Example: Add shader-based ray tracing

[gkjohnson]

• Pack the BVH array, indices, positions into shader-readable data (data textures needed?)
• Implement first hit ray cast logic in a shader
• Provide easily extensible / reusable template and shader snippets to enable custom raytracing logic.
• Render raytraced result
  • https://raytracing.github.io/books/RayTracingInOneWeekend.html
  • https://raytracing.github.io/
  • https://twitter.com/Michael_Moroz_/status/1420896764245184514
  • https://research.nvidia.com/sites/default/files/pubs/2013-09_On-Quality-Metrics/aila2013hpg_paper.pdf
  • https://pbr-book.org/3ed-2018/Primitives_and_Intersection_Acceleration/Bounding_Volume_Hierarchies
  • https://www.scratchapixel.com/lessons/3d-basic-rendering/global-illumination-path-tracing
  • https://agraphicsguy.wordpress.com/2015/11/01/sampling-microfacet-brdf/
  • https://www.arnoldrenderer.com/research/egsr2012_volume.pdf
  • https://computergraphics.stackexchange.com/questions/5152/progressive-path-tracing-with-explicit-light-sampling
  • https://www.youtube.com/watch?v=oHLR287rDRA
  • https://www.youtube.com/watch?v=TbWQ4lMnLNw
  • http://courses.washington.edu/arch481/1.Tapestry%20Reader/4.Rendering/9xPath%20Tracing/0.default.html

Planned Features

• Importance sampling function of normal distribution function
• Direct area light sampling
• Diffuse / Metal objects
• Depth of Field
• Anti Aliasing
• Translucent / Transmissive objects?
• Denoiser? (shader only? May require MRT, no DoF)
• Blue noise sampling?
• Material index
• Dragon / full environment scene (architectural? game scene?)
• Tiled-approach for expensive shader-based path tracing

Future

• Textures

Toggles

• Resolution scale
• Number of bounces
• Material properties (including emission)
• Area light positioning
• Aperture size

Notes

#### Points of Interest - antialiasing (wk 1) - area lights (wk 2) - ambient occlusion (wk 1) - depth of field (wk 2) - caustics (??) - importance sampling / monte carlo sampling (wk 3) #### Weekend 1 **Anti aliasing** - Jitter the rays / camera for anti aliasing / multiple samples per pixel - Divide out total samples per pixel at the end. **Diffuse Sampling** - Add limit for max sampling depth - Must apply gamma correction after the fact for display - Must model energy absorption in the form of color - Start the ray a small step away from the surface to avoid self-intersections - Provides correct lambertian scattering model - Ensure we don't create a scatter ray of `0, 0, 0`.

[MaartenBreeedveld]

Maybe you could team up with erichlof from THREE.js-PathTracing-Renderer.

[gkjohnson]

Thanks! I'm familiar with the project and it looks great. My goal with this demo would just be to produce a basic proof-of-concept demo to show how it can be done with the BVH class rather than a full blown high quality renderer.