diff --git a/brdf/glass.cpp b/brdf/glass.cpp
index 45db1d96..88bf032a 100644
--- a/brdf/glass.cpp
+++ b/brdf/glass.cpp
@@ -29,7 +29,8 @@ Color Glass::sample_f(const Vector3 &wo, Vector3 &wi, float &pdf) const
     // Vector3 inputVector = Vector3(wo.x, wo.y, -wo.z);
     Vector3 inputVector = -wo;
     bool totalReflect;
-    wi = inputVector._refract(normal, etaInputSide, etaOutputSide, totalReflect);
+    float fresnel;
+    wi = inputVector._refract(normal, etaInputSide, etaOutputSide, totalReflect, fresnel);
 
     pdf = 1;
 
diff --git a/camera/camera.cpp b/camera/camera.cpp
index e7b087da..dc2b457b 100644
--- a/camera/camera.cpp
+++ b/camera/camera.cpp
@@ -6,7 +6,7 @@
 
 Camera::Camera()
 {
-    m_factor = 3;
+    m_factor = 2;
 
     m_Width = Common::default_screen_width * m_factor;
     m_Height = Common::default_screen_height * m_factor;
diff --git a/material/mixMaterial.cpp b/material/mixMaterial.cpp
index e0cb7df0..e3ee2346 100644
--- a/material/mixMaterial.cpp
+++ b/material/mixMaterial.cpp
@@ -33,18 +33,12 @@ Color MixMaterial::eval(float u, float v, const Vector3 &wo, Vector3 &wi, float
 
     bool totalReflect = false;
     Vector3 inputVector = -wo;
-    Vector3 refractVector = inputVector.refract(normal, etaOutside, etaInside, totalReflect);
+    float fresnel;
+    Vector3 refractVector = inputVector._refract(normal, etaOutside, etaInside, totalReflect, fresnel);
     float F = 1;
     if (!totalReflect)
     {
-        float sinOut = std::sqrt(1 - cosOut * cosOut);
-        float sinIn = sinOut * etaOutside / etaInside;
-        float cosIn = std::sqrt(1 - sinIn * sinIn);
-
-        float r_pa = (etaInside * cosOut - etaOutside * cosIn) / (etaInside * cosOut + etaOutside * cosIn);
-        float r_per = (etaOutside * cosOut - etaInside * cosIn) / (etaOutside * cosOut + etaInside * cosIn);
-
-        F = 0.5 * (r_pa * r_pa + r_per * r_per);
+        F = fresnel;
     }
 
     float rnd = Common::genRandomDecimal();
@@ -53,12 +47,12 @@ Color MixMaterial::eval(float u, float v, const Vector3 &wo, Vector3 &wi, float
 
     if (rnd < F)
     {
-        color = m_pMirrorBrdf->sample_f(wo, wi, pdf) * F;
+        color = m_pMirrorBrdf->sample_f(wo, wi, pdf);
         pdf = F;
     }
     else
     {
-        color = m_pGlassBrdf->sample_f(wo, wi, pdf) * (1 - F);
+        color = m_pGlassBrdf->sample_f(wo, wi, pdf);
         pdf = 1 - F;
     }
 
diff --git a/mathmatic/vector.cpp b/mathmatic/vector.cpp
index b974cc3f..9f0ea74a 100644
--- a/mathmatic/vector.cpp
+++ b/mathmatic/vector.cpp
@@ -184,7 +184,11 @@ Vector3 Vector3::reflect(const Vector3 &normal) const
     return 2 * m * n + (*this);
 }
 
-Vector3 Vector3::_refract(const Vector3 &normal, float etaInputSide, float etaOutputSide, bool &totalReflect) const
+Vector3 Vector3::_refract(const Vector3 &normal,
+                          float etaInputSide,
+                          float etaOutputSide,
+                          bool &totalReflect,
+                          float &fresnel) const
 {
     assert((normal != Vector3::ZERO && "Vector3::_refract"));
     assert((etaInputSide != 0) && "Vector3::_refract");
@@ -206,6 +210,7 @@ Vector3 Vector3::_refract(const Vector3 &normal, float etaInputSide, float etaOu
     if(sin_theta_out_sqr >= 1)
     {
         totalReflect = true;
+        fresnel = 1;
         return reflect(normal);
     }
 
@@ -224,6 +229,15 @@ Vector3 Vector3::_refract(const Vector3 &normal, float etaInputSide, float etaOu
 
     Vector3 out = out_p + out_n;
 
+    float cos_theta_in = dot;
+
+    float r_pa = (etaOutputSide * cos_theta_in - etaInputSide * cos_theta_out) /
+                 (etaOutputSide * cos_theta_in + etaInputSide * cos_theta_out);
+    float r_per = (etaInputSide * cos_theta_in - etaOutputSide * cos_theta_out) /
+                  (etaInputSide * cos_theta_in + etaOutputSide * cos_theta_out);
+
+    fresnel = 0.5 * (r_pa * r_pa + r_per * r_per);
+
     return out;
 }
 
diff --git a/mathmatic/vector.h b/mathmatic/vector.h
index e011fe79..73f08184 100644
--- a/mathmatic/vector.h
+++ b/mathmatic/vector.h
@@ -38,7 +38,11 @@ class Vector3
 
     Vector3 reflect(const Vector3 &normal) const;
     Vector3 refract(const Vector3 &normal, float etaInputSide, float etaOutputSide, bool &totalReflect) const;
-    Vector3 _refract(const Vector3 &normal, float etaOutside, float etaInside, bool &totalReflect) const;
+    Vector3 _refract(const Vector3 &normal,
+                     float etaOutside,
+                     float etaInside,
+                     bool &totalReflect,
+                     float &fresnel) const;
     bool isInSameSide(const Vector3 &that) const;
 
     static Vector3 getRandomVector();
diff --git a/scene/scene.cpp b/scene/scene.cpp
index 2f1ae2a8..d1b087c1 100644
--- a/scene/scene.cpp
+++ b/scene/scene.cpp
@@ -53,6 +53,7 @@ void Scene::constructScene()
     buildRoom();
     buildLight();
 
+    buildRedBall();
     buildMixBall();
 }
 
@@ -206,8 +207,14 @@ void Scene::buildSceneWithDefaultConfig()
     // bunny->addToPool(m_pObjectPool);
 }
 
+void Scene::buildRedBall()
+{
+    Ball *redBall = new Ball(Vector3::ZERO, Vector3(25, 70, 250), 20, lambMtrlRed);
+    m_pObjectPool->add(redBall);
+}
+
 void Scene::buildMixBall()
 {
-    Ball *mixBall = new Ball(Vector3::ZERO, Vector3(75, 72, 300), 20, MtrlMix);
+    Ball *mixBall = new Ball(Vector3::ZERO, Vector3(-28, 72, 250), 20, MtrlMix);
     m_pObjectPool->add(mixBall);
 }
diff --git a/scene/scene.h b/scene/scene.h
index 34c778c5..16061af4 100644
--- a/scene/scene.h
+++ b/scene/scene.h
@@ -32,7 +32,8 @@ class Scene
     void buildLight();
 
     void buildSceneWithDefaultConfig();
-
+    
+    void buildRedBall();
     void buildMixBall();
 
 private: