ft: 4: ray class + simpl gradient

src/ray.rs

@@ -0,0 +1,27 @@
+use crate::vec3::Vec3;
+
+pub struct Ray {
+    origin: Vec3,
+    dir: Vec3,
+}
+
+impl Ray {
+    pub fn at(self, t: f32) -> Vec3 {
+        self.origin + t * self.dir
+    }
+
+    pub fn new(origin: Vec3, dir: Vec3) -> Ray {
+        Ray {
+            origin: origin,
+            dir: dir,
+        }
+    }
+
+    pub fn origin(&self) -> &Vec3 {
+        &self.origin
+    }
+
+    pub fn dir(&self) -> &Vec3 {
+        &self.dir
+    }
+}