fenster-based single-source bitmap renderer can be compiled with
g++ -std=c++20 -mavx tiny_bvh_fenster.cpp -o tiny_bvh_fenster
Thanks to Eddy L. O. Jansson for help with g++ and clang.
The current version of the library is a 'prototype'; please expect changes to the interface. Once the interface has settled, more functionality will follow. Plans:
- Spatial Splits (SBVH)
- Conversion to GPU-friendly format
- Collapse to 4-wide and 8-wide BVH
- Optimization of an existing BVH using treelet reinsertion
- OpenCL traversal example
- 'Compressed Wide BVH' data structure (CWBVH)
- Efficient CWBVH GPU traversal
- TLAS/BLAS traversal with BLAS transforms
These features have already been completed but need polishing and adapting to the interface, once it is settled. CWBVH GPU traversal combined with an optimized SBVH provides state-of-the-art #RTXOff performance; expect billions of rays per second.
Questions, remarks? Contact me at bikker.j@gmail.com or on twitter: @j_bikker, or BlueSky: @jbikker.bsky.social .
This library is made available under the MIT license, which starts as follows: "Permission is hereby granted, free of charge, .. , to deal in the Software without restriction". Enjoy.