jbikker / bvh_article

Code accompanying the blog post on bvh construction.

Code for "How to Build a BVH"

INSTRUCTIONS: Open the "_ bvhdemo.sln" file (all the way at the top!), and make one of the 10 projects the active project.

Note: project files are for Visual Studio 2019; they will convert without issues to 2022 though.

Each project implements one of the 10 articles:

part 1, basics:
https://jacco.ompf2.com/2022/04/13/how-to-build-a-bvh-part-1-basics
...Which explains how to set up a minimal but working BVH in about 300 lines of code.
Project: basics.vcxproj, files: basics.cpp, basics.h

part 2, faster rays:
https://jacco.ompf2.com/2022/04/18/how-to-build-a-bvh-part-2-faster-rays
...in which rays are traced faster, at the expense of BVH build time.
Project: faster.vcxproj, files: faster.cpp, faster.h

part 3, quick builds:
https://jacco.ompf2.com/2022/04/21/how-to-build-a-bvh-part-3-quick-builds
...explains how a high-quality BVH can be constructed rapidly.
Project: quickbuild.vcxproj, files: quickbuild.cpp, quickbuild.h

part 4, animation:
https://jacco.ompf2.com/2022/04/26/how-to-build-a-bvh-part-4-animation
...in which various forms of animation are applied to BVHs.
Project: animation.vcxproj, files: animation.cpp, animation.h

part 5, TLAS & BLAS:
https://jacco.ompf2.com/2022/05/07/how-to-build-a-bvh-part-5-tlas-blas
...describes how a lot of BVHs can be made into one.
Project: toplevel.vcxproj, files: toplevel.cpp, toplevel.h

part 6, TLAS & BLAS part 2:
https://jacco.ompf2.com/2022/05/13/how-to-build-a-bvh-part-6-all-together-now
...which completes the discussion of article 5.
Project: alltogether.vcxproj, files: alltogether.cpp, alltogether.h

part 7, consolidation:
https://jacco.ompf2.com/2022/05/20/how-to-build-a-bvh-part-7-consolidate
...in which the BVH is applied to some nicer renders.
Project: pretty.vcxproj, files: pretty.cpp, pretty.h, bvh.cpp, bvh.h

part 8, whitted:
https://jacco.ompf2.com/2022/05/27/how-to-build-a-bvh-part-8-whitted-style
...completing part 7, with full recursive ray tracing, in real-time.
Project: whitted.vcxproj, files: whitted.cpp, whitted.h, bvh.*

part 9a, GPGPU:
https://jacco.ompf2.com/2022/06/03/how-to-build-a-bvh-part-9a-to-the-gpu
...which is really a GPGPU tutorial, using BVHs as an example.
Project: gpgpu.vcxproj, files: gpgpu.cpp, gpgpu.h, bvh.*

part 9b, 'massive':
https://jacco.ompf2.com/2022/06/15/how-to-build-a-bvh-part-9b-massive
...series finale, with TLAS & BLAS on the GPU. Also: GL/CL interop.
Project: massive.vcxproj, files: massive.cpp, massive.h, raytracer.cl.

NOTE: All projects share the same template files and build directories.
DISCLAIMER: None of this is supposed to be 'production quality'.
LICENSE: This code is covered by the Unlicense. Feel free, no strings.

P.S.: Follow me on Twitter, @j_bikker.

bvh_article's Issues

ray direction calculation

Hi, I am a little confused about the way to calculate orientation calculation.
in chapter2:
https://github.com/jbikker/bvh_article/blob/89bf112b7ca8c277ac0a311119aa2e29d5ee41f1/faster.cpp#L277C1-L279C57

ray.O = float3( -1.5f, -0.2f, -2.5f );
float3 pixelPos = ray.O + p0 + (p1 - p0) * ((x + u) / (float)SCRWIDTH) + (p2 - p0) * ((y + v) / (float)SCRHEIGHT);
ray.D = normalize( pixelPos - ray.O ), ray.t = 1e30f;

Why need to add ray.O for pixelPos, and minus the ray.O to calculate ray,D. It seems the rays are emitted from (0,0,0), but the ray origin point is still ( -1.5f, -0.2f, -2.5f )

and in chapter1:
In chapter1:
https://github.com/jbikker/bvh_article/blob/89bf112b7ca8c277ac0a311119aa2e29d5ee41f1/basics.cpp#L182C1-L184C41

float3 pixelPos = p0 + (p1 - p0) * (x / (float)SCRWIDTH) + (p2 - p0) * (y / (float)SCRHEIGHT);
ray.D = normalize( pixelPos - ray.O );

there is different calculation for pixelPos (no ray.O added)

Missing bounds by default [ bug ]

Maybe add a default bounds initialization after this line to use the bvhNode[0] bounding box. If SetTransform() is not called on BLAS, the TLAS intersection code will most probably crash.

bvh_article/toplevel.cpp

Line 70 in d714193

Build();

Tutorials are 403 Forbidden

Hi, I loved your tutorials on BVH. I was saving them for reference. And it appears that the site is not inaccessible anymore: https://jacco.ompf2.com/2022/04/13/how-to-build-a-bvh-part-1-basics/
Getting 403 Forbidden.

Could be a temporary glitch

missing macros in win_tiny.h

Thanks for your great blog posts, I was just trying to play around with the code a bit this evening.

Immediately had troubles to get this to compile in a fresh installation of VS2022. Namely the DEFINE_ENUM_FLAG_OPERATORS from winnt.h seems missing in the win_tiny.h nowadays. Including the bigger windows.h again and commenting the tiny header works again:

#include "windows.h"
// #include "lib/win_tiny.h" // windows.h replacement for faster builds

bvh_article/template/precomp.h

Line 79 in c127c63

#include "lib/win_tiny.h" // windows.h replacement for faster builds

I'm on win11 with a fairly recent sdk version: 10.0.22621.0 that I just downloaded. Thought I'll leave a quick note here before others spend hours on figuring out what was missing.

Cheers,
Thomas