eoc5: implement suggestiong at end of chapter 5.

rtchallenge/examples/eoc5.rs

@@ -0,0 +1,41 @@
+use core::f32;
+
+use anyhow::Result;
+
+use rtchallenge::{
+    canvas::Canvas,
+    rays::Ray,
+    spheres::{intersect, Sphere},
+    tuples::{Color, Tuple},
+};
+
+fn main() -> Result<()> {
+    let w = 200;
+    let h = w;
+    let mut c = Canvas::new(w, h);
+    let ray_origin = Tuple::point(0., 0., -5.);
+    let wall_z = 10.;
+    let wall_size = 7.;
+    let pixel_size = wall_size / w as f32;
+    let half = wall_size / 2.;
+    let color = Color::new(1., 0., 0.);
+    let shape = Sphere::default();
+
+    for y in 0..h {
+        let world_y = half - pixel_size * y as f32;
+        for x in 0..w {
+            let world_x = -half + pixel_size * x as f32;
+            let position = Tuple::point(world_x, world_y, wall_z);
+            let r = Ray::new(ray_origin, (position - ray_origin).normalize());
+            let xs = intersect(&shape, &r);
+            if xs.hit().is_some() {
+                c.set(x, y, color);
+            }
+        }
+    }
+
+    let path = "/tmp/eoc5.png";
+    println!("saving output to {}", path);
+    c.write_to_file(path)?;
+    Ok(())
+}