diff --git a/Camera.cpp b/Camera.cpp
index 3fe35a6..b29257c 100644
--- a/Camera.cpp
+++ b/Camera.cpp
@@ -24,7 +24,7 @@ void Camera::LookAt(const Vector3& position, const Vector3& center, const Vector
 	mUVector = right_direction;
 	mVVector = up_direction;
 	mUSpanVector = mNearPlaneWidth * mUVector;
-	mVSpanVector = mNearPlaneHeight * mUVector;
+	mVSpanVector = mNearPlaneHeight * mVVector;
 	mCenter = center;
 	mPosition = position;
 	mUp = up;
diff --git a/Ray.cpp b/Ray.cpp
index 75e4024..e7c523c 100644
--- a/Ray.cpp
+++ b/Ray.cpp
@@ -8,6 +8,6 @@ void Ray::Set(const Vector3& origin, const Vector3& direction, const Vector3& at
 	mDirection.Normalize();
 	mLightAttenuation = attenuation;
 }
-Vector3 Ray::PointAt(float k) {
+Vector3 Ray::PointAt(float k) const {
 	return mOrigin + k * mDirection;
 }
\ No newline at end of file
diff --git a/Ray.h b/Ray.h
index 48352f1..674e901 100644
--- a/Ray.h
+++ b/Ray.h
@@ -5,5 +5,5 @@ public:
 	Vector3 mOrigin, mDirection, mLightAttenuation;
 	Ray(const Vector3& origin, const Vector3& direction, const Vector3& attenuation);
 	void Set(const Vector3& origin, const Vector3& direction, const Vector3& attenuation);
-	Vector3 PointAt(float k);
+	Vector3 PointAt(float k) const;
 };
\ No newline at end of file
diff --git a/Scene.cpp b/Scene.cpp
index b24e167..e06c5b3 100644
--- a/Scene.cpp
+++ b/Scene.cpp
@@ -2,17 +2,20 @@
 #include "util.h"
 #include "Camera.h"
 #include "Ray.h"
+#include "Vector3.h"
+#include "Sphere.h"
 #pragma comment(lib, "winmm.lib")
 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);
 void Init(int width, int height)
 {
 	sTotalPixelCount = width * height;
 	sViewportWidth = width;
 	sViewportHeight = height;
 	sCamera = new Camera(45.0f, float(width) / float(height));
-	sCamera->LookAt(Vector3(0.0f,0.0f,1.0f), Vector3(0.0f,0.0f,0.0f), Vector3(0.0f,1.0f,0.0f));
+	sCamera->LookAt(Vector3(0.0f, 0.0f, 0.0f), Vector3(0.0f, 0.0f, -1.0f), Vector3(0.0f, 1.0f, 0.0f));
 }
 
 float GetEscaptedTime() {
@@ -31,13 +34,25 @@ void RenderOnePixel(int pixel_index) {
 	float u = float(x) / sViewportWidth;
 	float v = float(y) / sViewportHeight;
 	Ray ray = sCamera->GetRay(u,v);
-	float rf = ray.mDirection.x > 0.0f ? ray.mDirection.x : -ray.mDirection.x;
-	float gf = ray.mDirection.y > 0.0f ? ray.mDirection.y : -ray.mDirection.y;
-	float bf = ray.mDirection.z > 0.0f ? ray.mDirection.z : -ray.mDirection.z;
-	AByte r = AByte( rf * 255.0f);
-	AByte g = AByte( gf * 255.0f);
-	AByte b = AByte( bf * 255.0f);
-	SetColor(x, y, r, g, b, 255);
+	HitPoint hit_point;
+	if (sphere.HitTest(ray, 0.0f, 100.0f, hit_point)) {
+		float rf = hit_point.mNormal.x * 0.5f + 0.5f;
+		float gf = hit_point.mNormal.y * 0.5f + 0.5f;
+		float bf = hit_point.mNormal.z * 0.5f + 0.5f;
+		AByte r = AByte(rf * 255.0f);
+		AByte g = AByte(gf * 255.0f);
+		AByte b = AByte(bf * 255.0f);
+		SetColor(x, y, r, g, b, 255);
+	}
+	else {
+		float rf = ray.mDirection.x > 0.0f ? ray.mDirection.x : -ray.mDirection.x;
+		float gf = ray.mDirection.y > 0.0f ? ray.mDirection.y : -ray.mDirection.y;
+		float bf = ray.mDirection.z > 0.0f ? ray.mDirection.z : -ray.mDirection.z;
+		AByte r = AByte(rf * 255.0f);
+		AByte g = AByte(gf * 255.0f);
+		AByte b = AByte(bf * 255.0f);
+		SetColor(x, y, r, g, b, 255);
+	}
 }
 
 void Render()
diff --git a/Sphere.cpp b/Sphere.cpp
new file mode 100644
index 0000000..5507489
--- /dev/null
+++ b/Sphere.cpp
@@ -0,0 +1,51 @@
+#include "Sphere.h"
+#include"Ray.h"
+#include<math.h>
+
+Sphere::Sphere(const Vector3 & origin, float radius) {
+	mOrigin = origin;
+	mRadius = radius;
+}
+
+void Sphere::set(const Vector3 & origin, float radius)
+{
+	mOrigin = origin;
+	mRadius = radius;
+}
+
+bool Sphere::HitTest(const Ray& input_ray, float min_distance, float max_distance, HitPoint& hit_point) {
+	Vector3 sphere_center_to_ray = input_ray.mOrigin - mOrigin;
+	float a = Dot(input_ray.mDirection, input_ray.mDirection);
+	float b = 2.0f * Dot(sphere_center_to_ray, input_ray.mDirection);
+	float c = Dot(sphere_center_to_ray, sphere_center_to_ray) - mRadius * mRadius;
+	float determinant = b * b - 4.0f * a * c;
+
+	bool isHited = false;
+	float distance = -1.0f;
+	if (determinant > 0.0f) {
+		distance = (-b - sqrtf(determinant))/ 2.0f;
+		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 if (determinant == 0.0f) {
+		distance = -b / 2.0f;
+		if (distance > min_distance && distance < max_distance) {
+			isHited = true;
+		}
+	}
+
+	if (isHited) {
+		hit_point.mPosition = input_ray.PointAt(distance);
+		Vector3 normal = hit_point.mPosition - mOrigin;
+		normal.Normalize();
+		hit_point.mDistance = distance;
+		hit_point.mNormal = normal;
+	}
+
+	return isHited;
+}
diff --git a/Sphere.h b/Sphere.h
new file mode 100644
index 0000000..16f938e
--- /dev/null
+++ b/Sphere.h
@@ -0,0 +1,10 @@
+#pragma once
+#include "Vector3.h"
+class Sphere : public Geometry {
+public:
+	Vector3 mOrigin;
+	float mRadius;
+	Sphere(const Vector3& origin, float radius);
+	void set(const Vector3& origin, float radius);
+	bool HitTest(const Ray& input_ray, float min_distance, float max_distance, HitPoint& hit_point);
+};
diff --git a/Vector3.h b/Vector3.h
index e687c8f..cca27cb 100644
--- a/Vector3.h
+++ b/Vector3.h
@@ -37,4 +37,15 @@ public:
 };
 Vector3 operator*(float f, const Vector3& v);
 float Dot(const Vector3& l, const Vector3& r);
-Vector3 Cross(const Vector3& l, const Vector3& r);
\ No newline at end of file
+Vector3 Cross(const Vector3& l, const Vector3& r);
+class Material;
+struct HitPoint {
+	Vector3 mPosition;
+	Vector3 mNormal;
+	float mDistance;
+	Material* mMaterial;
+};
+class Ray;
+class Geometry {
+	virtual bool HitTest(const Ray& input_ray, float min_distance, float max_distance, HitPoint& hit_point) = 0;
+};
\ No newline at end of file
diff --git a/raytracing.vcxproj b/raytracing.vcxproj
index ed07c41..a5e4c56 100644
--- a/raytracing.vcxproj
+++ b/raytracing.vcxproj
@@ -130,6 +130,7 @@
     <ClCompile Include="main.cpp" />
     <ClCompile Include="Ray.cpp" />
     <ClCompile Include="Scene.cpp" />
+    <ClCompile Include="Sphere.cpp" />
     <ClCompile Include="util.cpp" />
     <ClCompile Include="Vector3.cpp" />
   </ItemGroup>
@@ -137,6 +138,7 @@
     <ClInclude Include="Camera.h" />
     <ClInclude Include="Ray.h" />
     <ClInclude Include="Scene.h" />
+    <ClInclude Include="Sphere.h" />
     <ClInclude Include="util.h" />
     <ClInclude Include="Vector3.h" />
   </ItemGroup>
diff --git a/raytracing.vcxproj.filters b/raytracing.vcxproj.filters
index 8dedff8..07d1d8c 100644
--- a/raytracing.vcxproj.filters
+++ b/raytracing.vcxproj.filters
@@ -33,6 +33,9 @@
     <ClCompile Include="Camera.cpp">
       <Filter>源文件</Filter>
     </ClCompile>
+    <ClCompile Include="Sphere.cpp">
+      <Filter>源文件</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="Scene.h">
@@ -50,5 +53,8 @@
     <ClInclude Include="Camera.h">
       <Filter>源文件</Filter>
     </ClInclude>
+    <ClInclude Include="Sphere.h">
+      <Filter>源文件</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file