Always in-progress renderer.

It is copied to an appropriately named render as chapters are
implemented.

rtiow/src/bin/tracer.rs

@@ -0,0 +1,53 @@
+extern crate rand;
+extern crate rtiow;
+
+use rand::Rng;
+
+use rtiow::camera::Camera;
+use rtiow::hitable::Hit;
+use rtiow::hitable_list::HitableList;
+use rtiow::ray::Ray;
+use rtiow::sphere::Sphere;
+use rtiow::vec3::Vec3;
+
+fn color(r: Ray, world: &Hit) -> Vec3 {
+    if let Some(rec) = world.hit(r, 0., std::f32::MAX) {
+        return (rec.normal + 1.) * 0.5;
+    }
+
+    // No hit, choose color from background.
+    let unit_direction = r.direction().unit_vector();
+    let t = 0.5 * (unit_direction.y + 1.);
+    Vec3::new(1., 1., 1.) * (1. - t) + Vec3::new(0.5, 0.7, 1.) * t
+}
+
+fn main() -> Result<(), std::io::Error> {
+    let mut rng = rand::thread_rng();
+    let nx = 200;
+    let ny = 100;
+    let ns = 100;
+    println!("P3\n{} {}\n255", nx, ny);
+    let objects = vec![
+        Sphere::new(Vec3::new(0., 0., -1.), 0.5),
+        Sphere::new(Vec3::new(0., -100.5, -1.), 100.),
+    ];
+    let cam = Camera::new2x1();
+    let world = HitableList::new(objects.iter().map(|o| o).collect());
+    for j in (0..ny).rev() {
+        for i in 0..nx {
+            let mut col: Vec3 = Default::default();
+            for _ in 0..ns {
+                let u = (rng.gen_range::<f32>(0., 1.) + i as f32) / nx as f32;
+                let v = (rng.gen_range::<f32>(0., 1.) + j as f32) / ny as f32;
+                let r = cam.get_ray(u, v);
+                col = col + color(r, &world);
+            }
+            col = col / ns as f32;
+            let ir = (255.99 * col[0]) as u32;
+            let ig = (255.99 * col[1]) as u32;
+            let ib = (255.99 * col[2]) as u32;
+            println!("{} {} {}", ir, ig, ib);
+        }
+    }
+    Ok(())
+}