Rustlight

Physically-based rendering engine implemented with Rust.

How to use it

You can easily uses Rustlight via the provided command line tool (via examples/cli.rs):

$ cargo run --example=cli --release -- -h
rustlight 0.2.0
Adrien Gruson <[email protected]>
A Rusty Light Transport simulation program

USAGE:
    rustlight [FLAGS] [OPTIONS] <scene> [SUBCOMMAND]

FLAGS:
    -d               debug output
    -h, --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
    -a <average>            average several pass of the integrator with a time limit ('inf' is possible)
    -s <image_scale>        image scaling factor [default: 1.0]
    -m <medium>             add medium with defined density [default: 0.0]
    -n <nbsamples>          integration technique
    -t <nbthreads>          number of thread for the computation [default: auto]
    -o <output>             output image file

ARGS:
    <scene>    JSON file description

SUBCOMMANDS:
    ao                           ambiant occlusion
    direct                       direct lighting
    gradient-path                gradient path tracing
    gradient-path-explicit       gradient path tracing
    help                         Prints this message or the help of the given subcommand(s)
    light                        light tracing generating path from the lights
    path                         path tracing generating path from the sensor
    path_kulla                   path tracing for single scattering
    plane_single                 Prototype implementation of 'Photon surfaces for robust, unbiased volumetric
                                 density estimation'
    pssmlt                       path tracing with MCMC sampling
    uncorrelated_plane_single    Prototype implementation of 'Photon surfaces for robust, unbiased volumetric
                                 density estimation'
    vol_primitives               BRE/Beam/Planes estimators
    vpl                          brute force virtual point light integrator

For example, to use path tracing using 128 spp:

$ cargo run --example=cli --release --features="pbrt openexr" -- -a inf -n 128 -o path.pfm ./data/cbox.json path

Other examples (wasm, viewer) are planned.

Optional Features

It is possible to activate/desactivate some features of rustlight depending of your needs:

• image(*): load and save LDR images (via image)
• openexr: load and save EXR images (via openexr-rs)
• pbrt(*): read PBRT files (via pbrt_rs) [Not that only support a subset PBRT primitives]
• mitsuba(*): read Mitsuba files (via mitsuba_rs) [Not that only support a subset Mitsuba primitives]
• progress-bar(*): show progress bar (via pbr)
• embree: fast intersection (via embree-rs)

(*) These features are activated by default.

Features

For now, these are the following features implemented:

• Integrators (most of them using a common graph to represent the light transport):
  • Ambiant occlusion
  • Direct with MIS
  • Path-tracing with NEE
  • [*] Gradient-path tracing [1]
  • Primary-sample space MLT [2]
  • Energy redistribution PT (in PSS) [10]
  • Light tracing
  • Virtual Point Light
• Special volumetric integrators (via vol_primitives):
  • Beam radiance estimate (2D kernel) [3]
  • Photon beams (1D kernel) [4]
  • [*] Photon planes (0D kernel) [5]
  • [*] Naive Virtual ray light [6]
• Special single scattering intergrators:
  • (Un)correlated photon planes [7]
  • Kulla importance sampling [8]
• Filtering:
  • Image-space control variate with uniform and variance-based weights [7]
• Materials:
  • Diffuse
  • Phong lobe
  • Specular
• Emitters:
  • Multiple tri-mesh lights support
  • Point, Directional and Envmap
• Volumes:
  • Infinite homogenous participating media
• Phase functions:
  • Isotropic

[*] Techniques that could contains bugs or are incomplete (only naive implementation)

Rendering

Roadmap

Rendering algorithms for path-tracing:

• use the explict layout to do implement gradient-domain path tracing
• fixing gradient-domain path tracing: seems to have wrong gradient when the light source is not visible from the base path
• gradient-domain path reuse

Other rendering features:

• Materials: glass, microfacet with Beckert distribution.
• Emitters: Environmental and point lights
• Scene format support: PBRT

Inspirations

This code has been inspired from several repositories:

• rs_pbrt project: https://github.com/wahn/rs_pbrt
• the blog post from Brook Heisler: https://bheisler.github.io/post/writing-raytracer-in-rust-part-1/
• tray_rust project: https://github.com/Twinklebear/tray_rust
• mitsuba: https://github.com/mitsuba-renderer/mitsuba

References

[1] Kettunen et al. "Gradient-domain path tracing" (SIGGRAPH 2015)
[2] Csaba et al. "A simple and robust mutation strategy for the metropolis light transport algorithm. (CGF 2002)
[3] Jarosz et al. "The beam radiance estimate for volumetric photon mapping" (EG 2008)
[4] Jarosz et al. "Progressive photon beams" (SIGGRAPH Asia 2011)
[5] Bitterli and Jarosz "Beyond points and beams: Higher-dimensional photon samples for volumetric light transport" (SIGGRAPH 2017)
[6] Novak et al. "Virtual ray lights for rendering scenes with participating media" (SIGGRAPH 2012)
[7] Rousselle et al. "Image-space control variates for rendering" (SIGGRAPH 2016)
[8] Deng et al. "Photon surfaces for robust, unbiased volumetric density estimation" (SIGGRAPH 2019)
[9] Kulla et al. "Importance Sampling Techniques for Path Tracing in Participating Media" (EGSR 2012)
[10] Cline et al. "energy redistribution path tracing" (SIGGRAPH 2012)