lumo 0.2.0-alpha

Lumo

Lumo is a CPU based multithreaded rendering engine. Made with the goal of learning Rust and physically based rendering :) The renderer is designed to be as modular as possible such that adding new features or algorithms is straightforward.

Features

• Area light sampling
• Path tracing with next event estimation
• Microfacet BSDF with Beckmann and GGX normal distribution functions
• Multiple importance sampling from VNDF for GGX
• Disney diffuse BRDF with energy normalization used in Frostbite
• Vertex and normal parsing from .OBJ files
• Stratified sampling
• kd-tree with SAH
• Perlin noise generator

Usage

Once the repository is cloned, the examples/ folder contains scenes. To run the hello_sphere.rs example execute the command:

cargo run --example hello_sphere

The renderer can be configured either through its setter methods or partially through the CLI:

Usage: hello_sphere [-s <samples>] [-t <threads>] [-w <width>] [-h <height>] [-d]

Optional CLI configuration of renderer. Renderer setter methods have priority.

Options:
  -s, --samples     number of samples per pixel (defaults to 1)
  -t, --threads     number of threads used (defaults to all)
  -w, --width       width of the rendered image (defaults to 1000)
  -h, --height      height of the rendered image (defaults to 1000)
  -d, --direct      use direct light integrator instead of path tracing.
  --help            display usage information

Using the API

The hello_sphere.rs example is written as follows:

use lumo::*;
use lumo::tracer::*;
use glam::DVec3;

fn main() -> Result<(), png::EncodingError> {
    let camera = Camera::default();
    let mut scene = Scene::default();

    scene.add(
        Plane::new(
            DVec3::NEG_Y,
            DVec3::Y,
            Material::diffuse(Texture::Solid(srgb_to_linear(190, 200, 210)))
        )
    );

    scene.add(
        Sphere::new(
            8.0 * DVec3::Y + 1.5 * DVec3::NEG_Z,
            4.0,
            Material::Light(Texture::Solid(srgb_to_linear(255, 255, 255)))
        )
    );

    scene.add(
        Sphere::new(
            DVec3::ZERO,
            1.0,
            Material::diffuse(Texture::Solid(srgb_to_linear(0, 0, 255)))
        )
            .scale(0.3, 0.3, 0.3)
            .translate(0.0, -0.7, -1.5)
    );

    let mut renderer = Renderer::new(scene, camera);
    renderer.set_samples(36);
    renderer.render()
        .save("hello.png")
}

TODO/WiP

• Firefly reduction (better sampling? tone mapping?)
• Isotropic mediums (fog, smoke, clouds, ...)
• Multiple importance sampling in path tracer
• Parallelize kd-tree construction
• kd-tree construction in $n \log n$
• (Texture mapping)
• (Bidirectional path tracing)
• (Subsurface scattering)

References

• Physically Based Rendering
• Ray Tracing in One Weekend
• Moving Frostbite to Physically Based Rendering
• Eric Veach's PhD Thesis
• ekhzang/rpt

Gallery

Stanford dragon with 871K triangles. Rendered in 23 minutes using Intel Xeon Gold 6248. 4096 samples per pixel.

Cornell box displaying reflection and refraction. Rendered in 10 minutes using Intel Xeon Gold 6248. 4096 samples per pixel.