raytracer

This is a raytracer written in Rust for an apprenticeship project during my freshman year of college.

Crates

As of now, there are several crates in this project:

• raytracer - The raytracer itself, which takes a scene, raytraces it, and outputs it to a file.
• stitcher - A cubemap stitcher. Provided 6 cubemap faces, this outputs a single atlas that can be used by the raytracer.
• sdl - The raytracer's proprietary scene description language, loosely inspired by POV-Ray's. This crate has its own tokenizer, AST, and interpreter for parsing SDL files.

For more information on the SDL (scene description language), please visit its README.

Using

Start by building with cargo build --release -p sdl.

You can render a scene with ./target/release/sdl <source file> [-o <output file>]. For example, you can render fedora.sdl to fedora.png with ./target/release/sdl fedora.sdl -o fedora.png.

To write your own scene, see the sdl README.

Contributions

You are welcome to fork and tinker with this project, but I will not be accepting contributions. Sorry!

Things to research

Since the goal of this raytracer is to be fast, here are some things I want to research more on:

• Acceleration structures
  • Octrees (I have an implementation of this already)
  • BVH (this paper by Nvidia looks like a great resource)
    • This has been implemented!
  • More?
• Better parallelism (currently made possible by Rayon, a data parallelism library)
• Run on the GPU somehow?
  • If not, look into using SIMD for accelerated ray intersection math

Things to add

Along with the above research considerations, here are some rendering features I'd like to add in the future:

• Skyboxes
• Proper refraction
• Textures (Proper UVs for objects)
  • Normal maps
  • Reflectiveness maps
  • Roughness maps
• Ambient occlusion
• Global illumination (possibly)
• Caustics (possibly, an extremely tricky subject)
• A scene description method
  • Variables
  • Loops
  • Functions
  • User-defined functions

Progress

9/14/2021

Today, we decided that I would work on a raytracer in Rust. I began working on it. By the end of the day, it is capable of rendering spheres, planes, meshes (arbitrary wavefront OBJ models), reflections, sun lights, and can shade with Blinn-Phong shading. I parallelized it with the Rust library Rayon.

Below is a screenshot, 800x600, that renders in 0.022 seconds.

9/15/2021

Development was slower today because I have already implemented most features I would like to demo before I go further. I worked on optimization a bit, made my Rust code more idiomatic, and added point lights. Here is a screenshot, 1920x1080, that rendered in 0.102s.

9/16/2021

Along with a tiny bit of work last night, I added a feature my old raytracer did not have: textures. I went through each primitive I'd implemented so far and added a way for a ray hit to also return the UV coordinates of where to pull from its texture. For cubes, it's quite simple: each face just renders the image back out as it was. For meshes, however, it's a lot more complicated. Every triangle vertice holds an index that refers back to the texcoords list of UVs in the mesh itself. When a ray strikes a triangle, the barycentric UVs are calculated, and later are converted to be in the space of the image. This took an immense amount of trial and error. I had to try different permutations of UVW from barycentric coordinates (turns out the solution was WUV), and mess with a bunch of other random trial-and-error stuff like not inverting v to be in the space of the image (i.e. v should have been 1. - v when moving to image space).

Here is an image of a fedora mesh with a texture that I ripped from the game Roblox for testing's sake.

Later today, or at some point in the future, I'd like to work on adding normal maps (as well as maps for other physical properties), but this will require some more implementation details.

Here's another scene I threw together with 8 lights and 10 objects. It is 2560x1440, and took 6.961 seconds to render. Not bad, but not great.

9/20/2021

I took a break because I went home this weekend, but today I added skybox support, including support for cubemaps. Here's what the previous scene looks like with a cubemap I stole from Google Images:

10/3/2021

I haven't updated this in a while but since, I've added a number of extra textures, refraction, and most importantly, an implementation of a BVH that builds from top-down, making mesh renders extremely fast.

Here's a scene with one light, 4 objects, a semi-detailed mesh, and refraction + reflections to demonstrate. It is 1920x1080, and rendered in 0.1127 seconds.

10/4/2021

Today, I realized that scene construction when loading assets into memory is actually pretty slow, so I added a way to differentiate between scene construction time and render time, which is a very important thing to take into account for this scene in particular:

This image renders in 0.41624472s, but 0.3187096s of those are dedicated to scene construction. This includes loading assets into memory and processing them (decoding image files, reading OBJ files, etc.), but presumably almost all of it is loading and decoding the 3 MB cubemap into memory. This means this render actually took 0.09753512s, which is very fast at 1920x1080, with a mesh, refractions, and reflections.

Here's an image of the same scene from above:

10/6/2021

Today, I started working on the SDL tokenizer and AST. It can parse basic SDL files. At this point, it is capable of describing objects and their properties, but I would like to add some more imperative programming constructs like loops over a range to automatically construct circles.

As of now, the SDL looks something like this:

sphere {
  position: <0, 0, 0>,
  radius: 1,
  material: {
    color: <1, 0, 0>,
    reflectiveness: 0.3,
  },
}

aabb {
  position: <3, 3, 3>,
  size: <4, 2, 2>,
  material: {
    color: <0, 0.6, 1>,
  }
}

10/7/2021

At this point, the SDL is in a usable state. It can successfully describe and render the following scene:

# This is a test scene.

camera {
    # Render the image as 1920x1080.
    vw: 1920,
    vh: 1080,

    fov: 60,
    origin: <-3, 3, 0>,
    pitch: -0.5,
    yaw: 0.4,
}

# We just need one sun light.
sun {
    vector: <-0.8, -1, -0.3>,
    intensity: 0.8,
    specular_power: 64,
}

# This is the main UWL cube in the front.
aabb {
    position: vec(random(-1, 1), random(0, 1), random(-9, -7)),
    size: <1, 1, 1>,
    material: {
        texture: image("assets/uwl.png"),
    }
}

# This cube is reflective, to the right of the cube.
sphere {
    position: <2.5, 0, -5>,
    radius: 1,
    material: {
        texture: solid(color(200, 200, 200)),
        reflectiveness: 0.7,
    }
}

# This cube is solid opaque, to the left of the cube.
sphere {
    position: <-2.5, 0, -5>,
    radius: 1,
    material: {
        texture: solid(color(200, 200, 200)),
    }
}

# This is a wall behind all of the objects.
aabb {
    position: <0, 2, -12>,
    size: <10, 3, 1>,
}

# Finally, a checkered ground plate.
plane {
    origin: <0, -1, 0>,
    material: {
        texture: checkerboard(color(128, 128, 128), color(255, 255, 255)),
    }
}

point_light {
    position: <0, 0, -3.5>,
    color: color(255, 100, 100),
    intensity: 2,
}

The SDL is capable of functions like sin(x), cos(x), normalize(vector), add(vector, vector), mul(x, y), and so on. You can safely nest functions, add comments with #, add any number of objects, add image textures, and more. This is all done in the sdl crate.

10/19/2021

Today, I got scope stack and for loops working. The following code produces the following image:

tau = mul(pi(), 2)
segments = 16

sun {
    vector: <-0.8, -1, -0.2>,
}

for i in 0 to segments {
    frac = div(i, segments)
    inner = mul(frac, tau)
    color_channel = mul(frac, 255)

    sphere {
        position: vec(cos(inner), sin(inner), -4),
        radius: 0.3,
        material: {
            texture: solid(color(color_channel, color_channel, color_channel)),
        }
    }
}

10/20/2021

I have done a lot with the SDL today! I refined variables, added a Shunting-yard expression parser, streamlined the vector constructor, and added time parameterization to create GIFs. The SDL can now generate a sequence of PNGs, and then you can use a tool like FFmpeg to convert these to a coherent GIF. Here is a coherent GIF below generated from the adjacent code:

# Some variables for quick customization. We insert them into our camera...
let vw = 500
let vh = 500
let fov = 40
camera { vw, vh, fov, yaw: 0.0001, pitch: 0.0002 }

# Add a basic skybox.
skybox {
    type: "cubemap",
    image: "assets/space.png"
}

# Here are some variables defined in the top-level scope.
let dist = 3
let radius = 0.5
let n = 24
let time_scale = PI / 32

# Add a basic sun light...
sun {
    vector: <-0.8, -1, -0.2>,
    intensity: 0.8
}

# A for loop, over the range [0..n)
for i in 0 to n {
    # Add a sphere in each iteration...
    sphere {
        # With a position following a circle, with radius `dist`.
        position: <
            cos(i / n * TAU) * dist * cos(t * time_scale),
            sin(i / n * TAU) * dist,
            cos(i / n * TAU) * dist * sin(t * time_scale) - 12
        >,

        # Set the radius to our variable `radius`. Leaving out a value (e.g. `radius: 1`)
        # tries to pull a value out of a variable of the same name, in this case, one we set in the
        # top-level scope.
        radius,

        material: {
            # Use the HSV color constructor to pick colors off of a rainbow.
            texture: solid(hsv(i / n * 360, 1, 1)),
            reflectiveness: 0.2
        }
    }
}

# Finally one shiny sphere in the middle, because why not!
sphere {
    position: <0, 0, -13>,
    radius: 2,
    material: {
        reflectiveness: 0.8
    }
}

10/28/2021

Since my last progress update, I have added a number of features to the SDL, as well as a few rendering features. I've added area lights (with a shoddy implementation) as well as user-defined functions, comparison operators, logic operators, if/if-else/if-else-if/if-else-if-else statements, and probably more.

Here's an example of fizz-buzz implemented in the scene description language:

for n in 1 to 50 {
    if n % 3 == 0 && n % 5 == 0 {
        print("FizzBuzz")
    } else if n % 3 == 0 {
        print("Fizz")
    } else if n % 5 == 0 {
        print("Buzz")
    } else {
        print(n)
    }
}

11/8/2021

Today, I got a basic implementation of arrays working, as well as procedural mesh generation. Right now, things are very very slow, and internally arrays are not implemented very well. I would like to streamline this process and make the internals less fuzzy. Here's a sample image and the SDL code used to produce it.

let w = 48
let h = 48
let terrain = []

sun { vector: <-0.8, -1, -0.2> }

camera {
    origin: <0, 4, 0>,
    pitch: -0.5
}

for z in 0 to h {
    for x in 0 to w {
        terrain << perlin(x * 0.15, z * 0.15) * 2
    }
}

let verts = []
for z in 0 to h - 1 {
    for x in 0 to w - 1 {
        verts << <x, terrain[x + z * w], z>
        verts << <x, terrain[x + (z + 1) * w], z + 1>
        verts << <x + 1, terrain[x + 1 + z * w], z>

        verts << <x, terrain[x + (z + 1) * w], z + 1>
        verts << <x + 1, terrain[x + 1 + (z + 1) * w], z + 1>
        verts << <x + 1, terrain[x + 1 + z * w], z>
    }
}

mesh {
    verts,
    position: <0, -3, -20>,
    material: {
        texture: solid(rgb(0, 180, 0))
    }
}

11/14/2021

Today, I reworked arrays internally and now reference objects are much more satisfyingly implemented. They are cleaned up when they go out of scope, and the awkward << syntax has been replaced with push(array, value). Here's an example of nested arrays in action:

let a = []

for i in 0 to 4 {
    push(a, [])
    for j in 0 to 4 {
        push(a[i], j)
    }
}

for i in 0 to len(a) {
    for j in 0 to len(a[i]) {
        print(a[i][j])
    }
    print("")
}

11/22/2021

I wrote an icosphere generator, which takes an icosahedron and subdivides it, normalizing the vertices at the end, which allows you to create spheres with very even distributions of similarly sized triangles all around.

Then, I applied noise and added water to make this simple procedural planet generator:

This image is a bit older, but I have set up a Cornell box scene whose contents is very easy to switch out on the fly:

Here's a Cornell box with some icosahedrons inside to show you how fluidly both scenes can be combined:

One more bonus image with spheres randomly placed in space:

12/6/2021

It's been a while since I've worked on this project, but today I added a few features to the SDL while working on a procedural island generator, which uses simplex noise and fractal brownian motion:

Be sure to check out the source in scenes/island.sdl. I'd like to smooth these normals out soon!

12/13/2021

I have since internally worked the entire mesh system, and now support recalculating normals, smoothing normals of vertices that are shared by multiple triangles. Moreover, you can now specify normals for each vertex manually in the SDL if you wish.

Take a peek at this smoothened terrain that reflects into space!

And here's the island from last week, but smooth this time.