camera: implement Camera::render.

rtchallenge/src/camera.rs

@@ -1,4 +1,4 @@
-use crate::{matrices::Matrix4x4, rays::Ray, tuples::Tuple};
+use crate::{canvas::Canvas, matrices::Matrix4x4, rays::Ray, tuples::Tuple, world::World, BLACK};
 
 pub struct Camera {
     hsize: usize,
@@ -121,4 +121,39 @@ impl Camera {
 
         Ray::new(origin, direction)
     }
+
+    /// Use camera to render an image of the given world.
+    ///
+    /// # Examples
+    /// ```
+    /// use std::f32::consts::PI;
+    ///
+    /// use rtchallenge::{
+    ///     camera::Camera,
+    ///     transformations::view_transform,
+    ///     tuples::{Color, Tuple},
+    ///     world::World,
+    /// };
+    ///
+    /// // Rendering a world with a camera.
+    /// let w = World::test_world();
+    /// let mut c = Camera::new(11, 11, PI / 2.);
+    /// let from = Tuple::point(0., 0., -5.);
+    /// let to = Tuple::point(0., 0., 0.);
+    /// let up = Tuple::vector(0., 1., 0.);
+    /// c.transform = view_transform(from, to, up);
+    /// let image = c.render(&w);
+    /// assert_eq!(image.get(5, 5), Color::new(0.38066, 0.47583, 0.2855));
+    /// ```
+    pub fn render(&self, w: &World) -> Canvas {
+        let mut image = Canvas::new(self.hsize, self.vsize, BLACK);
+        for y in 0..self.hsize {
+            for x in 0..self.vsize {
+                let ray = self.ray_for_pixel(x, y);
+                let color = w.color_at(&ray);
+                image.set(x, y, color);
+            }
+        }
+        image
+    }
 }