https://github.com/ennocramer/lucifer

Lucifer is a physically based renderer, written as a tutorial on how to implement raytracing and pathtracing in Rust.
https://github.com/ennocramer/lucifer

Last synced: 12 months ago
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Lucifer is a physically based renderer, written as a tutorial on how to implement raytracing and pathtracing in Rust.

• Host: GitHub
• URL: https://github.com/ennocramer/lucifer
• Owner: ennocramer
• Created: 2018-01-09T10:20:52.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2018-10-01T12:45:50.000Z (almost 8 years ago)
• Last Synced: 2025-01-19T14:24:18.439Z (over 1 year ago)
• Language: Rust
• Homepage:
• Size: 325 KB
• Stars: 3
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

          
# Lucifer

Lucifer is a physically based renderer, written as a tutorial on how

to implement raytracing and pathtracing in Rust.

![example](example.png)

Lucifer tries to showcase a very clean and easy-to-understand

implementation of the basics of 3D rendering using raytracing.

The first few [commits](https://github.com/ennocramer/lucifer) are

structured as a tutorial, showing the implementation of the core

structures and algorithms of a [path

tracing](https://en.wikipedia.org/wiki/Path_tracing) renderer.

## Building

Lucifer is written in [Rust](https://www.rust-lang.org/) and may,

depending on when you're trying to build it, require on the nightly

release of the Rust compiler.

``` sh

# Install Rust via Rustup

$ curl https://sh.rustup.rs -sSf | sh

# Install nightly release, if necessary

$ rustup install nightly

$ rustup default nightly

# Build lucifer

$ cargo build --release

# Run lucifer to generate the example output

$ cargo run --release example.png

```

## Core Concepts

### Space

Space is represented using the `Vector` and `Point` types, taken from

the [cgmath crate](https://crates.io/crates/cgmath).  `Point`

represents positions in space, while `Vector` represents directions

and distances between points.

A `Ray` is a straight line through space.  It has an origin, a

direction, and a possibly infinite length.  Rays represent the path

photons travel unhindered after being emitted, until interacting

(possibly being absorbed or reflected) with the surface of an object.

An `Intersection` describes a location where a photon hits, and

interacts with, an object. It consists of the point in space where the

intersection occurred, the object's surface's normal vector, the

distance from the photon's origin, and a boolean indicating whether

the surface was hit from the object's inside or outside.

A `Geometry` is the abstraction of a physical shape. It provides

methods for intersections tests between itself and `Ray`s.

### Energy

Light is represented using the `Radiance` structure, which models the

radiant intensity of light coming from a given direction. Radiant

intensity defines the color and brightness of light.

The color of a surface is represented by `Albedo`.  An `Albedo` is a

multiplicative factor for `Radiance`, with the assumption that any

value is between zero and one.  I.e. an `Albedo` cannot increase

`Radiance` and cannot turn `Radiance` negative.

The appearance of a surface is modeled as a set of `Effect`s, each

representing a specific type of interaction between light and the

surface.  The set of `Effect`s is called `Bsdf`.

Each effect is composed of an effect type, a `Distribution`, and some

combination of `Radiance`, `Albedo`, and `Ior`.  There are five

different effects:

  1. **Emission** is light emitted by a surface, independently of

     incoming light. This is the primary `Effect` for light sources.

     Emission is defined by a `Radiance` value and a distribution

     function.

  2. **Diffuse Reflection** is light scattered by the surface.  This

     is the primary `Effect` for rough surfaces.

     Diffuse reflection is defined by an `Albedo` value and a

     distribution function.  The `Distribution` is centered on the

     surface normal

  3. **Specular Reflection** is light reflected by the surface.  This

     is the primary `Effect` for shiny surfaces and mirrors.

     Specular reflection is defined by an `Albedo` value and a

     distribution function.  The `Distribution` is centered on the

     reflected incidence direction.

  4. **Diffuse Refraction** is light transmitted, but scattered by the

     surface. This is the primary `Effect` for light-transmitting, but

     non-transparent objects.

     Diffuse refraction is defined by an `Albedo` value and a

     distribution function. The `Distribution` is centered on the

     mirrored surface normal.

  5. **Specular Refraction** is light transmitted and refracted by the

     surface. This is the primary `Effect` for clear, transparent

     objects.

     Specular refraction can turn into reflection, if the angle of

     incidence is low.

     Specular refraction is defined by an `Albedo` and `Ior` value and

     a distribution function.  The `Distribution` is centered on the

     refracted incidence direction.

The `Material` trait is responsible to compute the surface's

appearance at the point of intersection.  The generated set of

`Effect`s and their attributes can vary depending on the attributes of

the `Intersection`.