diff --git a/src/main.rs b/src/main.rs
index 6c6428b..0e3ee25 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -9,7 +9,7 @@ use render::{World,Camera};
 use vec3::{Point3,Vec3};
 
 use material::{Metal,Lambertian,Material};
-
+use std::sync::Arc;
 
 
 fn main() {
@@ -21,21 +21,17 @@ fn main() {
 
 
     let m = Lambertian::new(Vec3::new(0.5,0.5,0.5));
-    let b: Box <dyn Material> = Box::new(m);
-    let world_m = std::rc::Rc::new(b);
+    let world_m: Arc <dyn Material> = Arc::new(m);
 
     let m = Lambertian::new(Vec3::new(0.1, 0.2, 0.5));
-    let b: Box <dyn Material> = Box::new(m);
-    let center_m = std::rc::Rc::new(b);
+    let center_m: Arc <dyn Material> = Arc::new(m);
 
     let m = Metal::new(Vec3::new(0.8, 0.8, 0.8), 0.3);
-    let b: Box <dyn Material> = Box::new(m);
-    let left_m = std::rc::Rc::new(b);
+    let left_m: Arc <dyn Material> = Arc::new(m);
 
 
     let m = Metal::new(Vec3::new(0.8, 0.6, 0.2), 0.5);
-    let b: Box <dyn Material> = Box::new(m);
-    let right_m = std::rc::Rc::new(b);
+    let right_m: Arc <dyn Material> = Arc::new(m);
 
     let mut camera = Camera::new(aspect_ratio,image_width,focal_length,viewport_height,camera_center);
     let mut world = World::new();
diff --git a/src/object.rs b/src/object.rs
index b3c5852..c465e72 100644
--- a/src/object.rs
+++ b/src/object.rs
@@ -2,6 +2,7 @@ use crate::vec3::{Point3, Ray, Vec3, Interval};
 use crate::material::{Material,Scatter};
 
 use rand::prelude::*;
+use std::sync::Arc;
 
 
 pub trait Hittable {
@@ -13,7 +14,7 @@ pub struct HitRecord {
     normal: Vec3,
     root: f64,
     front_face: bool,
-    material: std::rc::Rc<Box<dyn Material>>,
+    material: Arc<dyn Material>,
 }
 
 impl HitRecord {
@@ -43,11 +44,11 @@ impl HitRecord {
 pub struct Sphere {
     radius: f64,
     center: Point3,
-    material: std::rc::Rc<Box<dyn Material>>
+    material: Arc<dyn Material>
 }
 
 impl Sphere {
-    pub fn new(radius: f64, center: Point3, material:std::rc::Rc<Box<dyn Material>>) -> Self {
+    pub fn new(radius: f64, center: Point3, material: Arc<dyn Material>) -> Self {
         Sphere { radius, center , material}
     }
 }
diff --git a/src/render.rs b/src/render.rs
index c28d22c..a13581f 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -1,11 +1,12 @@
 use crate::object::{HitRecord, Hittable};
 use crate::vec3::{Interval, Ray, Vec3, Point3};
 use crate::image::Image;
+use std::sync::Arc;
 
 use rand::prelude::*;
 
 pub struct World {
-    pub objects: Vec<Box<dyn Hittable>>,
+    pub objects: Vec<Arc<dyn Hittable>>,
 }
 
 impl World {
@@ -16,7 +17,7 @@ impl World {
     }
 
     pub fn add(&mut self, object: impl Hittable + 'static) {
-	self.objects.push(Box::new(object));
+	self.objects.push(Arc::new(object));
     }
 
     pub fn hit(&self, ray: Ray, interval:Interval) -> Option<HitRecord> {