diff --git a/Object.h b/Object.h
index f3cd7c8..c89dd63 100644
--- a/Object.h
+++ b/Object.h
@@ -1,7 +1,26 @@
 #pragma once
 #include "Vector3.h"
 class Material;
-class Object {
+class LinkedList {
+public:
+	LinkedList* mNext;
+	LinkedList() {
+		mNext = nullptr;
+	}
+	template<typename T>
+	T* Next() {
+		return (T*)mNext;
+	}
+	void Append(LinkedList* node) {
+		if (mNext == nullptr) {
+			mNext = node;
+		}
+		else {
+			mNext->Append(node);
+		}
+	}
+};
+class Object : public LinkedList{
 public:
 	Geometry *mGeometry;
 	Material *mMaterial;
diff --git a/Scene.cpp b/Scene.cpp
index f749aba..ea2169a 100644
--- a/Scene.cpp
+++ b/Scene.cpp
@@ -10,16 +10,17 @@
 static int sTotalPixelCount = 0;
 static int sViewportWidth = 0, sViewportHeight = 0;
 static Camera* sCamera = nullptr;
-Sphere sphere(Vector3(0.0f, 0.0f, -5.0f), 0.5f);
+Sphere sphere(Vector3(0.0f, 0.5f, 0.0f), 0.5f);
 static Object* sRootObject = nullptr;
 static Material* lambert = nullptr;
 static int sSampleCount = 64;
+static int sMaxBounceTime = 30;
 void AddObject(Object* object) {
 	if (sRootObject == nullptr) {
 		sRootObject = object;
 	}
 	else {
-		//TODO
+		sRootObject->Append(object);
 	}
 }
 void Init(int width, int height)
@@ -28,7 +29,9 @@ void Init(int width, int height)
 	sViewportWidth = width;
 	sViewportHeight = height;
 	sCamera = new Camera(45.0f, float(width) / float(height));
-	sCamera->LookAt(Vector3(0.0f, 0.0f, 0.0f), Vector3(0.0f, 0.0f, -1.0f), Vector3(0.0f, 1.0f, 0.0f));
+	sCamera->LookAt(Vector3(3.0f, 1.0f, 3.0f), Vector3(0.0f, 0.0f, 0.0f), Vector3(0.0f, 1.0f, 0.0f));
+	Material* earth_material = new LamberMaterial(Vector3(0.5f, 0.3f, 0.1f));
+	AddObject(new Object(new Sphere(Vector3(0.0f, -1000.0f, 0.0), 1000.0f), earth_material));
 	lambert = new LamberMaterial(Vector3(0.1f, 0.4f, 0.7f));
 	AddObject(new Object(&sphere, lambert));
 }
@@ -50,16 +53,28 @@ Vector3 GetEnviromentColor(const Ray& input_ray) {
 	return factor * top_color + (1.0f - factor) * bottom_color;
 }
 
-Vector3 GetColor(const Ray& input_ray) {
+Vector3 RenderOneSample(const Ray& input_ray, int bounce_time) {
 	HitPoint hit_point;
-	if (sRootObject->HitTest(input_ray, 0.01f, 100.0f, hit_point)) {
-		Ray scatter_ray;
-		if (hit_point.mMaterial->Scatter(input_ray, hit_point, scatter_ray)) {
-			return GetColor(scatter_ray);
+	float max_distance = 1000.0f;
+	Object* current_object = sRootObject;
+	Object* hitted_object = nullptr;
+
+	while (current_object != nullptr) {
+		if (current_object->HitTest(input_ray, 0.01f, max_distance, hit_point)) {
+			max_distance = hit_point.mDistance;
+			hitted_object = current_object;
 		}
+		current_object = current_object->Next<Object>();
 	}
-
-	return GetEnviromentColor(input_ray);
+	if (hitted_object != nullptr) {
+		if(bounce_time < sMaxBounceTime){
+			Ray scatter_ray;
+			if (hit_point.mMaterial->Scatter(input_ray, hit_point, scatter_ray)) {
+				return RenderOneSample(scatter_ray, bounce_time + 1);
+			}
+		}
+	}
+	return GetEnviromentColor(input_ray) * input_ray.mLightAttenuation;
 }
 
 void RenderOnePixel(int pixel_index) {
@@ -73,7 +88,7 @@ void RenderOnePixel(int pixel_index) {
 		float u = (float(x) + offset_u) / sViewportWidth;
 		float v = (float(y) + offset_v) / sViewportHeight;
 		Ray ray = sCamera->GetRay(u, v);
-		Vector3 current_color = GetColor(ray);
+		Vector3 current_color = RenderOneSample(ray,0);
 		color = color + current_color;
 	}
 	color /= sSampleCount;
diff --git a/Sphere.cpp b/Sphere.cpp
index 5507489..bb01341 100644
--- a/Sphere.cpp
+++ b/Sphere.cpp
@@ -23,17 +23,19 @@ bool Sphere::HitTest(const Ray& input_ray, float min_distance, float max_distanc
 	bool isHited = false;
 	float distance = -1.0f;
 	if (determinant > 0.0f) {
-		distance = (-b - sqrtf(determinant))/ 2.0f;
+		distance = (-b - sqrtf(determinant))/ 2.0f *a;
 		if (distance > min_distance && distance < max_distance) {
 			isHited = true;
 		}
-		distance = (-b + sqrtf(determinant)) / 2.0f;
-		if (distance > min_distance && distance < max_distance) {
-			isHited = true;
+		else {
+			distance = (-b + sqrtf(determinant)) / 2.0f*a;
+			if (distance > min_distance && distance < max_distance) {
+				isHited = true;
+			}
 		}
 	}
 	else if (determinant == 0.0f) {
-		distance = -b / 2.0f;
+		distance = -b / (2.0f * a);
 		if (distance > min_distance && distance < max_distance) {
 			isHited = true;
 		}