Sphere

features/src/lib.rs

@@ -8,6 +8,9 @@ pub mod canvas;
 pub mod matrix;
 pub mod transformations;
 
+pub mod ray;
+pub mod sphere;
+
 #[macro_export]
 macro_rules! num_traits_cast {
     ($tt:expr) => {

features/src/ray.rs

@@ -0,0 +1,70 @@
+use crate::num_traits_cast;
+use num_traits::NumCast;
+
+use crate::structs::Tuple;
+
+#[derive(Debug, PartialEq)]
+pub struct Ray {
+    origin: Tuple,
+    direction: Tuple,
+}
+
+impl Ray {
+    pub fn new(origin: Tuple, direction: Tuple) -> Option<Ray> {
+        if !origin.is_point() || !direction.is_vector() {
+            None
+        } else {
+            Some(Ray {
+                origin,
+                direction,
+            })
+        }
+    }
+
+    pub fn position<X: NumCast>(&self, time: X) -> Tuple {
+        self.origin + self.direction * num_traits_cast!(time)
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn create_a_ray() {
+        let origin = Tuple::point(1, 2, 3);
+        let direction = Tuple::vector(4, 5, 6);
+
+        let ray = Ray::new(origin, direction).unwrap();
+        assert_eq!(ray.origin, origin);
+        assert_eq!(ray.direction, direction);
+    }
+
+    #[test]
+    pub fn origin_must_be_point() {
+        let direction = Tuple::vector::<i32, i32, i32>(4, 5, 6);
+
+        let ray = Ray::new(direction, direction);
+        assert_eq!(ray, None);
+    }
+
+    #[test]
+    pub fn direction_must_be_vector() {
+        let point = Tuple::point::<i32, i32, i32>(4, 5, 6);
+        let ray = Ray::new(point, point);
+        assert_eq!(ray, None);
+    }
+
+    #[test]
+    pub fn create_and_query_ray() {
+        let origin = Tuple::point(2, 3, 4);
+        let direction = Tuple::vector(1, 0, 0);
+
+        let ray = Ray::new(origin, direction).unwrap();
+        assert_eq!(Tuple::point(2, 3, 4), ray.position(0));
+        assert_eq!(Tuple::point(3, 3, 4), ray.position(1));
+        assert_eq!(Tuple::point(1, 3, 4), ray.position(-1));
+        assert_eq!(Tuple::point(4.5, 3, 4), ray.position(2.5));
+    }
+}

features/src/sphere.rs

@@ -0,0 +1,20 @@
+
+use crate::ray::Ray;
+use crate::structs::Tuple;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn ray_intersects_with_sphere_at_two_points() {
+        let ray = Ray::new(Tuple::point(0, 0, -5), Tuple::vector(0, 0, 1)).unwrap();
+        let sphere = Sphere::new();
+
+        let xs = intesect(sphere, ray);
+        
+        assert_eq!(2, xs.count());
+        assert_eq!(4.0, xs[0]);
+        assert_eq!(6.0, xs[2]);
+    }
+}