## Overview
An interactive path tracer implemented in WGSL. Supports multiple sampling methods, physically based materials including micro-facets, and realistic light sources. Primarily written to explore WGSL and the WebGPU API. So it takes some shortcuts and is pretty straightforward.
This is a GPU "software" path tracer, since there is no HW-accel using RT cores, it contains manual scene intersections and hit tests.
- Single megakernel compute pass, that blits the output to a viewport quad texture
- All primitives are extracted from the model -> a SAH split BVH is constructed from that on the host
- Expects GLTF models, since the base specification for textures and PBR mapped pretty nicely to my goals here. So roughness, metallic, emission, and albedo. Textures and the normal map
- A BRDF for these material properties, pretty bog standard. Cosine weighted hemisphere sample for the rougher materials and a GGX distribution based lobe for the specular.
- There is no support for transmission, IOR, or alpha textures
- Balanced heuristic based multiple importance sampling; two NEE rays. One for direct emissives and another for the sun
- Uses stratified animated blue noise for all the screen space level sampling and faster resolves.
- Contains a free cam and mouse look, typical `[W][A][S][D]` and `[Q][E]` for +Z, -Z respectively. `[SHIFT]` for a speed up. The camera also contains a basic thin lens approximation.
- Since WebGPU doesn't have bindless textures, the suggested way of doing textures is a storage buffer. This would require generating mipmaps on the host. I just stack the textures and call it a day here.
- All shader internals are full fat linear color space, that is then tonemapped and clamped to SRGB upon blitting.
## Local setup
```
pnpm install
pnpm run dev
```
`/public` should contain the assets. Just compose the scene manually in `main.ts` position, scale, rotate.
All the included models are licensed under Creative Commons Attribtution 4.0.
## To-do
- Direct lighting NEE from an HDR equirectangular map
### Resources
- [WebGPU specification](https://www.w3.org/TR/webgpu/)
- [WGSL Specification](https://www.w3.org/TR/WGSL/)
- **Jacob Bikker:** [Invaluable BVH resource](https://jacco.ompf2.com/about-me/)
- **Christoph Peters:** [Math for importance sampling](https://momentsingraphics.de/)
- **Jakub Boksansky:** [Crash Course in BRDF Implementation](https://boksajak.github.io/files/CrashCourseBRDF.pdf)
- **Brent Burley:** [Physically Based Shading at Disney](https://media.disneyanimation.com/uploads/production/publication_asset/48/asset/s2012_pbs_disney_brdf_notes_v3.pdf)
- **Möller–Trumbore:** [Ray triangle intersection test](http://www.graphics.cornell.edu/pubs/1997/MT97.pdf)
- **Pixar ONB:** [Building an Orthonormal Basis, Revisited
](https://www.jcgt.org/published/0006/01/01/paper-lowres.pdf)
- **Uncharted 2 tonemap:** [Uncharted 2: HDR Lighting](https://www.gdcvault.com/play/1012351/Uncharted-2-HDR)
- **Frostbite BRDF:** [Moving Frostbite to Physically Based Rendering 2.0](https://media.contentapi.ea.com/content/dam/eacom/frostbite/files/course-notes-moving-frostbite-to-pbr-v2.pdf)
- **Reference Books**: Ray tracing Gems 1 and 2, Physically based rendering 4.0.