Renderer/src/main.rs

mod vec3;
mod color;
mod ray;
use vec3::Vec3;
use vec3::Color;
use vec3::Point3;
use ray::Ray;
use std::env;
use std::fs::File;
use std::io::BufWriter;
use std::io::Write;

fn hit_sphere(center: &Point3, radius: f64, r: &Ray) -> f64 {
    let oc = r.origin() - *center;
    let a = Vec3::dot(r.direction(), r.direction());
    let b = 2.0 * Vec3::dot(oc, r.direction());
    let c = Vec3::dot(oc, oc) - radius*radius;
    let discriminant = b*b - 4.0*a*c;

    if discriminant < 0.0 {
        return -1.0;
    } else {
        return (-b - discriminant.sqrt()) / (2.0*a);
    }
}

fn ray_color(r: &Ray) -> Color{
    let t = hit_sphere(&Point3::new(0.0, 0.0, -1.0), 0.5, r);
    if t > 0.0 {
        let n = Vec3::unit_vector(r.at(t) - Vec3::new(0.0, 0.0, -1.0));
        return 0.5*Color::new(n.x()+1.0, n.y()+1.0, n.z()+1.0);
    }
    
    let unit_direction = r.direction();
    let t = 0.5*(unit_direction.y() + 1.0);
    return (1.0-t)*Color::new(1.0,1.0,1.0) + t*Color::new(0.5,0.7,1.0);
}

fn main() {

    // File
    let mut default_file = "image.ppm";

    // Image
    let aspect_ratio = 16.0 / 9.0;
    let image_width = 800;
    let image_height = (image_width as f64 / aspect_ratio) as u64;

    // Camera
    let viewport_height = 2.0;
    let viewport_width = aspect_ratio * viewport_height;
    let focal_length = 1.0;

    let origin = Point3::new(0.0,0.0,0.0);
    let horizontal = Vec3::new(viewport_width, 0.0, 0.0);
    let vertical = Vec3::new(0.0, viewport_height, 0.0);
    let lower_left_corner = origin - horizontal/2.0 - vertical/2.0 - Vec3::new(0.0, 0.0, focal_length);
    
    // Render
    let args: Vec<String> = env::args().collect();
    if args.len() > 1 && args[1] != "" {
        default_file = &args[1];
    }
    let mut file = BufWriter::new(File::create(default_file).unwrap());
    writeln!(&mut file,"P3\n{image_width} {image_height}\n255\n").unwrap();

    for j in (0..image_height).rev() {
        eprint!("\rScanlines remaining: {j:5}");
        for i in 0..image_width {
            let u = i as f64 / (image_width-1) as f64;
            let v = j as f64 / (image_height-1) as f64;
            let r = Ray::new(origin, lower_left_corner + u*horizontal + v*vertical - origin);
            let pixel_color = ray_color(&r);

            color::write_color(&mut file, pixel_color);
        }
    }
    eprintln!("\nDone!");
}