Sphere

features/src/lib.rs

@@ -7,7 +7,9 @@ pub mod color;
 pub mod canvas;
 pub mod matrix;
 pub mod transformations;
+
 pub mod ray;
+pub mod sphere;
 
 #[macro_export]
 macro_rules! num_traits_cast {

features/src/ray.rs

@@ -1,13 +1,16 @@
+use crate::num_traits_cast;
+use num_traits::NumCast;
+
 use crate::structs::Tuple;
 
 #[derive(Debug, PartialEq)]
-struct Ray {
+pub struct Ray {
     origin: Tuple,
     direction: Tuple,
 }
 
 impl Ray {
-    fn new(origin: Tuple, direction: Tuple) -> Option<Ray> {
+    pub fn new(origin: Tuple, direction: Tuple) -> Option<Ray> {
         if !origin.is_point() || !direction.is_vector() {
             None
         } else {
@@ -17,6 +20,10 @@ impl Ray {
             })
         }
     }
+
+    pub fn position<X: NumCast>(&self, time: X) -> Tuple {
+        self.origin + self.direction * num_traits_cast!(time)
+    }
 }
 
 
@@ -49,4 +56,15 @@ mod tests {
         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]);
+    }
+}