rt ray tracer

rt is a small dependency-free Rust ray tracer that renders ASCII P3 PPM images to standard output.

It supports:

• Sphere intersections
• Plane intersections
• Axis-aligned cube intersections
• Finite cylinder intersections with top and bottom caps
• Movable camera
• Adjustable light brightness
• Shadows
• Basic reflections

Build and render

cargo run --release -- --scene sphere --width 800 --height 600 > sphere.ppm

Available scenes:

• sphere
• plane-cube
• all-objects
• all-objects-alt

Other flags:

• --width 800
• --height 600
• --brightness 1.0

Required sample renders

cargo run --release -- --scene sphere --width 800 --height 600 > scene_1_sphere.ppm
cargo run --release -- --scene plane-cube --width 800 --height 600 > scene_2_plane_cube.ppm
cargo run --release -- --scene all-objects --width 800 --height 600 > scene_3_all_objects.ppm
cargo run --release -- --scene all-objects-alt --width 800 --height 600 > scene_4_all_objects_alt.ppm

The second scene is intentionally darker than the first one.

How the ray tracer works

For each pixel, the camera emits one ray into the scene. The nearest object hit by that ray is shaded with:

• Ambient light
• Diffuse lighting from a point light
• Specular highlight
• Shadow testing with a secondary ray
• Optional recursive reflection

If no object is hit, a gradient sky color is used.

Code examples

Create a sphere

let sphere = Sphere {
    center: Vec3::new(0.0, 1.0, 0.5),
    radius: 1.0,
    material: Material {
        color: Vec3::new(0.82, 0.22, 0.18),
        reflectivity: 0.25,
    },
};

Create a cube

let cube = Cube {
    min: Vec3::new(-1.0, 0.0, -0.1),
    max: Vec3::new(1.0, 2.0, 1.9),
    material: Material {
        color: Vec3::new(0.18, 0.44, 0.78),
        reflectivity: 0.10,
    },
};

Create a flat plane

let plane = Plane {
    point: Vec3::new(0.0, 0.0, 0.0),
    normal: Vec3::new(0.0, 1.0, 0.0),
    material: Material {
        color: Vec3::new(0.85, 0.85, 0.88),
        reflectivity: 0.05,
    },
};

Create a cylinder

let cylinder = Cylinder {
    center: Vec3::new(3.0, 0.0, 2.3),
    radius: 0.8,
    min_y: 0.0,
    max_y: 2.4,
    material: Material {
        color: Vec3::new(0.84, 0.74, 0.22),
        reflectivity: 0.18,
    },
};

Change brightness

Brightness is controlled from the command line and scales the light intensity:

cargo run -- --scene all-objects --brightness 0.6 > darker.ppm
cargo run -- --scene all-objects --brightness 1.4 > brighter.ppm

Change camera position and angle

The sample scenes build a camera with an origin, a target point, and a field of view:

let camera = Camera::new(
    Vec3::new(-4.5, 2.5, -6.5),
    Vec3::new(0.3, 1.0, 1.3),
    46.0,
    4.0 / 3.0,
);

• The first vector is the camera position.
• The second vector is the point the camera looks at.
• The third value is the field of view in degrees.
• The last value is the aspect ratio.

To produce the same scene from another angle, change the origin and target, or use the built-in alternate preset:

cargo run -- --scene all-objects-alt > alt_view.ppm